I’ve posted on HOT (higher order thought theories of consciousness) before, but there’s a new paper out covering the basics of these types of theories. Since first reading about HOT many months ago, the framework has been growing on me. The paper is not too technical and I think would be accessible to most interested readers.
In general, HOT is the idea that first order representations, the sensory images formed in early sensory areas of the brain, such as in the visual cortex, are not by themselves sufficient for being conscious of their contents. We can hold and react to such representations unconsciously.
In order to be conscious of the representation, a second or higher order representation is needed, a representation about the first representation. Inner awareness comes from these higher order representations accessing the first order representations.
Under most HOT theories, the higher order representations are in the prefrontal cortex. This puts the PFC at the center of consciousness, a contentious view. Although there is an openness to the possibility that some higher order representations might be in the parietal or temporal lobes.
I was a bit surprised that the paper described GWT (global workspace theory) as a first order theory. GWT posits that for a perception to enter consciousness, it must be broadcast into the global workspace. I would have thought that GWT was agnostic about how the information from the representation made it to the various cognitive modules.
I envisioned that GWT might provide a big picture view of what was happening, with HOT providing the details, and each of the cognitive modules holding their own versions of the representation, that is, their own representation of the initial one, tailored to their own needs. But apparently GWT is more specific in its views about how the information is broadcast and received. If so, that threatens to weaken GWT in my eyes, making it into a sort of data bus that I’m not sure matches the actual biology.
One of the things I do wonder about HOT is how accurate it is to call the higher order representations… representations. It doesn’t seem controversial to say there is processing happening in other regions that make use of the information from the first order representations, or that being conscious of the representations requires processing outside of them. But saying the information held by this other processing itself amounts to a representation might be an oversimplification.
Indeed, the division that many of these theories make between the representations and the processing that happens about the representations has long struck me as artificial. I suspect there isn’t any clean line. The representation probably gradually morphs through processing layers to being processing about associations of the representation and other related information.
Still, HOT strikes me as a productive way to think about inner experience. We just have to remember that the higher order representations are not just mirror images of the first order ones, but are heavily tailored to the needs of the regions in which they exist. Representations in the prefrontal cortex are likely integral components of action plans.
Interestingly, reading this paper, I realized that another theory I’ve long been fond of, Michael Graziano’s AST (attention schema theory), is itself a type of higher order theory, although I haven’t seen it described anywhere as one. AST posits that the brain holds a representation, a schema of the process of attention, and that inner awareness results from this representation.
Graziano doesn’t see the schema as being in the prefrontal cortex, but in regions along the border between the parietal and temporal lobes, although the prefrontal cortex may be involved. And again, various HOT theories seem open to the possibility of some higher order representations being outside of the prefrontal cortex.
HOT theories are almost certainly not the final word, if for no other reason than they differ on various points, and I suspect the devil is in those details, but the overall viewpoint strikes me as having promise.
Unless of course, I’m missing something?
11 thoughts on “Higher order theories of consciousness”
When I consider how memories are stored in pieces and reassembled when “accessed” it seems reasonable that the “higher order” use of images and whatnot would not contain such a representation, but would contain a connection to it. The current explorations of information surging around the brain makes this a somewhat likely scenario. So, consciousness is another layer of access, if you will, to the contents of the brain’s storage. Of course, it must be a separate system of access but at least there is already such a system being modeled (memory).
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That’s my concern with the “representation” label. I sometimes wonder if they wouldn’t be better off with just calling it a “concept”, or maybe an “association”. Their point might be that the prefrontal cortex has access to all the details of the representation, and that having that locally might be a benefit. And it might. But I don’t know if that’s necessarily the way the brain does things.
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That’s why I found the reconstruction of memories to be telling. the visual parts are stored over there, the aural parts, over there, the emotional parts, in that part of the brain, etc. So, the singular memory (or so it appears to us) is actually a composite. And the “memory” master file can be rather small as it doesn’t have to include all of the data, just synaptic links to in, along with a reconstruction plan. Actually, a reconstruction plan may not be necessary. Playing a visual file and an audio file simultaneously may result in them being synchronized automatically. How the brain does these things, I do not know, but apparently this is how memories are “stored” and “recalled.”
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I think the right way to think of an episodic memory is as a reconstruction, a simulation of a past event built with individual semantic memories. It’s why human memory is so unreliable. Foresight and hindsight seem to use the same neural machinery.
I had a very similar reaction. I’m only halfway through the paper, but it’s clear that some of the “HOT” theories don’t posit higher order representations. So I think “Higher Order Processing” would be a better label, if one wants to include all those theories.
It sounds to me like HOT is modeling consciousness according to hierarchical databases, but these kinds of databases tend to have rather rigid schemas. I would rather use networked databases to model consciousness, with more ad hoc schemas offering more flexibility to fit the needs of an adaptive consciousness. Part of the conceptual network might be flat while other parts might be hierarchical. If I’m not mistaken, this is kind of how neural computing works.
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I don’t think there’s necessarily anything in HOT that requires a hierarchical structure, although I do think of a first order representation as a number of attribute hierarchies that bleed over into each other.
But you raise a good point. It might not be one structure in the prefrontal cortex that models an early sensory representation, but several, each with it own needs and concerns. HOT seems to imply that it would all be concentrated in one higher order representation, but I’m not sure that’s necessary. And it may be that the specific theories don’t stipulate that.
I come back to wondering how different the higher order representations need to be before the word “representation” is no longer productive.
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