Warning: neuroscience weeds.
Every so often we get into discussions about where in the brain consciousness lies. Sometimes it’s asserted to be in the brainstem, other times in the thalamus, sometimes in the parietal lobe, and yet other times in the prefrontal cortex. Myself, I’ve concluded that conscious perception requires activation of a network including sensory cortical areas, the posterior association cortex, and regions in the frontal lobes. In other words, a number of areas in the thalamo-cortical system are necessary.
One interesting data point for this discussion has been the phenomenon of blindsight. Sometimes people sustain brain injuries in the visual cortex in the Occipital Lobe. Their eyes are physically fine, but the cortical region in their brain that processes vision is damaged, so their ability to consciously perceive what the eyes are seeing is reduced or eliminated.
However, often people with this condition, if forced to make a decision about whether something is in front of them, are able to to do so with a success rate significantly higher than chance. Such people are also often able to perceive emotions on people’s faces, even if they have no conscious perception of what they’re seeing. In essence, they seem to have only a vague feeling about what their eyes are seeing.
There have been a number of theories about how this happens, but the one most cited proposes that there are alternate pathways for visual information to reach the patient’s executive centers in their frontal lobes. The majority of the axons in the optic nerve go to the thalamus and then to the visual cortex, but about 10% go to a region in the upper brainstem or midbrain region called the superior colliculus.
The visual processing that happens in this region is interesting because we have no conscious access to it. It’s like a subterranean perception area. None of the axons from the color sensitive cones cells project there, so the sensory images that form there are low resolution (blurry) and colorless. These images typically drive reflexive eye movements including saccades, low level attention impulses, and other functions.
The alternate pathway theory assumes that signals from this region somehow reach the executive centers of the brain, allowing the accurate but “blind” guesses.
A new study by Australian researchers using fMRI has confirmed the existence of this alternate pathway. It appears to go from the superior colliculus, to the pulvinar region in the thalamus, and from there to the amygdala, which communicates emotions to the executive center. This is how the feeling of something in front of the person reaches their conscious perception without the visual part of the perception.
This seems like additional evidence that conscious perception is a cortical phenomenon. If it were in the upper brainstem, we would likely have at least some conscious access to the visual images there. And since the alternate pathway goes through the thalamus, that also seems to rule out that region as a seat for consciousness. (At least by itself, since the thalamus is a signaling hub that the cortical regions use to communicate with each other.)
Of course, alternate explanations are always possible, but we have to keep Occam’s razor in mind.
Unless of course I’m missing something?
69 thoughts on “Blindsight explained and conscious perception”
Thanks, very interesting! There’s a lot of visual processing that we have no conscious access to. That’s probably the #1 reason why machine vision programming is so hard. Here’s how my work in that area goes:
Me: How can I get the classifier to see that this is a cat, not a dog? OK brain, how did you see that this is a cat?
Brain: Because it’s so feline, duh!
Me: No, I mean, for example, what shapes gave it away?
Brain: Catty eyes, catty ears, catty whiskers, and a catty tail. And catty body.
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Haha! Thanks Paul.
Your work sounds fascinating. Have you been following the predictive theories of perception? I’ve been meaning to read Jakob Hohwy’s ‘The Predictive Mind’. I did try to read Andy Clark’s ‘Surfing Uncertainty’, but found the book difficult, both in its physical format (it’s not available on Kindle in the US) and in terms of writing quality. But those theories might provide something to grab onto in terms of how the brain reaches it’s “so feline, duh!” stage.
No, I’m shockingly ignorant about both human vision and machine vision. Our company’s machine vision programmer quit, so now I have to take some crash courses to learn her job. I think my human-vision learning has to start with more basic stuff than overall brain function – stuff like edge detection.
Ah, ok. Sorry, can’t help with how that’s done with ANNs. I do know that organic nervous systems enhance edges in sensory signals using lateral inhibition, where the “pixels” in the center of shape are inhibited but the edges aren’t, making the signals from those edge “pixels” stronger.
Yes but like all consciousness theories theres evidence, real documented evidence, that points in almost every direction. I pointed to scientific research on folks who died and were revived that reveals consciousness after clinical death up to 20 minutes have been documented. Blood flow has stopped and all other activity stops. I think honestly we don’t even have a good definition of consciousness. Some scientists even give up all together and call it an illusion which is just silly in my opinion. I think therefore I am. Is consciousness just experiences we perceive through vision or other senses or is it something more?
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That’s not true. There is evidence of brain activity continuing after the heart stops (legal clinical death), although the claims of actual consciousness continuing is based on after the fact testimony. Like most medical miracle stories, they’re not verifiable.
There is no scientific evidence for consciousness after brain death.
After brain death, I agree. There is evidence the brain continues to function in some fashion for a while after body death (heart stoppage). But so do other parts of the body.
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Let me quote Mark Solms and Oliver Turnbull writes in The Brain and The Inner World:
“We might say, then, that these tiny nuclei [in the brainstem] are the seat of consciousness. On this view, consciousness is generated not by specific cortical zones but by the activation of specific cortical zones by these deep structures.”
The argument isn’t that cortical structures are not involved. It is that the activation of these structures by cells in the brainstem are necessary to produce consciousness. As far as I can tell the subjects in this study had brainstems. 🙂
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One of the problem with the word “consciousness” is that it means a lot of things. I tried to signal my meaning (perhaps not effectively) in the post by saying “conscious perception”.
There are two broad types of consciousness: wakefulness and awareness. You can have one without the other. Vegetative patients often have sleep / wake cycles without an awareness. And we have (limited) awareness when dreaming without being awake.
I don’t think there’s any argument that structures in the brainstem and basal ganglia aren’t involved in wakefulness. But awareness appears to be a largely thalamo-cortical phenomenon. The brainstem’s contribution to this appears to be allowing the higher regions to override its reflexive reactions, which of course is crucial, but by itself insufficient.
The direct-to-amygdala marketing system is not restricted to the visual system, and I suspect that it is the source of a lot grief.
Much of our perception is shaped in the toothier parts of the psyche before it gets to the suits.
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I think “shaped” is a good word.
You stated — “Of course, alternate explanations are always possible, but we have to keep Occam’s razor in mind.”
My response — It would seem we are more complex than we know, the heart also has neurons, neurotransmitters, proteins and support cells, like those found in the brain.
There is also evidence of conscious information without direct learning through complex automated processes that have not been identified.
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Definitely there are neurons all over the body throughout the peripheral nervous system. But the presence of neurons, in an of themselves, doesn’t denote conscious awareness. Most of what happens in the nervous system happens without it.
That’s not to say that the ongoing resonance loop between the body and the brain doesn’t have major effects on our perception and overall cognition.
You stated — “But the presence of neurons, in an of themselves, doesn’t denote conscious awareness. ”
My response — Since we have not isolated the exact cause of conscious awareness how do you know for sure it doesn’t?
We have a century and a half of neurological case studies where damage to the nervous system, either by disease or injury, has been correlated with cognitive impairments. This has accelerated in recent years with brain scanning technologies like EEG and fMRI.
A person can have their spinal cord severed at the neck, their vagus nerve cut, or their cerebellum destroyed, lose senses, and remain conscious. Damage to areas of the thalamo-cortical system appears to be what cause impairments in awareness. Damage to the brainstem often destroys wakefulness.
An excellent source for information like this is ‘The Tell-Tale Brain’ by V.S. Ramachandra, although most books on basic neuroscience covers it in broad strokes.
I am aware of the studies since they fascinate me to no end. And I agree we have accumulated a great deal of information on what can disrupt human cognition.
But to be clear science has not determined what causes consciousness. This is not a denial of what we know, simply a fact of where we are.
An example of how little we know might be someone like, Martin Pistorius.
Or even Daniel Tammet would be a good case study.
Just a thought
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Certainly there remains a vast amount to learn about the brain. We’re probably a century or more from a full understanding. That said, my concern is that people often want to inflate the mystery and ignore what is known to preserve room for fanciful notions.
In the case of consciousness in particular, much of cognitive neuroscience ignores it for more definable problems such as arousal, sensory perception, attention, memory, affects, or metacognition.
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More often, damage to the brainstem causes death, a condition that rules out wakefulness … ;-).
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Or sleepiness for that matter 🙂
I’ve never been surprised by blindsight, because I see the brain as a holistic organ of astonishing complexity. (I see things like blindsight as confirming my view that, whatever mind is, it arises from the operation of the brain as a whole physical machine.)
Something that struck me while reading the post and comments is that we can pick up the electrical signals of the brain from outside the skull. What is the electrical environment like inside the skull? Does that affect anything? Is information exchanged that way?
It’s almost hard to imagine those signals wouldn’t be a part of things, as they’ve always been there, so evolution would have used them if it could. (You may recall I’ve pondered the effect of a “standing wave” on brain operation before.)
Cognition seems weirdly both fragile and robust. Some very minor things (tiny amounts of certain chemicals) can throw it way outta wack (in some cases, in delightful ways). But major damage, such as a stroke or steel rod shooting through, and the brain recovers.
FWIW, this apparently holistic function is why I’ve never been much taken with functional analysis of mind. I think that just results in a rough map of the territory, a corporate org chart, if you will. It’s certainly very interesting to try to determine the mind’s org chart, but I’ve never believed it will lead to accurate reconstruction of the “corporation.”
As we see here, sometimes the mailroom acts like the cafeteria.
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“What is the electrical environment like inside the skull? Does that affect anything? Is information exchanged that way?”
Electromagnetically, it’s noisy. However, the nervous system is “designed” to minimize the effects of interference. Neurons are insulated form each other by glia and their axons with myelin sheaths. (Myelin is white, which is what makes the white matter connecting tissue under the cortex white.)
You’ve probably heard that most newborn behavior doesn’t come from their neocortex because of its immaturity. The reason is that most of the axons in their cerebral cortex aren’t myelinated yet. The resulting interference effectively makes their cortex of very little use at first. On the other side, multiple schlerosis is a disease that destroys myelin, which progressively disables the functionality of the central nervous system. Healthy CNS function minimizes interference.
Of course, some interference does get through, but it’s not clear whether it amounts to more than what comes in from the overall environment such as the earth’s magnetic field, etc. It’s conceivable that all that has some adaptive value, but if so, it would have to be pretty subtle.
On brain waves, a lot of discussion about neurons often makes it sound like they’re lying around waiting to be excited. But that’s not accurate. In reality, they’re firing all the time, in synchrony with brain waves. When we speak of a neuron being excited, we should think of it as firing at higher rate than the overall rate. When we speak of it being inhibited, we should think of it as firing at a lower rate than the overall rate.
I actually think cognition is far more robust than people assume. Yes, messing up its chemical balance can cause problems, but it’s actually surprising how well it often does work despite that.
On holistic function, you might be right. Certainly we have to be careful in assuming we know that region X does Y. Usually all we can say is that region X is associated with Y, or crucial for Y, but X may in fact be one part of a wide network necessary for Y. Still, it’s possible to get carried away with this and ignore what is known. For example, we’re very unlikely at this point to discover that the occipital lobe is not heavily vision oriented.
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“…it would have to be pretty subtle.”
Absolutely, and that’s exactly what I’m suggesting.
As you say, they’re all active, so there are 100-billion signal sources. There may be electrical isolation, but how well does it shield RF EM waves? And since groups of neurons operate together on things, the signal might amplified.
I know it’s speculative, but it almost seems it would have to be a part of it.
“Usually all we can say is that region X is associated with Y, or crucial for Y,…”
Yes, and I agree about brain regions. As you know, those are very plastic. My point is just that things are very interconnected; none of those regions act in isolation.
(Which, from an object-oriented design perspective is kind of the anti-pattern! 😀 😀 )
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Yeah, evolution is a terrible programmer from the point of view of maintainability. A geneticist, who also had some programming experience, once told me that deciphering DNA was like trying to reverse engineer an assembly language program written in the most spaghetti fashion possible, with no meaningful variable names, lots of sections copied and pasted haphazardly with inconsistent modifications, and tons of dead code.
I don’t think neuroscientists should expect the brain to be any better.
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I feel obligated to chime in here. [Someone is wrong on the internet!]
[reaching back to undergrad cell biology … did this change in the last 35 yrs?]
Myelin and other fats do not insulate from electric fields, including radio frequency. Things that insulate from electric fields are things that allow the flow of electrons and or ions —thus the faraday cage. Myelin does, however, insulate one axon from contacting the next, which is important when you have several bundled in a fiber.
The other purpose of myelinating axons is to speed up the signal. You’ll notice pictures of myelinated axons have nodes where one myelin cell (Schwann cell) stops and the next starts. The impulse moving down the axon actually jumps between these nodes. Otherwise, it would take too long for an impulse to go from your foot to your brain.
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Saltatory conduction, it’s called.
We have a disease model for the role of myelin in the CNS: multiple sclerosis.
The conversation at risk of confusing anatomy with physiology. They are related, but not the same thing.
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Myelin does insulate axons from each other, which minimizes signal contamination between them. The reason it speeds the signal in the axon is it minimizes leakage of the signal. (Interestingly, invertebrates reportedly don’t have myelin. It makes you wonder if that’s not one of the factors limiting their intelligence.)
Tests for ephaptic coupling, communication between neurons other than through synapses, haven’t been able to show any consistent effect. Under ideal conditions, the effect is something like 20% of the firing threshold of the destination neuron. In reality, the insulation between the neurons rarely allow such ideal conditions, although there may be some cases of it in the peripheral nervous system.
As an aside, myelin (“white matter”), which is important for brain function, isn’t fully formed in the brain until about age 21. That explains a lot about teenagers and shows why 21 is a good age of majority.
So you can tell your kids they are literally not in their right mind (yet).
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Article in Nautilus on noise and the brain:
There is something called stochastic resonance where weak signals are boosted by the introduction of noise. It is possible that insights and memories not conscious might be brought into consciousness through the introduction fo noise into the system
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“There is something called stochastic resonance…”
Exactly. I’ve even pondered if our (genuine) free will comes, in part, from noise. (See Free Will: Compatibilism, near the end.)
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Thanks Mike! I believe you’ve added support to the brainstem consciousness (BC, or I’ll exhaust myself typing) hypothesis, although I view vision as an unusually complex functionality whose deficits, like blindsight, are very difficult to analyze.
But before discussing BC, I have some questions about the “consciousness network” you propose. As you wrote (italics mine):
“I’ve concluded that conscious perception requires activation of a network including sensory cortical areas, the posterior association cortex, and regions in the frontal lobes. In other words, a number of areas in the thalamo-cortical system are necessary.”
1. Are you saying “conscious perception” as opposed to using the word “consciousness” for any particular reason?
2. Conscious perception necessarily requires the network’s “activation” … are you referring to the processing that resolves the contents of consciousness? Or are you referring to the production of the conscious feelings themselves? This is an important distinction I believe—I’ve noticed much confusion caused by confusing the contents of consciousness with consciousness itself.
3. Where in the network are conscious feelings themselves, like the feeling of a touch, produced? The entire network of structures or a particular structure?
4. If it’s the entire structure, there should be copious observational evidence that injury/incapacitation of any of the networked structures or their connectivity results in an unconscious individual. Can you point to such evidence? If unconsciousness can be so caused, doesn’t your activated network provide numerous unrealized avenues for total anesthesia?
5. What produces the consciousness of ravens?
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1. I am actually using “conscious perception” in a certain way. To me, the word “perception” refers to the neural images that form in the sensory cortices, along with the association mappings that happen in further layers. But I don’t think we’re necessarily conscious of these until it at least reaches the posterior association cortex in the parietal lobe, and possibly not until the frontal lobes access them.
2. I understand the distinction you’re making. (Or I think I do. Maybe you’ll decide I don’t.) The contents of consciousness are produced in many places. But the consumption of those contents is, I think, centered in the action planning centers of the brain, the premotor and prefrontal cortices. I would just note that without the content, there is no consciousness. Even when we think we’re conscious of nothing, the “nothing” we’re conscious of is usually a black silence with calm breathing, or something along those lines. The only time we’re truly conscious of nothing is when we’re not conscious.
3. The perception of the touch is in the somatosensory cortex. I think the feeling of the touch is in the frontal lobes, predominantly the ventral regions from what I’ve read. The feeling is the interpretation of the perception. Emotional feelings are the interpretations of the reflexive reactions from sub-cortical regions.
4. If the frontal lobes are destroyed, consciousness seems no longer detectable. Some reflexive or habitual action may remain, but there doesn’t appear to be evidence of a thinking person left. Of course, some argue that the frontal lobes merely destroy a conscious person’s ability to express that consciousness. Admittedly, this is a difficult distinction to test.
Christof Koch points out anecdotal cases of patients with frontal lobe pathologies who did not appear conscious, but later recovered use of their frontal lobes, reported that they were conscious but merely lacked the motivation to respond. But memories can be recorded in the back half of the brain and later accessed by the front half. It doesn’t mean the recording of those memories were actual conscious events. Again, this is difficult to test.
If the posterior cortices are injured, it can knock out aspects of the contents of consciousness. But remember that without content there is no consciousness. This is why destruction of certain perceptual regions makes some perceptions not just unavailable, but inconceivable to the patient. Hemispatial neglect is the most commonly cited example.
5. As I understand it, the crow corollary to the neocortex is the nidopallium. Crows show intelligence. They can make predictions about the future, which implies imagination, which likely happens in the nidopallium. Whether this amounts to consciousness in the way we have it is, as always, a matter of judgment. (I personally don’t think there is a fact of the matter here.)
I don’t think what we commonly call consciousness is a magic quality of some part of the brain. It’s a nexus of information flows used for predicting the future. That functionality can happen in different places in different anatomies. It’s why a fish who can only predict a second or two in the future can be considered to have a form of primary consciousness, albeit to a far less degree than a mammal.
Thanks for your reply Mike. I cannot locate any information on the effects of frontal lobe destruction, but The Google says (via spinalcord.com) that some of the effects of damage to the frontal lobe “include, but are not limited to:
• Sudden changes in behavior, including aggression;
• Impaired moral judgment;
• Memory loss;
• Reduced motor skills and spatial reasoning;
• Declining intelligence;
• Inability to understand/interpret social cues;
• Impaired language skills;
• Loss of empathic reasoning (ability to relate to the emotions of others); and
• A range of specific syndromes.
Seems like a whole lot of consciousness is implied in that list, but I could find no mention of undetectable consciousness, even in discussions of the effects of a frontal lobotomy.
While I’m taking the time to further reflect on your reply, I notice something of a human consciousness bias here and there, as if consciousness arose only after the maturation of your human “consciousness network” and could not possibly have occurred prior to that. You apparently don’t credit corvids with consciousness “in the way we have it”. How about the family dog? I suppose I could generalize my question into:
6. At what point in vertebrate evolution do you believe consciousness developed?
And I’m talking about fundamental consciousness here, as in a feeling of pain.
On the frontal lobe, I actually dug up the original paper on lobotomies a while back to make sure I understood the procedure and its effects. In it, the connections to the prefrontal cortex are severed, but not the connections to the premotor and motor cortices. The paper cautioned that severing the entire frontal lobes effectively erased the person’s personality. (Although I’m open to the possibility that reflexive and habitual action may remain, as well as perceptual awareness.)
It’s worth noting that the prefrontal lobotomy dramatically blunted people’s ability to feel, separating the connections with the amgydala, a gateway to the lower level midbrain structures. That was actually a large point of the operation. Many patients had psychiatric disorders that made them excitable and difficult to handle. The procedure fell from favor when the public turned against it, but also because medications were developed that could treat those conditions.
On human consciousness bias, I made some clarifications at the end of my last reply, but maybe they weren’t clear enough. First, my view of consciousness is relentlessly functional. It’s a collection of capabilities that individually exist in various locations in the brain. The individual capabilities have been shifted around by evolution over time.
“6. At what point in vertebrate evolution do you believe consciousness developed?”
I think primary consciousness (sentience and mental images) goes back to the Cambrian explosion. All vertebrates have behavior consistent with it, as well as arthropods and cephalopods. Note that this includes a wide variety of brain anatomies. Arthropods and cephalopods in particular are radically different from vertebrates.
I don’t know if you saw my post on the book Consciousness Demystified by Todd Feinberg and Jon Mallatt, but it, along with their earlier work The Ancient Origins of Consciousness, do an excellent job of covering the evolution of consciousness.
All of which is to say is that consciousness doesn’t exist in a particular location or due to a type of neuron. The capabilities that make up what we call primary consciousness can be implemented in a variety of ways. In the case of arthropods and cephalopods, they diverged before the evolution of vertebrates, so their consciousness is an example of convergent evolution.
Mike, I don’t believe you’ve ever responded to my definition of consciousness, “If the brain of an organism is configured as a feeling and that feeling is felt by the organism, that’s consciousness.” That’s consistent with Damasio’s general definitions of consciousness as “the feeling of what happens” and core consciousness as “the feeling of being embodied and centered in a world”. Core consciousness is also referred to as creature consciousness and primary consciousness. Please note that core/creature/primary consciousness is consciousness (!!), not some non-conscious something-or-other that we call primary consciousness, and not some primitive pre-conscious zombie-like reflex sequence.
From the reviews and summaries I’ve read, I’m very much in agreement with Feinberg and Mallatt’s (F&M) neurobiological naturalism (a follow-on I believe, to Searle’s biological naturalism) and I pretty much agree with their evolutionary views, which you cite. Note that F&M cite Bjorne Merker in some of their writing and I suspect that some of their ideas are also shared by Damasio. Merker proposes that the brainstem complex is the seat of consciousness and the massive parallel processing of the cortex, a much later evolutionary development, computes most of the content of extended consciousness and those pre-conscious “images” are sent to the brainstem complex for “display”. More elaborate contents of consciousness, such as with ourselves, aren’t “more consciousness,” they’re more content with more detail. Lets call that “Brainstem Consciousness in a Nutshell”.
From the Feinberg and Mallatt article, “Consciousness is not inherent in but emergent from life” [italics mine]:
“Our own theory of the origin of consciousness is called neurobiological naturalism. In constructing this theory, we pondered which set of neural features led to the emergence of consciousness and then deduced that it originated in the first vertebrate fish and the first arthropods between 560 and 520 million years ago in the Cambrian Period. Fossil evidence from this age documents the rapid evolutionary elaboration of sensory organs, nervous systems, behaviors, and indirectly, cognition. In our emergentist approach to the evolution of consciousness during that time, we related consciousness to the first appearance in brains of mapped, mental simulations of the world and of the first affects (“emotions”), all of which helped the conscious animals to target their interactions with the world. … we are confident that both consciousness and life—and all the myriad emergent properties of living systems—evolved continuously and without any breaks that demand miracles to fill.”
And, in an interesting footnote:
“We do not agree, however, with [the] view that consciousness needs a cerebral cortex as in mammals.”
Apparently F&M disagree with your own theorizing. I continue to feel that the consciousness you’re discussing is, more often than not, human consciousness. You wrote, “The perception of the touch is in the somatosensory cortex” but perhaps you don’t realize that you’re ruling out the possibility of a touch feeling in pre-cortical brain architectures and also disagreeing with F&M. You write that “[Consciousness is] a collection of capabilities that individually exist in various locations in the brain,” yet you specify various “locations” that are decidedly post-Cambrian.
The sheer anatomical complexity of your proposal plus the never mentioned challenge of presenting a single unified conscious experience lend me to suspect that it might be ripe for an Occam shave. 🙂
Ugh. I meant to reply here, but ended up replying at the bottom of the thread.
I think it has been known since the research of Wilder Penfield or longer that activation of areas in the cortex through the ARAS is required for consciousness. The network is the reticular formation, the ARAS, and the cortical areas. Without the cortex the level of consciousness is basic, perhaps involving only a sense of being in a body and awareness of pain.
I’m not familiar with Penfield’s specific work, but most of what I’ve read ties the ARAS to arousal. The general thought in neuroscience is that the insula cortex (and surrounding regions) is involved in a sense of bodily self, and it and the anterior cingulate cortex are necessary for the conscious experience of pain. Damasio uses the phrase “proto-self” for the primordial body image in the brainstem, which I think is a good term.
It can be confusing because the ARAS and midbrain may be sufficient for affect displays, outward behavior we normally associate with feeling states in a healthy person, such as facial expressions, crying, moaning, etc, but that can be solely reflexive in nature.
It is remarkable that neurobiologists have identified locations in the brain where mental functions occur: the occipital lobe for vision; Broca and Wernicke areas for language; parietal lobe for sensory/motor functions (the famous “homunculus”); temporal lobe for hearing; olfactory bulb for smells.
Looking for a location for consciousness is surely a mistake. When we are conscious we are aware of what we see, speak, hear, smell, touch and move around in. Consciousness is awareness of these awarenesses (a good definition of consciousness as has been recognized); so consciousness must be widely distributed in the brain, connecting and coordinating the locations of of these various neural/mental functions.
I think consciousness is like a mother hen who gathers her chicks around her and tries to keep them in order. But she would be fooling herself if she thought she was the executive of the henhouse living in her own boardroom. (She would know that if all her chicks died—but then, of course, she would be dead too!)
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Excellent point. I often say that consciousness is actually a suite of capabilities. We can identify crucial regions for each of those capabilities, but there’s no one region where all of them reside.
Attention is a multilevel capability centered on the pulvinar in the thalamus. Memory happens throughout the brain but appears coordinated in its construction by the hippocampus. Imagination and metacognition seem focused in the prefrontal cortex, but are heavily dependent on sensory imagery and associations from throughout the neocortex. The sense of self seems focused in the parietal-temporal junction and/or insular cortex.
In some ways, using the word “consciousness” as anything more than the private experience of the system with these capabilities confuses more than it clarifies.
I don’t know, but I get the sense that you and I see things more similarly than not. So consciousness as the hen trying to reign in its chicks, and then dies without them? Alright. The analogy that I currently use is that consciousness exists as a “computer” that is outputted by a second such computational machine, which is the central organism processor commonly referred to as “brain”. Just as wind exists as an output of a fan, here consciousness exists as an output of a neuronal based machine.
I’ve been discussing this with Wyrd over at his site in a post of a series of posts regarding computation: https://logosconcarne.com/2015/11/13/information-processing/
Our commentary begins here: https://logosconcarne.com/2015/11/10/transcendental-territory/#comment-27915
If you do check this out, as well as have a modern phone, I recommend that you select the text and listen through an app such as Speechify. Currently our dialog runs about 40 minutes. In truth I’m only just now beginning to get into the meat of my model. I expect (or hope) that Wyrd and I will be discussing this for weeks longer (if not for years).
Have you found much use for Speechify yet, or do you find that you need to keep actively reading text?
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I’m still a reader. Generally if I don’t have time to read it, I’m not in a position to pay attention to it while listening. If I spent a large part of my day doing physical work, it might be different.
And it sounds like I might have mentioned that my attention tends to stray when I listen to things anyway. I do listen to podcasts when walking, but my time doing that is limited, and the podcasts don’t require (much) prep work.
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Well keep it in mind Mike. My own life has far more obligations than I would like, or at least during the week. Blogging can thus represent what I want to do rather than what I need to do. Thus when I’m driving, doing laundry, or even just resting my eyes, this tool helps me keep up.
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It’s a pleasure to see eye-to-eye with someone about the nature of consciousness. Attention and imagination can then be shifted to the question of how consciousness is best used.
(I’m not a fan of the term “metacognition”; it seems to me “cognition” is sufficient for referring to one of the major functions of consciousness.)
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I think the term “metacognition” is a play off of terms like “metadata”, data about data. In the case of metacognition, it refers to cognition about cognition. In this case “meta” seems to mean “about.” Given the etymology of “meta” as meaning “beyond”, as in metaphysics being beyond physics, I’m not sure how this usage arose, but I think the resulting connotations make some people uneasy. When I use it, I’m referring to introspection or self reflection.
I think the way you use the term is straightforward and perfectly acceptable.
Phil Ashmore’s account of the origin of the term “metaphysics” is the one I learned many years ago:
“I was told that the term “metaphysics” arose simply because early librarians , when putting Aristotle on the shelf, had his physics first, then his other works further down the shelf and so called them the “metaphysics”. Can this be true?
Michael Stevens, Auckland, New Zealand
“Metaphysics is so called because the name was posthumously given to Aristotle’s ‘First Philosophy’, a work which he wrote after his ‘Physics’, hence the Greek metaphysika ‘after-physics’. This work dealt with the first principles of existence, such as being, substance, essence, the infinite, ultimate reality. At various times the whole range of philosophical inquiry has been classed as ‘metaphysical’ and the contrast between the disciplines of science and philosophy is relatively modern.
Phil Ashmore, London England”
(This exchange appeared in The Guardian. I just found it on the Internet)
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“Please note that core/creature/primary consciousness is consciousness (!!)”
So, you might find this frustrating, but all definitions are just a convention. The only consciousness we have access to is our own subjective experience, which includes all the capabilities of the human version. Decreeing a particular subset as “consciousness” is an inevitable value judgment on which parts are important. This is why careful writers qualify exactly which version of consciousness they’re discussing. Many people would insist that introspective self awareness is crucial for “real” consciousness. They’re not right and they’re not wrong, because there is no fact of the matter on this.
“Apparently F&M disagree with your own theorizing. ”
I’ve read F&M at length in two books now. I’m pretty familiar with their views. You’re focusing on isolated snippets that bolster your case. But similar to the points I made above, F&M are clear that consciousness can come about in a variety of ways. That’s what they mean in the quote about a cortex not being necessary. Consider this excerpt from their first book:
To your last point, I’ll just quote Einstein: “Everything should be made as simple as possible, but not simpler.” 🙂
Mike, I’ve searched amazon and elsewhere but am unable to locate a recent copy of Merriam-Webster’s Conventionary. I should also look for their Opinionary. [Another joke Mike]. I prefer the old fashioned practice of believing that words can be assigned precise meanings so that, when we use them with other folks, we can be reasonably certain that we’re discussing the same thing.
Your phrase “… all the capabilities of the human version” of consciousness is a reference, once again, to the CONTENT of consciousness, which varies considerably from one type of conscious organism to the next. The definition of consciousness itself must specify what is common to all instances of consciousness, otherwise we most unfortunately must rely on Conventionaries and Opinionaries and we’ll sacrifice all meaningful discourse on the subject. We seem close to that already with imprecise usages of the word consciousness that are all over the map. We don’t define “automobile” as a vehicle with a chrome grill, because some have one and some don’t—the chrome grill is not a common attribute and is not definitional. You’ve correctly pointed out that no consciousness exists without content, but consciousness and the contents of consciousness remain two distinctly different things.
I reiterate that an animal feeling a feeling is conscious. Any animal feeling any feeling is a conscious animal.
I quoted F&M’s (a favored source of yours) remarks about the evolutionary origins of consciousness and, rather than addressing the implications for your consciousness hypothesis, you responded by quoting F&M’s remarks about mammalian consciousness. I don’t understand your abrupt change of subject, but I’ll respond with the significant evolutionary implications Real Soon Now.
For now, I must say that I am appalled by the cited experimenters’ outright cruelty to decerebrate mammals, an unquestionable ethical lapse owing to both their demonstrated hubris and obvious unrecognized bias. Neuroscience at this time does not know where in the brain consciousness is produced! At present we have multiple competing hypotheses on the issue, but no definitive proof! NONE! The Merker paper you’ve been reading makes an impressive observational and evidence-based case that these experimenters’ understanding is incomplete and possibly incorrect. They assumed without incontrovertible proof that decerebrate mammals were unable to feel pain and they interpreted the behaviors resulting from their torture as mere zombiefied reflexes. Incredible! Horrible!
“In summary, noxious stimuli can induce many painlike behaviors in mammals without participation of the cerebral cortex and thus without any actual pain.”
There’s simply no way in hell that their “thus without any actual pain” assumption has been conclusively demonstrated. No way!
“The definition of consciousness itself must specify what is common to all instances of consciousness,”
The population of instances of consciousness depends on which definition you’re using. If we define it as metacognitive self awareness, only humans and a few other primates are conscious. If we define it as responsiveness to the environment, everything alive qualifies. (And yes, people do use that definition.)
“There’s simply no way in hell that their “thus without any actual pain” assumption has been conclusively demonstrated. No way!”
Check out the discussion that James and I had below.
“The population of instances of consciousness” is like the population of instances of chrome grills. If we define consciousness as chocolate cake, it’s sweet and tasty.
Metacognitive self-awareness is a human content of consciousness, not consciousness itself. And if consciousness is intelligence/pattern matching and the like, recall that we knew a few decades ago that nearly 100% of that claimed “consciousness” is actually unconscious cognitive processing that is in no way accessible to consciousness.
If a group of scientists viewed a film of rat behavior while the rats were being tortured, followed by viewing a film of rat behavior while the rats were being tortured after a brain surgery, they would conclude the rats were responding to pain that they felt in the second instance, just as in the first.
Since when are rat and human brains and metabolisms considered identical? Drug testing on rats frequently shows results that don’t hold up when tested by humans. The conclusion that what goes for the human brain goes for the rat brain is invalid.
… when tested ON humans, of course.
It’d be nice if my typo correction would end up under my typo.
We do have to be careful about reaching conclusions about the human brain from animal tests, or vice-versa. However, everything in the human brain has evolutionary precedents. There are similarities between all nervous systems at the neuron and synapse levels. All vertebrate brains follow the same broad structure (forebrain, midbrain, hindbrain, cerebellum, etc). And all mammalian brains are even more similar. All mammals, for instance, have a cortex.
We do have to be careful that we limit our conclusions between species that are similar in the areas we’re drawing conclusions on, but if we start reflexively saying that results in one species tell us nothing about others, then most of brain science goes out the window.
My point is that we should be particularly careful to be absolutely certain that feeling pain is impossible before we inflict pain on other creatures in an experiment. As regards the brain structure that produces feelings, multiple hypotheses exist but there is no conclusive evidence at this point as to which hypothesis is correct. Intentionally inflicting pain in an experiment, even if consciousness of the pain is considered unlikely, is an ethical lapse.
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I agree with your sentiments here, though apparently science today turns a blind eye to that sort of thing. (Hey, another variety of blindsight! 🙂 ) It would take a pretty clueless scientist to believe that what’s done to mice and other mammals in the name of science is not painful to them. I suppose scientists continue on with a vast array of such practices from the presumption that more good will come than the harm that will be expended. Of course that presumes that the human deserves such sacrifices. Why? Well because this is us and that is them, of course. Anyway these circumstances aren’t Mike’s fault. You might blame him for not being a devout animal welfare activist however, but then that goes for the vast majority of us.
In truth I suspect that whatever pain that scientists inflict upon their subjects, it’s minuscule when compared against what humanity in general inflicts upon their pets and their livestock, including standard animal tests to show that various consumer products won’t hurt us. I can only go from my own perceptions, but I get the sense that the worst I could ever feel would be millions of times stronger than the best I could ever feel. If that’s at all true then it might very well be that the emergence of sentience has been a horrible tragedy for what exists on Earth in general — the bad side to conscious existence might utterly dominate the good side of it.
You and I should talk in detail some time about the nature of our models. Apparently each of us propose sentience based definitions for the humanly fabricated “consciousness” term. That’s a start at least. Then if things go as normal the wheels should come off. But perhaps not. And even if so, we might still have some fun!
Actually Philosopher Eric, I don’t blame Mike, or anyone else, for anything. I’m disturbed by the ethical lapse of the experimenters in the cited study, but we all know causing suffering to animals of all sorts, including humans, is one of humanity’s favorite things. Blindsight indeed!
I do think it’s worth pointing out that the list of “Reflexive responses in decerebrate mammals (… for example, rodents pushing away objects and syringes from the mouth, or lick or guard injured site, vocalize or jump)” is wrongly concluded.
Regarding consciousness defined as sentience, it’s nice to have some company. I’ve laid out my views about consciousness in this and other threads on Mike’s blog and occasional outrages on Schwitzgebel’s “The Splintered Mind” …
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If you’d like to discuss consciousness further in ways not appropriate for blogs, I have an email address for discussing the ERL hypothesis described in my “Einstein’s Breadcrumbs” paper: email@example.com … I check it once a week or so.
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Sounds good Stephen. It would be nice to know where we see eye to eye so that we might build from there. When you were first looking around here I think that I did take a quick look at your Einstein’s Breadcrumbs. At the time it must have struck me as being a bit off, though I don’t recall the specifics of that. And I haven’t noticed problematic issues in your discussions with Mike so maybe not. Fortunately a sentience based consciousness is a great commonality, which I doubt that I realized then.
Usually my discussions are with people who don’t have their own theory to sell. Here I’ve noticed that people often feel a need to “beat me”, as in “Ha, you don’t actually have anything important to say!” It’s obviously difficult to teach someone the nature of your ideas when they don’t want to understand. I have had better luck with Mike, and believe that each of us have benefitted from our lengthy discussions, but it’s still difficult. To help me most he’d need a working rather than lecture level grasp of my ideas. Hopefully some day.
With you as another passionate theorist there should be a different dynamic however. We should naturally enjoy where our ideas correspond, but should also find contradictions disturbing. In the end there may be various unresolvable differences that, right or wrong, we’re just too invested in to alter.
One thing to realize about me is that my ideas do not exist at the neuroscience level, but instead concern big picture conceptual models. (This has been a point of contention between Mike and I given how smitten he is with neuroscience.) My analogy here is that neuroscience today is kind of like studying each part of a car’s motor in the attempt to decide how the whole thing functions together. While neuroscience is certainly important for what it does, studying individual brain parts should not provide a big picture grasp of general function. And without such theory we shouldn’t grasp individual brain parts very well either.
I’ll shoot you an email sometime, or you could hit me here if you like: firstname.lastname@example.org
“In summary, noxious stimuli can induce many painlike behaviors in mammals without participation of the cerebral cortex and thus without any actual pain.”
How would they know that?
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F&M rely on this report: Recognition and Alleviation of Pain in Laboratory Animals
…which itself ultimately extrapolates from human report studies. In humans, if the pathways between the insula cortex and the anterior cingulate cortex is severed, the person doesn’t experience pain. So it’s a cortical event in humans. The logic is it’s also a cortical phenomenon in mammals.
With that in mind, F&M define certain behaviors that do not indicate pain…
…and those that do.
The criteria might work with mammals but it might be flawed for other animals.
“For example, the possibility of ﬁsh experiencing pain has been dis-missed because human pain is experienced in parts of the cerebral cortex whereas ﬁsh lack this structure (Rose 2002). If one accepts this argument then the possibility of pain being experienced by any invertebrate must be dismissed because none has a central nervous system (CNS) built on the vertebrate plan. According to the same logic it could be suggested that because crustaceans or cephalopods lack any of the visual system found in humans they must be blind. This is not the case as both have a well-developed visual ability, each based on an entirely different CNS and receptors. Thus clearly the same function can arise in different animal taxa using different morphology, and it appears to be illogical to accept this reasoning for some experiences but to dismiss it for pain (Elwood et al. 2009)”
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Definitely the conclusion that pain is experienced in the cortex only applies to mammals.
Invertebrates and vertebrates diverged from each other before the evolution of brains (or spinal cords), so the brains of arthropods are completely different. I’m not sure how much is known about where in their central ganglion is does happen. But we can assess the degree to which they experience pain by the behavior criteria listed above.
However, most of the behavior listed in the the paper you linked to matches the reflexive decerebrate behavior and are probably not good indicators. Although the ones below likely are (they match F&M’s above):
Fish pain is interesting and controversial. They do appear to have nociception, but as the various sources indicate, that doesn’t necessarily mean they feel pain. Many species don’t have c-type fibers, which provide the signals for ongoing pain. Some biologists use the lack of cortex argument to argue that they don’t feel pain.
However, F&M list fish species meeting many of the behavioral criteria for feeling pain and pleasure. They conclude that fish probably feel sharp pain, the kind felt while an injury is being incurred, but probably not the long burning agonizing sort of pain land animals can feel.
Regarding the experimental pain conclusions cited by F&M, here’s a section from Merker’s “Consciousness without a cerebral cortex” … certainly challenges the F&M reflex conclusions. The PDF is available on the internet. I removed the copious parenthesis-enclosed references to shorten the quote. Worth consideration.
“All of the behaviors just mentioned have also been exhibited by experimental animals after their cerebral cortex has been removed surgically, either in adulthood or neonatally. Best studied in this regard are rodents. After recovery, decorticate rats show no gross abnormalities in behavior that would allow a casual observer to identify them as impaired in an ordinary captive housing situation, although an experienced observer would be able to do so on the basis of cues in posture, movement, and appearance. They stand, rear, climb, hang from bars, and sleep with normal postures. They groom, play, swim, eat, and defend themselves in ways that differ in some details from those of intact animals, but not in outline. Either sex is capable of mating successfully when paired with normal cage mates, though some behavioral components of normal mating are missing and some are abnormally executed. Neonatally decorticated rats as adults show the essentials of maternal behavior, which, though deficient in some respects, allows them to raise pups to maturity. Some, but not all, aspects of skilled movements survive decortication, and decorticate rats perform as readily as controls on a number of learning tests. Much of what is observed in rats (including mating and maternal behavior) is also true of cats with cortical removal in infancy: they move purposefully, orient themselves to their surroundings by vision and touch (as do the rodents), and are capable of solving a visual discrimination task in a T-maze.
The fact that coherent and well-organized molar behaviors are elicited by local stimulation in the mesodiencephalic region of intact animals and that coherent motivated behavior under environmental guidance is displayed spontaneously by animals lacking a cerebral cortex means that the neural mechanisms required to motivate, orchestrate, and provide spatial guidance for these behaviors are present in the parts of the brain that remain after decortication. Some aspects of these behaviors are dependent upon basal ganglia and basal forebrain functions remaining after the loss of their principal (cortical) source of afference, whereas the basic competences of decorticate animals reflect the capacity of upper brainstem mechanisms to sustain the global patterning, emotional valence, and spatial guidance of the postures and movements of orienting, defense, aggression, play, and other appetitive and consummatory behaviors. The particulars of the dependence of these behaviors on key structures located in the mesodiencephalic region has been repeatedly reviewed.
It is into the premotor circuitry of these ancient and highly conserved upper brainstem mechanisms that a wide range of systems place their bids for “where to look” and “what to do,” irrespective of the level of sophistication of any one of these “bidding” systems. Each of them has independent access to effectors, and their upper brainstem interactions are not infrequently mediated by collaterals of such projections. The cerebral cortex is one prominent input to this system through the direct and indirect fiber projections emphasized in the foregoing discussion and sketched in Figure 3. This relationship is, however, not a one-way affair. In fact, the manner in which the telencephalon is interfaced and integrated with the mesodiencephalic control system adds further definition to the central role of upper brainstem mechanisms in conscious functions.”
From Scientific American Mind, “When Blindness Is in the Mind, Not the Eyes” of 2008 (https://www.scientificamerican.com/article/when-blindness-is-in-the-mind/):
“Messages from the retina of the eye get transmitted along the optic nerve before diverging into two parallel anatomical pathways, which we shall call “old” and “new” pathways to indicate their evolutionary sequence. The old pathway, also called the where pathway, goes to a structure called the superior colliculus, which forms a bump on the roof of the brain stem, the stalk that emerges from below the brain and continues as the spinal cord. The colliculus helps to determine the location of an object. … The other pathway, the newer one, as we shall see, is required for identifying an item, even though it is incapable of locating it or orienting to it.”
In case that’s not sufficiently clear, look up a diagram of the optic nerve “wiring” you’ll see the brainstem connection of the “old” pathway.
In Werblin and Roska’s 2007 Scientific American article, “The Movies in Our Eyes” we learn that:
“The retina actually performs a significant amount of preprocessing right inside the eye and then sends a series of partial representations to the brain for interpretation. … Overall, we have found that specialized nerve cells, or neurons, deep within the retina project what can be thought of as a dozen movie tracks—distinct abstractions of the visual world. Each track embodies a primitive representation of one aspect of the scene that the retina continuously up dates and streams to the brain. One track, for example, transmits a line-drawing-like image that details only the edges of objects. Another responds to motion, often in a specific direction. Some tracks carry information about shadows or highlights.”
In other words, the retina of the eye, which is evolutionarily a projection of the brain, can be seen as possessing limited cortical-like processing. Those “tracks” are transmitted to the brainstem complex via the “old” pathway.
Per Merker’s paper, “Consciousness Without a Cerebral Cortex” visual experience in the absence of enhanced cortical processing is limited to “the ability to orient to and approach the location of moving visual stimuli in space” but subcortically generated visual experience decidedly exists:
“Complete removal of the posterior visual areas of one hemisphere in the cat (parietal areas included) renders the animal profoundly and permanently unresponsive to visual stimuli in the half of space opposite the cortical removal. The animal appears blind in a manner resembling the cortical blindness that follows radical damage to the geniculostriate system in humans. Yet inflicting additional damage on such a severely impaired animal at the midbrain level restores the animal’s ability to orient to and to localize stimuli in the formerly blind field.”
“… adding a small amount of damage in the brainstem to the cortical damage “cures” what appeared to be a behavioral effect of massive cortical damage. The restored visual capacity is limited essentially to the ability to orient to and approach the location of moving visual stimuli in space. Visual pattern discrimination capacity does not recover after the midbrain intervention, though the midbrain mechanism can be shown to play a role even in such tasks.”
Based upon all the experimental and anatomical evidence above, it seems we can uncontroversially conclude that the brainstem “sees” and produces visual experience, as Merker states.
Consult the individual papers for experimenter source attributions.
In the post above, I noted the visual images in the superior colliculus. But the phenomenon of blindsight happens because we don’t have conscious access to those images. Am I missing something in the Scientific American quotes that contradicts that understanding?
I can’t comment too much on the Merker paper, not having read it in detail. I just downloaded it and looked at the description of the cat stuff, but the details I read don’t convince me that they managed to restore conscious access to the visual field, just that some limited capability was restored. Scanning the evidence the paper cites, too much of it seems based on observed affect displays, which as F&M discussed, haven’t been successfully linked with conscious states.
Mike, it’s nice to know you’ve at last read Merker’s most significant paper. From my own experience, I believe a single reading is insufficient … it’s so chock full of meaningful ideas and experimental and observational evidence that more than one pass is required to fully appreciate it. By the way, you must realize that your claims of cortical consciousness coupled with the lack of integrated cortical development and operation at birth means that you believe that all human babies are born without consciousness and remain in that apparently zombie-like condition for months to years. I suspect that parents everywhere would contest that conclusion based solely on their own abundant close observational evidence.
You responded, “… the details I read don’t convince me that they managed to restore conscious access to the visual field, just that some limited capability was restored.”
Limited capability to do what? Did you miss these statements: “… restores the animal’s ability to orient to and to localize stimuli in the formerly blind field” and “The restored visual capacity is limited essentially to the ability to orient to and approach the location of moving visual stimuli in space.” Orienting to moving visual stimuli certainly demonstrates limited conscious access to the visual field to me.
And you wrote: “… too much of [the evidence] seems based on observed affect displays, which as F&M discussed, haven’t been successfully linked with conscious states.” Note that “Affect is a concept used in psychology to describe the experience of feeling or emotion,” (Wikipedia and a host of others). Apparently F&M hold to the view that affect displays are unrelated to affect experience, as their reflex interpretation of the animal responses to the horrific experimental infliction of pain implies. They seem correct on some points, but their infallibility remains to be demonstrated.
Mike, I’ve noticed that you are consistently dismissive of any and all evidence that challenges your consciousness hypothesis, which I find strange, considering that we should always strive to understand contrary evidence in order to improve and correct our own always provisional hypotheses. At times I get the impression that if God himself gave you a document asserting that he placed consciousness in the reticular structures of the brainstem complex, you’d object that His document wasn’t properly notarized … 😉
[That’s a joke Mike!]
Stephen, I do hope to go through the paper more carefully at some point. However, I’m not a professional neuroscientist, so I’m going to have to put a lot of weight into the overall field’s evaluation of it.
On babies, it’s worth noting that their cortex isn’t completely nonfunctional. Most of their white matter axons aren’t well myelinated yet, and they’re still undergoing synaptogenesis. This seems compatible with the fact that we can’t remember the first couple years of life.
Are they conscious? I suspect a newborn’s consciousness is minimal, despite parent’s emotions. But by 2-3 months, they seem far more aware of the world.
On the cats, I read those statements. My issue is that, given we’re talking about an animal that still has most of its cortex, we can’t know what they’re consciously seeing. It could still be a variation of blindsight. I’m also a bit leery of the amount of interpretation that seems involved. At some point I’d like to dig up the cited papers and get more details.
“Mike, I’ve noticed that you are consistently dismissive of any and all evidence that challenges your consciousness hypothesis,”
I have the same impression of you. I should note that my conclusions come after reading a ton of neuroscience from numerous perspectives in the field. It’s not my consciousness hypothesis. As you’ve noted before, the vast majority of the field see consciousness as a cortical phenomenon. It doesn’t seem to me like you’ve done a fair investigation into why so many working neuroscientists see it that way.
Maybe it will help if I, again, note that I think there are reflexes arcs in the brainstem and low resolution sensory images in the superior and inferior colliculi. As I noted in the OP, we don’t have introspective access to these images, but they could be regarded as a sort of subterranean consciousness.
In pre-mammalian species, this is where the endpoint visual images were maintained. I can see why you might believe that it must be the same in newer species, but that assumes that evolution is a clean engineer. It isn’t. Things get duplicated, bypassed, and crazily wired. And based on what I’ve read, I tend to think that even for anamniotes, the forebrain was a crucial piece of consciousness.
And as I’ve also noted, consciousness doesn’t exist in just one place and via just one mechanism. Do you think arthopods are conscious? Their brain organization is nothing like a vertebrate’s, yet many of them meet the behavioral criteria for consciousness, even F&M’s stringent ones, What are the implications for your idea that all the visual imagery is piped down to the brainstem, if a conscious creature doesn’t have a brainstem?
As for God, I’m a skeptic. He’d need to provide evidence he wasn’t a hallucination first, then evidence for whatever he was asserting 😀
“On babies, it’s worth noting that their cortex isn’t completely nonfunctional … I suspect a newborn’s consciousness is minimal …”
Mike, your hypothesis claims that consciousness requires the coordinated functioning of several interconnected and mature cortical areas, a functionality that’s not at all developed in newborns whose brains are busily eliminating neurons. Your own hypothesis mandates a “not conscious” determination in that situation. Yet, you apparently want babies to be conscious and suspect a minimal consciousness. Where would that minimal consciousness come from?
“… the vast majority of the field see consciousness as a cortical phenomenon.” I believe that, precisely stated, the majority of the field hypothesize cortical consciousness, for which there is no evolutionary, experimental or observational evidence. The hypothesis is additionally challenged on many fronts, Damasio, Merker et al for starters. I would welcome your citing of any neuro-specialists that have confirmed that consciousness is a cortical phenomenon along with some summary of their compelling evidence case. Please include F&M’s incontrovertible and experimentally repeated (by others) evidence of their mammalian cortical consciousness claim. If it’s case-closed, as you imply, perhaps we can relieve a large scientific population of their compulsion to continue researching and publishing. And let Eric Schwitzgebel know too … he too understands the majority-minority status of the competing hypotheses but he keeps muddling around believing the issue is unresolved.
I’ve noticed that you’ve ignored my mentions of “The Binding Problem” and I would appreciate your solution. The problem doesn’t exist for the brainstem consciousness hypothesis. The proposed solutions would probably interest Occam, speaking of whom, what’s your analysis of this famous Libet experiment, where cortical consciousness is assumed:
As described in Stuckey, et al in “Reversing the Arrow of Explanation …” paper:
“Libet discovered that if we directly stimulate the appropriate spot on the somatosensory cortex that is connected to the hand and then 150 milliseconds later we stimulate the hand itself, the subject reports the hand stimulus as coming first. This is very puzzling because the ‘real external’ time to process both signals is the same. Somehow the brain flipped the order of events in conscious experience.”
You’ve claimed that the somatosensory cortex produces the consciousness (the feeling) of a touch. If that is the case, why isn’t the stimulated cortical touch perceived immediately? Tracing the nerve paths, it’s obvious that signals from the touch on the hand itself reach the brainstem complex before being forwarded to the cortex, so, once again, no puzzle exists for the brainstem consciousness hypothesis. Along with the Binding Problem, I’m sure the proposed Backdating Mechanism would feel the sharp edge of Occam’s razor.
Mike, everything we know about massively parallel cortical operations supports the thesis that the cortex resolves details of the content of consciousness but the fact remains that the location of the brain tissue that actually and finally produces a conscious feeling is unknown except, of course, for the solid evolutionary and experimental evidence you’re about to provide per my request just above.
Regarding your closing question, “What are the implications for your idea that all the visual imagery is piped down to the brainstem, if a conscious creature doesn’t have a brainstem?”, I should point out that the brainstem hypothesis, first and foremost, applies only to animals with brainstems.
I’ve referenced the evidence multiple times in multiple threads going back to our initial conversation on Eric’s blog. At this point, I fear there is nothing that I could provide that would convince you, and my time is too limited to keep digging up details. I’d be happy to recommend some books if you’d like.
I would note that if you actually took Damasio’s position, we wouldn’t be that far apart. Damasio calls what forms in the brainstem the protoself. In his view, the actual core self requires the cerebrum, with the autobiographical self definitely requiring the cortex. I haven’t read Merker enough yet, but I suspect his views are going to be similarly nuanced. Your position would be stronger if you asserted that the brainstem had a protoconsciousness, or that it was the origin of feelings. There would likely still be differences between us then, but it might just come down to what we were willing to label “conscious.”
But your position that the brainstem is where consciousness in full resides is one that I don’t think even people like Jaak Panksepp, Mark Solms, or Douglas Watt would endorse. I know Panksepp in particular saw aspects of lower level consciousness in the brainstem, but had no trouble admitting that many other aspects of it were in the cortex, for mammals.
All of which is to say, I think we’re simply going to have to agree to disagree on this, at least for now.
Mike, I’m sorry you’re abandoning our conversation about the two competing hypotheses regarding what structure(s) in the brain produce consciousness. Although you seem to believe that “there is nothing that [you] could provide that would convince [me]”, your exit is strangely timed immediately after my request for that evidence that you have claimed supports the cortical consciousness hypothesis. Convincing me requires coherent quality evidence.
You may believe you’ve “referenced the evidence multiple times in multiple threads … on Eric’s blog,” but you haven’t, nor has anyone else. Or, at least, I can’t find it—and I’m sure I would have noticed—after all, I’m the clown that periodically mentions the “evidence-free cortical consciousness hypothesis” on his blog. No one has responded by contributing actual evidence to Eric’s blog because there isn’t any. I am somewhat surprised that F&M’s crucial evidence for mammalian cortical consciousness isn’t readily available for you to cite since you’re so familiar with, and rely so heavily on, their analysis. And I don’t understand why you don’t take this opportunity to present your explanations for the Binding Problem or explain Libet’s experimental results which, as seems obvious, lend support to the brainstem consciousness hypothesis.
I had already prepared some commentary about the evolutionary challenges to the cortical consciousness hypothesis so I’ll present it here. Although you remarked that I seemed to be “… focusing on isolated snippets that bolster [my] case,” in fact, I had simply Google’d for and downloaded three F&M article PDF’s, their “Consciousness is not inherent in but emergent from life” among them. The quote I copied from that paper, beginning with “Our own theory …” is on page 4. Based upon their views, which I find credible and consistent with those of many other specialists, it seems reasonable for us to conclude that consciousness existed in pre-cortical brains. Rather than the very earliest instances, however, let’s focus on an anatomy that’s a direct evolutionary precursor to our own, with what is now a lower brain structure—the Brainstem Complex (BCx)—sitting atop a central nervous system, all dedicated to the task of keeping alive an animal that’s in motion in the world.
Relative to the cortical consciousness hypothesis, the challenging evolutionary questions to address are these:
1. Why did the BCx undergo such a radical change as a complete loss of consciousness functionality, considering that, per evolutionary theory, body structures critical to staying alive (brainstem, heart, lungs, …) are not duplicated, but are typically conserved and enhanced? I use the word “critical” because animals capable of consciousness don’t lead normal lives when bereft of consciousness but will die after a period of doing nothing at all if consciousness is not restored.
2. How was the relocation of consciousness production from the BCx to the newly evolved cortical structures accomplished? Intermediate steps?
3. Why would a unified production of consciousness be supplanted by a distributed consciousness architecture requiring complex coordination, not only among the disparate cortical locations of consciousness creation but with the still functioning BCx as well?
4. How could that complex coordination solution evolve in a smooth fashion that didn’t disrupt the already existing unified stream of consciousness?
Your answers to questions 2 through 4 would explain the evolution of your solution for the Binding Problem.
Since the eyeball is a projection of the brain, we see that the pre-cortical brain produced neurons with cortical functionality in the retina. Those neurons resolve visual characteristics that are continuously delivered to the BCx via the “old” pathway to produce visual consciousness, so the continued evolution of cortical tissue (as cortex) to better resolve conscious content can be easily understood as a continuation of that evolutionary strategy.
You’re correct in observing that my generalization of the brainstem consciousness hypothesis goes somewhat beyond the thinking of others. Damasio, for instance, believes in some cortical consciousness because conscious images can be found there. I simply propose that those resolved cortical images are pre-conscious and transmitted to the brainstem which incorporates them in its continuously updated conscious stream.
Mike, convincingly responding to the problems and questions I’ve presented is crucial if cortical consciousness proponents like yourself wish to improve their hypotheses by removing errors and addressing identified problems and weaknesses. I’ve presented my arguments to help you in that effort. This isn’t a contest and it’s not at all about being “right.” We don’t have to agree to disagree—we can and do improve our ideas and our understanding this way. There’s no disgrace in revising one’s hypotheses or adopting the ideas of others. That’s how we make progress in knowledge and understanding. And I don’t believe I’ve been dismissive of your evidence that challenges the brainstem consciousness hypothesis because, in reviewing this entire thread, I cannot find any such evidence.