The authors propose that consciousness may be associated, not with activation in any given area of the brain, but with recurrent information processing between areas, a kind of neural ping-pong.
When presented with sensory information, say the sight of an object, signals travel up through the brain from "primary" sensory areas to "higher" areas associated with more complicated processing. They call this the Fast Feedforward Sweep, or "FFS". Maybe not the best acronym.
Anyway, depending on the nature of the stimulus, this can lead to activation in almost any part of the brain. However, they say that it's not enough to generate consciousness; only if the later areas feedback to the earlier areas, and start a recurrent processing loop, does this happen.
This stands in contrast to the popular view, which seems to fit with common sense, that primary areas are unconscious and that consciousness is directly associated with activity in the higher areas, in particular, the prefrontal cortex (PFC).
The authors refer to fMRI and EEG studies showing that even "high level" processes, such as selective attention to stimuli, and inhibition of an action, can be triggered by subconscious cues, and that this is associated with activation in the prefrontal cortex - unconscious activation.
The details of these studies are fairly arcane but the point is that the prefrontal cortex is generally agreed to be the most developed, "highest level" part of the brain. If anywhere in the brain was going to be the seat of the soul, it's the PFC.
This shouldn't come as a surprise, though. While it's tempting to look for a part of the brain which "does" conscious experience - the "me module" - Daniel Dennet pointed out a while ago that this temptation is motivated by a fundamental confusion.
Likewise, while it seems common sense that conciousness is the "highest mental function" and therefore must be located in the highest brain area, this is a presumption: consciousness is a mystery, and we don't know if it's a high level function or not, or whether that question even makes sense.
Nor should the fact that consciousness isn't an inevitable consequence of high-level cognition come as a shock: in fact, that would be impossible. As Ryle pointed out in The Concept of Mind, this would create an infinite regression. Any conscious experience has to come from somewhere.
Right now I'm concious of choosing certain words rather than others in typing this post, in a conscious attempt to make it read better. But I'm not aware of all of the rules and experiences that guide my choices. I just feel that some words work. This feeling seems to come out of nowhere, or rather, out of the words themselves.
It isn't, of course, it's a product of calculations taking place in my brain, but I've no idea what they are. I wouldn't want to be, either: I'm too busy typing.
van Gaal S, & Lamme VA (2011). Unconscious High-Level Information Processing: Implication for Neurobiological Theories of Consciousness. The Neuroscientist : a review journal bringing neurobiology, neurology and psychiatry PMID: 21628675
13 comments:
I fail to see how it could be anything else. There is nowhere near enough processing power to consciously process everything real-time. It has to be subdivided and later collated.
Glad someone finally got on track.
Just a little correction -- you typed "Rawls" for *Concept of Mind*; should be "Ryle" (BTW: great blog)
Thanks for the tip-off. My conscious mind knew who I was referring to but my typing module got a bit confused.
No Neuro, you just made a Freudian slip.
What did they do in this study? Record activity in the brains of people who were doing a Go/NoGo task with some of the images being masked so as to restrict conscious perception of target images? Did they measure reaction times? It isn't clear what was done from the abstract, and I only gathered some information from the caption you included.
I just saw Integration Without Awareness
Expanding the Limits of Unconscious Processing and it looked interesting enough that I paid for access. I am still reading it, but it seems to have a similar type of task, except their task seems more cognitively complex with respect to what they show as a stimulus.
(and in that paper, their technique for masking a visual stimulus was to use "continuous flash suppression".)
If it were a Freudian slip that would mean I really wanted to write a post about John Rawls. But I don't like Rawls and I don't not like him enough to want to criticize him.
Unless I have some subconcious attraction to massive glasses.
So interesting that people want to seat consciousness in the PFC. Understandable. However, you yourself noted that feelings were directing which words you chose whilst writing this article.
The popular TNG character "Data" is a sentient being without an emotion chip. It is an assumption that sentience could exist in this form at all. That we find "Data" a compelling character at all may point to the underlying myopia to just how feeling driving even the most logic mind is.
I suspect that consciousness is generated my more primitive parts of the brain, which commandeer the PFC to handle calculations and test propositions.
Great post.
It's worth mentioning that Lamme is trying to promote his recurrent processing theory/model for quite some time now (I think the first paper came out around 2002).
The main proponent is actually Stas Dehaene's theory of global workspace. They've been bashing for a couple of years now.
It is interesting to mention that such studies may have enormous clinical consequences for patients "without" conscious awareness (eg. in vegetative state). How do we determine whether the patient is truly unaware?
I recommend reading this article: http://www.sciencedirect.com/science/article/pii/S1364661305002998 , it's very short and has interesting references.
Laureys points out that activation in sensory cortices (following for example pain) is present in vegetative patients, but this activation is functionally disconnected from higher order areas.
You missed the point Neuro: Rawls "ryles" you which is why you made the Freudian slip.
I'm no neuroscientist, but I'm surprised that anyone would look for a "seat of consciousness" smaller than the brain itself. In fact I would have thought that the whole organism is involved - after all we also have 100 million neurons in our gut for instance.
The brain is not an isolated system. It can't survive, let alone function, on it's own. It is a network of networks - and sits at the centre of a complex nervous system that extends through the whole body. All embedded in an organism made up of cells that not only do their own thing, but also coordinate themselves outside of the nervous system (and cells are not simple by any means!). The symmetry is fractal and we see evidence of organisation at whatever level we examine the system. But a vocationally based preference for examination on a single level does not equate to the whole picture no matter how attractive it seems. Yet we often find researchers confidently "locating" consciousness at the level of their specialist area of investigation.
A Freudian slit usually involves an unconscious emotion, which by definition we are not aware of. It can take quite a lot of analysis to uncover the source. Who knows what the author was thinking, and with which part of his brain?
BTW That was a deliferate mistale. ;-)
As a concious entity myself, I know that I am concious because I can feel it. I have no proof that you or anyone else is really concious. I know that you are intelligent beings. There is no reason to assume that because a being is intelligent that it is also concious. Computer algorithams will be more intelligent than us one day.
Conciousness cannot be observed. I believe this is because when it is observed it is destroyed, just like physical objects that are in an undetermined quantum state. It now appears that quantum physics is no longer a science about the extremely small, it is now a science that affects every part of the physical universe, every cell in the human body and requires a brigding of very different sciences before we can begin to comprehend its relation to conciousness.
Great post; it highlights the shift from localisatist to more dynamic views of consciousness. Feedback theories of consciousness are currently divided over one major question; what forms of feedback are related to consciousness? On the one hand, Lamme has typically argued that any form of reiterant processing between two brain regions qualifies as consciousness. For example, conscious perception of motion comes from reiterant processing between primary visual cortex (V1) and motion selective cortex (MT) whereas conscious perception of colour comes from reiterant processing between V1 and colour selective cortex (V4). On the other hand, Dehaene’s theory proposes that consciousness is related to widespread reverberant activity between frontal and parietal brain regions with perceptual brain regions. The important difference here is that Lamme (along with Christof Koch and Ned Block) proposes that there can be non-cognitive forms of consciousness (e.g., phenomenology) that arise from local reiterant processing whereas Dehaene argues that consciousness is restricted to only large scale cognitive processes related to global reiterant processing.
Post a Comment