Controllers?In my brain?

I have been hearing a lot of buzz lately about Asim Roy’s newly published paper Connectionism, controllers, and a brain theory. What is all the hype about? Well, Roy claims to be offering a “new theory for the internal mechanisms of the brain.” Sounds exciting doesn’t it? What could Roy be proposing that is so revolutionary? Roy proposes that…wait for it… some parts of the brain control other parts! I suppose most of you aren’t exactly blown away, and I certainly wasn’t either.

Roy’s rhetoric is obviously pretty overblown, but let us give him the benefit of the doubt and move on to his actual arguments. He starts off by claiming that connectionist theory “postulates that the brain does not have controllers in it.” He quotes Rumelhart, Hinton, and McClelland as saying “there is no central executive overseeing the general flow of processing.” Seems pretty non-controversial to me though. They seem to be merely saying that there isn’t a homunculus in the system, controlling everything with a immutable Will. Philosophy 101. So what is Roy actually arguing against? A straw man? Sort of, but not quite. Roy argues that in connectionist models, there is a “controller” in the system that controls the learning algorithms and thus connectionist theories are essentially rooted in control-theoretic modeling.

But, as peter over at conscious entities mentioned, connectionist theorists haven’t exactly gotten to the point where they are proposing a general architectural model of how the brain works. It seems entirely plausible that when connectionist models get to that point of complexity, they wouldn’t hesitate to propose that some modules control other modules. Otherwise, I don’t see how one could get a theory that modeled high-level cognition. The way Roy structured his arguments, I don’t think anyone would argue against the idea that “there are parts of the brain that control other parts.” Furthermore, Roy himself undermines his claim for proposing a “new paradigm” when he says things as trivially obvious as:

It should be pointed out that this theory does not posit that there is a single executive controller in the brain. [b]Instead it envisions “multiple distributed controllers” controlling various subsystems or modules of the brain[/b]. The main argument of the paper that connectionists use “executive controllers” is only pointing out that their algorithms use a “central controller.” But different modules in the brain using connectionist-type learning can have their separate controllers.

I’d also like to point out that Roy was beaten by at least ten years on his emphasis of controllers. In his 1997 book Being There, Andy Clark says:

The idea here is that the brain should not be seen as primarily a locus of inner descriptions of external states of affairs; rather, it should be seen as a locus of inner structures that act as operators upon the world via their role in determining actions…This perspective leads to a rather profound shift in how we think about mind and cognition-a shift I characterize as the transition from models of representation as mirroring or encoding to models of representation as control

So contrary to Roy’s strong rhetoric, people sympathetic to connectionist theory such as Clark have been thinking about the mind and the brain in terms of action-oriented controllers for many years. In conclusion, I agree with Roy’s essential argument that there are parts of the brain that control other parts of the brain, but I don’t think this is a revolutionary of a paradigm as he thinks it is. Roy himself quotes from all over the neuroscience literature showing that it is riddled with control-theoretic terms, and by his own argument, he shows that connectionist theory is also already steeped in control theory. Surely, the connectionists themselves understand this. So who is Roy arguing against here?

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Tool Use: Part of the Body Schema

The Italian Neuroscience Mafia is at it again: Giacomo Rizzolatti and cohorts recorded the brain activity of macaque monkeys in the F5 and F1 areas while they were grasping with their hands and then when they were grasping with a pair of pliers. Remarkably, the same neurons fired in the same order when they were grasping with their hands as when they were grasping with the tool. Furthermore, the same neurons also fired in the same order when the monkeys used “reverse pliers” that required closing and then opening the hand in order to grasp the food. Because of this, the researchers concluded that “the capacity to use tools is based on an inherently goal-centered functional organization of primate cortical motor areas.”

Their evidence clearly shows that there are cortical neurons in the F5 and F1 area that code for for the goal of motor acts, instead of the motor act itself. These neurons are then connected to neurons that more specifically code for the motor act of opening and closing. Furthermore, the researchers show evidence that amidst the goal-directed neurons in the F5 area, mirror neurons are also involved, which code for goal-directed actions during the observation and execution of an act and are rich in the F5 area.

Monkey Thoughts >> Robot Action

I think it is interesting that at the end of the video, the researcher says “the brain was freed from the body and could act upon the world directly”. This seems like a strange thing to say. Isn’t using your body a direct way of interacting with the environment? How is controlling your body any different from controlling a robot arm? Isn’t the result(that you are acting in an environment) the same regardless?

Check out this NY Times article on the same researcher:
Monkey’s Thoughts Propel Robot, a Step That May Help Humans

“Unconscious perception” and the body schema

In this post over at Science and Consciousness Review, Stan Franklin discusses how the dorsal, or “where” stream of visual perception is unconsciousness. In contrast to the ventral stream, which is responsible for the “what”, or object recognition, the dorsal stream is involved with spatial awareness for actions such as grasping.

Franklin cites work from Goodale and Milner that studied a patient with an impaired dorsal stream. After careful experimentation, Goodale and Milner concluded that the dorsal stream is unconscious. Normally, I do not like discussing perception in terms of the conscious/unconscious dichotomy, but I though this conclusion was interesting because of its implications for Shaun Gallagher’s preconscious body schema, that I discussed in this previous post. This body schema is a system of sensory-motor capacities that is responsible for such pre-reflective activities as walking, keeping upright posture, and other motor actions that we do more or less “unconsciously” such as appropriately  molding our grip to reach an object. So, with respect with the unconscious dorsal processing Franklin was discussing, I think the body schema is an appropriate theoretical construction that fits the evidence.

Consciousness and sleep

In this post, I want to discuss a paper entitled the “Breakdown of Cortical Effective Connectivity During Sleep”. In plain English, this paper discusses the theoretical possibility that consciousness fades during the night because the cortex essentially doesn’t talk to itself as much. More specifically, this study focused on NREM sleep, which accounts for roughly 75-80% of our total sleep time. During NREM sleep, people often report no dream experiences, and it is this lack conscious activity that the researchers wanted to investigate. What goes on in our brains during this period of non-consciousness?

In order to answer this question, the researchers used a combination of transcranial magnetic stimulation(TMS) and electroencephalography(EEG). Using TMS was advantageous for the researchers because they could stimulate the cortex directly without activating the subcortical reticular formation and the thalamo gating relay.

The researchers used TMS to stimulate the rostral portion of the right premotor cortex, which has dense connections with the rest of the cortex area, which is heavily correlated to typical wakeful consciousness. Now for the results:

During wakefulness, TMS induced a sustained response made of recurrent waves of activity…With the onset of NREM sleep, the brain response to TMS changed markedly. After [the initial] large wave, no further TMS-locked activity could be detected.
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Thus, during wakefulness, the perturbation of the rostral premotor cortex was followed by spatially and temporally differentiated patterns of activation that appeared to propagate along its anatomical connections. In striking contrast, during NREM sleep the location of maximum current density remained confined to the stimulated area.
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During wakefulness, the site of maximum activation moved back and forth among premotor and prefrontal areas in both hemispheres and, in some subjects, it also involved the motor and posterior parietal cortex. During NREM sleep, by contrast, the activity evoked by TMS did not propagate in space and time in any of the subjects.
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Thus, an impairment in the ability to integrate information among specialized thalamocortical modules—a proposed theoretical requirement for consciousness—may underlie the fading of consciousness in NREM sleep early in the night.

The researcher’s speculation on the potential neural mechanisms behind this decreased cortical activity during NREM sleep is a little beyond the scope of this blog, but it could have something to do with “down states” of depolarization being triggered more easily. Regardless,

Whatever the precise mechanisms, they are most likely engaged by the progressive reduction of the firing of diffuse neuromodulatory systems that occurs when we fall asleep.

For those interested, a good summary article of this research can be found here

Thoughts on perception

This is a painting done by a congenitally blind artist named Esref Armagan.

The most obvious question is how his brain is able to perform such feats of perspective, but as the article mentions, it is well understood that “blind people… understand and can draw in three dimensions”

With that said, I think this particular “how” question is easily answered with modern paradigms of neural plasticity/pruning etc

I believe the more puzzling question to ask is not how he can perform such tasks, but rather, how his developing brain learned to generate high-order representations of three-dimensional space to such a phenomenal degree of accuracy.

Well, “I was taught, he says. Not by any formal teacher, but by casual comments by friends and acquaintances.”

This remark, combined with the fact that “it is impossible to know if he had some vision as an infant”, makes it difficult to extract any conclusive insights about whether his “mind’s eye” is purely mapped out in non-visual sensory-terms (the primary contributors likely being kinesthetic and proprioceptive), and his incredible “accuracy” is simply the result of his early peers subtlety nudging him back and forth until he got it “right”.

An alternative answer is that his brain got some “extra” reinforcement by crude visual data before his eye completely degenerated, thus making his inner conceptual space not in purely non- visual terms as is suggested by the article. This would also explain why his degree of accuracy is greater than most other congenitally blind people.

These are difficult, but fascinating problems in the psychology of perception, but regardless of Mr. Armagan’s unique skills, there seems to be an emerging consensus from all psychological disciplines that whatever “perception” is, it is realizable across many different modalities.