Split brain does not lead to split consciousness – University of Amsterdam

I’ve talked before about Roger Perry’s famous split-brain patient experiments.  Patients with severe epileptic seizures used to undergo a collosotomy, a procedure to cut the connections between the left and right hemispheres of their cerebrum.  It often helped alleviate their symptoms and, remarkably, the patients afterward remained mentally functional, at least to outside appearances.

Each hemisphere of the brain controls and receives sensory input from half the body.  What Perry and his colleagues discovered in their experiments, was that if sensory inputs going into the patient were isolated to one hemisphere or the other, each of the patient’s hemispheres were only aware of its own sensations, and with the language centers usually focused on the left hemisphere, the patient could usually only describe what they were seeing when the left hemisphere received it.

The fact that the patients, post-procedure, remained largely functional seemed to show that each hemisphere was effectively watching what the other half of the body did, and mentally confabulating the actions as its own.  It opened up the possibility that this happens even in healthy people, albeit to a lesser extent.

However, new research appears to show that this phenomenon may be more limited than previously thought:



A new research study contradicts the established view that so-called split-brain patients have a split consciousness. Instead, the researchers behind the study, led by UvA psychologist Yair Pinto, have found strong evidence showing that despite being characterised by little to no communication between the right and left brain hemispheres, split brain does not cause two independent conscious perceivers in one brain. Their results are published in the latest edition of the journal Brain.

Source: Split brain does not lead to split consciousness

Assuming there are not any methodological issues with these new experiments (always a possibility), and given everything I’ve learned about the brain since first reading about the split brain patient experiments, I can’t say I find this too surprising.

The corpus collosum connects the cerebral hemispheres of the brain, but there are other regions which connect the two sides of the brain, mostly sub-cortical.  These areas are generally below the level of consciousness, but the information from them feeds into the cerebrum.

These results are also consistent with the phenomenon of blindsight, where a patient that has sustained damage to visual processing centers in the occipital lobe (part of the cerebrum) cannot consciously see  something, but if pressed, can often still identify it.  The reason for this is that while the optic nerve does feed into the cerebrum, it also branches off to sub-cortical regions such as the superior colliculus in the mid-brain region.  Again, the processing in those regions is below the level of consciousness (at least in humans), but it provides information, to a limited degree, to conscious regions.

It seems likely that, for the patients in the lower row of the image above, something similar is taking place.  Each hemisphere may not be able to consciously perceive what the other hemisphere is seeing, but communication in sub-cortical regions is bubbling up into the cerebrum, enabling them to make the determinations that they’re making in the new experiments.  Maybe.

But I’m not sure this necessarily justifies saying that the patient retains one unified consciousness.  It may be that it is less divided than previously thought, but definitely is more separate than the consciousness of healthy people.  Of course, I’m basing these remarks on the press release.  The actual paper may shed additional light.

I definitely plan to watch for any new developments in this area.  Or for any comments from Michael Gazzaniga, one of Perry’s assistants who are still around and writing.

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Being a beast machine

In my post on consciousness possibly being a simulation engine, I noted Anil Seth’s excellent Aeon article as one of the inspirations.  As it turns out, Seth talked at a TEDx conference and covered many of the same topics he addressed in that article.

As noted in my post, I think a lot of what Seth describes here is actually unconscious perception.  If I’m right, it’s when those predictive models trigger multiple emotional reactions from our limbic system and we have to do simulations on various courses of action to decide what to do, that what we call consciousness actually comes into the picture.

I like one point Seth makes about proprioception.  He demonstrates, using the famous rubber hand test, that proprioception is a construction, a model created by the brain based on exteroception (sense of the outside world, including the external body), and interoception (sense of internal body states).  It’s become fashionable to tout proprioception and many other related perceptions as senses beyond the basic ones.  But if these additional perceptions are built on top of the basic ones, I think calling them senses in and of themselves is questionable.

Seth’s closing points about the self are worth pondering.  The self is a model, in many ways similar to the models we create for the external world.  As a result, that model can be different from the reality.  It can be wrong, no matter how privileged our access to it might feel.

Idealists ask whether the external world exists, whether or not we live in a simulation.  What isn’t often appreciated is that we definitely do live in a simulation.  Each and every one of us lives inside a simulation constructed inside our brain, both of the outside world and of ourselves.  As Seth says, “a fantasy that corresponds with the reality”, except that the reality is often a simplified cartoonish view of the reality, one adaptive for survival but not necessarily for giving us an accurate view of the actual reality.

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Two brain science podcasts worth checking out

As my long time readers will know, I’m very interested in the mind, and my preferred way to explore it is through science, notably neuroscience or cognitive psychology, or with science oriented philosophy.  With that in mind, I want to call your attention to a couple of podcasts I’ve been following for a while.

gingercampbellThe first is Dr. Ginger Campbell’s excellent Brain Science podcast.  The posting frequency isn’t very high, but most episodes are packed with interesting information.  The most common format is Campbell interviewing an author.  One of the recent episodes was an interview with Jon Mallatt, one of the authors of the book that has informed many of my recent posts on consciousness.  Older episodes feature neuroscientists whose work I’ve highlighted before, such as Michael Graziano and Michael Gazzaniga.

Some of the people and books that Campbell discusses do get pretty technical, but most of it seems oriented toward a science literate lay person.  Unfortunately, the older episodes are pay walled, but I’ve been impressed enough by the recent episodes to get a subscription to work my way through the archives.  I feel comfortable recommending this podcast for anyone with an interest in the brain and mind.

The other podcast is Brain Matters.  This is a much more hard core “inside baseball” show that often gets very technical, to the extent that I have trouble following many of the episodes.  It’s done by a group of neuroscience graduate students who most often are interviewing working neuroscientists.  As a result, the subjects can get somewhat arcane, with topics such as cortical columns, aphasia, mitochondria in neurons, or the tracing of particular neural circuits.  I don’t try to listen to every episode of this one, instead focusing on the ones where the title or description catch my interest.

Both of these podcasts can be subscribed to in the standard services.  (My subscriptions are through iTunes and the iOS Podcast app.)  Or they can just be listened to on their web sites.

If you know of any similar sources, I’d love to hear about them in the comments.

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America’s long path to universal voting rights

My memory of what I learned in early grade school about the history of American voting rights went something like this.  Prior to 1776, we were ruled by the king of Great Britain.  He was a tyrant who oppressed us with taxation without representation, so we rebelled and set up a democracy.  (UK readers, I see you rolling your eyes.)

There may have been a brief mention of slaves getting the vote after the Civil War (the slaves themselves weren’t mentioned until we got to the section on the causes of that war), but other than that, I came away with the impression that voting was mostly something we had figured out in 1776 with maybe some fine tuning in 1787.

Yep, the value of a public education.  To be fair to my state’s school system, the picture did get more sophisticated in middle school grades, but not by much.

Of course, the reality is that there had been elections in England for centuries before the American Revolution (which was a conflict against Parliament as much as with the king).  The American colonies had largely inherited the old English voting paradigm, which included allowing voting by males who owned a certain amount of property.  Many colonies also restricted the right to members of approved religious denominations.

The result was at the beginning of the United States, only a relatively small minority of the population could vote.  The exact percentage varied depending on locale, ranging from as low as 40% of adult white males to as high as 80%, depending on the availability and expense of property and the exact voting laws, with some estimates of the overall percentage of the American population that could vote being as low as 6%.

The progress from that initial very limited suffrage to the near universal suffrage we have today happened in what I would call four waves.  The first wave enfranchised most white males, the second wave briefly enfranchised blacks, the third wave women, and the fourth re-enfranchised blacks along with much of the remaining excluded population.

The first wave happened in the early 19th century.  White males who didn’t have the vote were pushing for it, but that by itself wasn’t enough to make it happen.  There was a strong sentiment that only those with a stake in the society should be allowed to vote, as well as a concern that too broad a franchise might allow elections to be swayed by a nascent working class enslaved to their employer’s interests.  Many fretted that America might someday become a country of working class people instead of farmers.

Proponents of broader suffrage argued that fears of a working class country were unfounded, that America would always be predominantly agrarian.  The proponents had to be careful in the arguments they used, focusing on why their particular group should have the vote without implying that voting was any kind of general right.  Such a right might imply that women, blacks, and natives should be allowed to vote, which everyone regarded as crazy talk.

The success of this wave came from a number of factors.  The rise of national political parties played a role, allowing voters who had the right to vote in one type of election to punish a party that opposed their right to vote in other elections.  In addition, the War of 1812 shed light on the fact that soldiers without the right to vote had a lower incentive to fight.  But perhaps the largest factor may have been new states in the west, who used broad white male suffrage to attract migrants, which put competitive pressure on the eastern states to expand their own franchise.

The result was that by more or less 1850, if you were male, white, and paid taxes (the standard that replaced the property requirements), you probably could vote.  Still excluded at this point were women, blacks, most native Americans, paupers, and most immigrants.  The first half of the 19th century was a period of mostly optimism about democratic ideals.

The second half wouldn’t be.  As America indeed started to become the working class society people of a previous generation had feared, those fears came roaring back, leading to widespread nativism and discrimination.  When we think of the later 19th century, we often might think of the Civil War and Reconstruction, of blacks getting the right to vote.  This was the second wave I mentioned above.  But it happened in an era of otherwise rising skepticism about the ideals of a broad democracy, which is likely why the second wave mostly floundered.

As Reconstruction ended and white southerners seized back control of their states, the north showed little interest in stopping the subsequent large scale disenfranchisement of blacks.  Yes, the 15th Amendment was on the books, theoretically guaranteeing blacks the right to vote, but after the first decade or so of its ratification, only the most brazen violations of it were policed, generally allowing Jim Crow era laws to develop.  It was a stark demonstration that liberal laws are impotent if the people in power won’t enforce them.

The late 19th century turn against democracy also resulted in strong headwinds for the women’s suffrage movement, which is usually considered to have started in 1848.  Those headwinds resulted in little progress before 1900, although women did often get the right to vote in some local elections such as for school board positions, and a more broad right in a few western states.

The third wave for women’s suffrage didn’t really heat up until the early 20th century, when women’s groups became far more organized and aggressive.  In addition, the industrial nature of World War I demonstrated that women could contribute substantially to war efforts, something that had been a convincing argument in the first two waves.  That and there was an international movement in several democratic countries to enfranchise women.  All of which culminated in the 19th Amendment being ratified in 1920.  (Interestingly, this was followed by a very conservative decade in American politics.)

The Great Depression in the 1930s led to something of an ad-hoc change.  Paupers continued to be largely excluded from the voting franchise, with technically anyone receiving any kind of welfare considered a pauper.  However, the large scale unemployment and hardship of the 1930s made officials reluctant to label anyone on relief a pauper, which largely ended that exclusion.  It became kind of an inversion of the situation with the 15th Amendment.

The fourth wave started with World War II.  Part of the war propaganda on the western side focused on the fact that we were democracies and the enemies weren’t.  (I guess conveniently ignoring the realities in Russia.)  That and the fact that the Nazis saw American racial laws as a source of inspiration for their own policies, policies which resulted in the Holocaust.  This seemed to turn a harsh light on the differences between the ideals of American democracy and the reality.  It was also recognized that America’s racial issues gave the communists a Cold War propaganda issue.

Nevertheless, the fourth wave was a long slog, starting with desegregation of army barracks in the late 1940s, and civil resistance from blacks themselves in the 1950s.  Eventually the result was the Civil Rights Era.  This resulted in laws passed in the 1960s guaranteeing blacks the right to vote, finally fulfilling the promise of the 15th Amendment a century after it has been ratified.

But the Civil Rights Era also included a rush to correct other longstanding issues with American voting, so that many groups that had been excluded by a variety of underhanded techniques, such as American Indians, mobile workers, recent immigrants, paupers, and other smaller groups were finally enfranchised.  It was a period when the Federal government finally took an active role in ensuring the right to vote.  By the early 1970s, America finally had near universal suffrage.  (“Near” because in many states convicted felons, insane people, and other similar categories continue to be excluded.)

When I was younger, I never realized just how recent this development had been.  Nor how fragile or incomplete it was until the 2000 election with all the disputes about voting laws and the electoral college, or again when in recent years the Supreme Court invalidated substantial portions of the Voting Rights Act of 1965, not to mention the election we just had.

As always, I find reading history helps to put our own times in context, which can be comforting in some ways but alarming in others.  Reading about voting rights history in America shows that voter eligibility has always been a partisan issue, and that the times we live in aren’t nearly as uniquely blinkered as we might fear.  On the other hand, it also shows that our conception of democracy is a very recent one, and that there’s no guarantee that past progress can’t be reversed.  Vigilance is always required.

therighttovotecoverMuch of the information in this post came from ‘The Right to Vote: The Contested History of Democracy in the United States‘ by Alexander Keyssar.  I can’t say this was an exciting read, and the Kindle version had some unacceptable formatting issues, but I found it a fascinating source of information for this topic.

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Merry Christmas

Real Clear Science highlighted an interesting article from a few years ago on the evolution of Santa Claus: Will the Real Santa Claus Please Stand Up?

We always think of Santa Claus as an incredibly old man—positively ancient—but the fact is, he’s exactly 150-years-old, born in 1863. Indeed, we might be thinking of Santa’s predecessor St. Nicholas, who is far older, believed to have been a Turkish Greek bishop in the 300s. But the first European winter gift-bringer is even more of a geezer, going back to ancient Germanic paganism and the Norse god Odin. When he wandered the earth, the deity disguised himself as a bearded old man wearing a broad-brimmed hat and cloak and carrying a traveler’s staff. He looked a lot like Gandalf the Gray in “Lord of the Rings.”

The gift-bringer showed up during the 12-day winter festival known as Yule, where it was a tradition to burn a whole tree, from bottom up. (This evolved into the smaller “Yule log” we know today.) Children would leave hay in their shoes for Odin’s eight-legged horse and find it replaced with treats the next day. As Europe became Christianized, these beliefs were absorbed into the Christian faith, and St. Nicholas, celebrated on December 6, was bestowed with the gift-bringer mythology.

And related to Odin’s eight-legged horse:

via xkcd

Whatever this weekend means for you, I hope you and those you care for are safe and having a Happy Holiday, free of eight legged horses.  (Unless of course an eight legged horse is what you want for Christmas.)

Merry Christmas to all my online friends!

Posted in Zeitgeist | 20 Comments

A possible answer to the hard problem of consciousness: subjective experience is communication

In 1995, David Chalmers coined the “hard problem of consciousness”:

It is undeniable that some organisms are subjects of experience. But the question of how it is that these systems are subjects of experience is perplexing. Why is it that when our cognitive systems engage in visual and auditory information-processing, we have visual or auditory experience: the quality of deep blue, the sensation of middle C? How can we explain why there is something it is like to entertain a mental image, or to experience an emotion? It is widely agreed that experience arises from a physical basis, but we have no good explanation of why and how it so arises. Why should physical processing give rise to a rich inner life at all? It seems objectively unreasonable that it should, and yet it does.

…The really hard problem of consciousness is the problem of experience. When we think and perceive there is a whir of information processing, but there is also a subjective aspect.

Chalmers was giving a label to an issue that has existed for a long time, but his labeling of it has given many a clarity on why they find many scientific explanations of how the brain and mind work to be unsatisfactory.  Bring up the scientific understanding of consciousness, and someone is going to ask why all the data processing is accompanied by experience.

My last post discussed a movement in the philosophy of mind to label this distinction as an illusion.  And to be clear, I do think the idea that experience is something separate and apart from the information processing of the brain is an illusion.  That’s not to say that I think subjective experience itself doesn’t exist in some form.

But that still leaves the question of why we have subjective experience.  In earlier posts, I’ve noted that to have any hope of answering that question, we have to be willing to ask what experience actually is, and gave my answer that it is a system building and using internal models of the environment and of itself, in essence an inner world, as a guide to action.

I still think this answer is true, but in conversation with fellow blogger Michael, I realized that there may be a better way of articulating it, one that may resonate a little better with those troubled by the hard problem, at least with those open to explanations other than substance dualism or speculative exotic physics.

I think subjective experience is communication.

Consider that every aspect of experience seems to have a communicative value.  Using the examples Chalmers gave in the quote above, the deep blue communicates information about the object being modeled such as maybe a deep lake, and the sensation  of middle C communicates something about the environment (or given the nature of music, or art in general, the illusion of something).

Other examples are the vividness of red communicating ripe fruit, pain communicating damage to the body, severe pain communicating damage serious enough to perhaps warrant hiding and healing, or the delight of a child’s laughter communicating that the next generation of our genetic legacy is happy and healthy.

Now, the question you’re probably asking is, communication from what to what?  I think the answer is communication from various functional areas of the brain to the movement planning areas.  The source areas include the sensory processing regions, which model the information coming in from the outside world, and the limbic system, which adds valences to the models, that is judgments of preference or aversion.


Image credit: Anatomist90 via Wikipedia

The Limbic System: Image credit: OpenStax College via Wikipedia

The Limbic System: Image credit: OpenStax College via Wikipedia

(For those familiar with neuroanatomy, by movement planning areas I mean the prefrontal cortex, by sensory processing areas I mean the middle parietal lobe, posterior cingulate cortex, and all the regions that feed into them, and by limbic system I mean the structures commonly identified with that term, such as the amgydala, anterior cingulate cortex, hypothalmus, etc.)

Of course, as I noted in the post on consciousness being predictive simulations, this is actually a two way communication, because those movement planning regions instigate simulations that require participation of all the source regions.  But what we call experience itself, may be the preparation and transmission of that information to the executive centers of the brain, executive centers whose job it is to fulfill the main evolutionary purpose of brains, to plan and initiate movement.

One quick clarification.  This isn’t an argument for a homunculus existing in those executive centers.  This isn’t the Cartesian theater.  It’s communication from the sensing and emotion subsystems of you to the action oriented subsystem of you, and consciousness involves all the interactions between them.

Now, it’s almost certainly possible to find aspects of experience that science doesn’t have a communicative explanation for yet.  But is it possible to find any for which there is no conceivable explanation?  Even if there is, even if we can find the odd part here or there that has no imaginable explanation, if we can find ones for the vast majority of qualia, doesn’t that mean that most of them are fulfilling a communicative function?  And that experience overall is generally about communication?

Indeed, if you think about it, isn’t this type of communication crucial for a brain’s evolutionary purpose?  How else can the movement planning portions of the brain fulfill their function other than by receiving information from the input processing and evaluative portions?

If so, for a philosophical zombie to exist, it would need to have an alternate mechanism for this communication.  But why wouldn’t that alternate mechanism not simply be an alternate implementation of subjective experience?  If this view is correct, zombies are impossible, at least zombies sophisticated enough to reproduce the behavior of a conscious being in a sustainable manner.

So, this seems to be a plausible explanation for what experience is, and why it exists.  It seems like a possible answer to Chalmers’ hard problem.

Unless of course, I’m missing something?  In particular, what aspects of subjective experience might not fit this conception of it?  Are they significant enough to discount the answer?  Or are there other problems I’m not seeing?

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The illusion of phenomenal consciousness?

Keith Frankish

Keith Frankish, the main proponent of illusionism in the JCS issue.

Philosopher Peter Hankins at Conscious Entities has a write-up on the November 12 issue of the JCS (Journal of Consciousness Studies) in which philosophers, psychologists, and neuroscientists such as Keith Frankish, Daniel Dennett, Susan Blackmore, and Michael Graziano, debate whether it makes sense to refer to phenomenal consciousness as an illusion.  Unfortunately the full text of the journal articles are paywalled, although if you are on a university network, or have the ability to access the site through one, you might find you can reach them.

Saying that phenomenal consciousness is an illusion is often met with derision.  The phrase “is an illusion” is meant to state that consciousness isn’t what it appears to be, but many people read it as “does not exist”, which seems self evidently ludicrous.  Which is why, while I generally agree with the illusionists ontologically, that is with their actual conclusions about reality, I’ve resisted using the “illusion” label for the last few years.  As one of the JCS authors (Nicholas Humphrey) stated, it’s bad politics.  People have a tendency to stop listening when they perceive you’re saying consciousness isn’t there.

And it can be argued that, whatever phenomenal experience is, we most definitely have it.  And that the perception of a subjective experience is the experience, such that questioning it is incoherent.  I have some sympathy with that position.

But as I commented on Peter’s post, after perusing many of the papers, I’m starting to come back around to the position I held when I first started this blog.  Conscious experience isn’t what it seems to be.  That’s not really a controversial statement to most neuroscientists or other cognitive scientists.  Maybe “illusion” is the right description.

The hard problem of consciousness is based largely on the observation that conscious experience is not subjectively reducible.  Because of that, from the subjective point of view, it seems inconceivable that physical matter could give rise to that subjective experience.  I’ve noted before that I think the answer is to ask what experience actually is.  But that inherently implies that it is not the irreducible fundamental aspect of reality it appears to be.

Saying that phenomenal consciousness is an illusion is provocative, edgy, and forceful.  As a statement, it requires further explanation.  But it also clearly communicates the basic point, that conscious experience, phenomenal experience, qualia, are not what they seem to be.  That introspection is not a reliable source of information.

It also changes the hard problem from the question of why we have irreducible  experience as we perceive it, to why we think we have it.  To be sure, this new problem is far from easy to solve, but it doesn’t seem to have the intractability of the original one, and I’ve already given potential answers to it in previous posts.

Just to be clear, no one really doubts the information processing aspects of consciousness, sometimes called access consciousness.  The question is whether there is really a distinction between access consciousness and phenomenal consciousness, the raw feeling of experience, the painfulness of pain, the redness of red, etc.  Subjectively there certainly feels like a distinction.

But we have no good reason to think that raw feelings are themselves anything other than information.  Pain is a signal that electrochemically traverses neurons and synapses from the effected body part to the brain, where key regions such as the anterior cingulate cortex interpret it as pain.  These are the information processing aspects of it.  The idea that this is separate from the feeling aspect is part of the illusion.

This isn’t to say that the illusion is a mistake we somehow make.   On the contrary, it appears to be an important evolutionary adaptation.  There’s no particular survival advantage to our introspective models giving us a rigorously accurate picture of the internals of our mind.  Instead, it gives us a simplified picture that is effective for survival.

Nor is it to deny the breadth, richness, and depth of human experience, or its intensity, or any of the things that come with it.  All that’s being stated is that the experience, for purposes of understanding the workings of the mind, shouldn’t be taken at face value.

So, by calling phenomenal consciousness an illusion, we quickly communicate that subjective experience is not what it appears to be, that introspection is not to be trusted, that the hard problem is itself an illusion, and perhaps focus scientific efforts more productively.  What’s not to like?

Yep.  Something tells me that this issue of the JCS will generate a lot of responses throughout the philosophy of mind and perhaps other cognitive fields, and that this is a question that will be revisited a lot in the future.

What do you think?  Is the illusion label going too far?  Does it, as Philip Goff, one of the critics in the JCS issue, simply show that people like me are “in the grip of scientism”?  Or are there other downsides that I’m missing?

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