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Alva Noe’s Philosophical Concepts 4: Neural Plasticity

Written by Jeff Drake
10 · 27 · 19

Here, Professor Noe takes us into a deep dive of something called “neural plasticity.” This post continues the discussion I began in “Alva Noe’s Philosophical Concepts 3.” I do recommend that you read this series of posts in order, beginning with 1, to get the most out of it.

The following discussion is based on information that can be found fully described in Alva Noe’s book, Out of Our Heads: Why You Are Not Your Brain and Other Lessons from the Biology of Consciousness. I urge you to read it.

I had stated at the end of Alva Noe’s Philosophical Concepts 3 that I would discuss the problem of “other minds.” However, I have decided to forego this particular discussion as it is a debate that in many cases is only of interest to philosophers. The majority of us, I strongly suspect, don’t worry about whether or not other people really exist or are possible figments of our imagination. If anyone feels compelled to argue this point, please talk to me offline, or better yet, don’t What would be the point? ?

Instead, I want to move into a more interesting area of discussion and talk about something scientists call the neural plasticity of the brain and what it means for consciousness.

Neural plasticity is a term that simply refers to the “…ability of the central nervous system (CNS) to adapt in response to changes in the environment or lesions.”[i]

Let’s start with babies. Why? Because babies are cute and Infant brains are amazing things! They are almost like soft, molding clay, in that they can be changed and shaped by so many of their first experiences – in ways that may seem surprising. Cats, for example, if kept in the dark during a critical period in their kittenhood, will never develop sight! This is just one example of how the neonatal mammal brain is malleable. Alva says that “in a very real sense the environment itself produces in us the conditions needed to experience that environment.”[ii]

But what is it about the makeup of our brain that enables us to have visual experiences as opposed to auditory or olfactory experiences? Be aware that this question is not just about vision, it is about consciousness itself. Remember the definition of consciousness – we think, we feel (i.e., we experience), the world shows up for us. What this question is about is determining the distinctive qualitative character of our “conscious episodes.” (Hmm. The older I get, the more episodic my memory gets, or at least it seems to.)

Scientists have been unable to answer this question. There is even a name for it – the “explanatory gap”, the difference between the neural states in our brain and the experience we are having. You may be looking at a red balloon, but if I peeked anywhere inside your head, I would never see what you are looking at, yet you are experiencing a red balloon.

Alva says that he is not at all surprised by the explanatory gap. He tells us that the reason we can’t explain the quality of this experience based entirely on brain events is that “there is nothing distinctively visual about the brain’s action.”[iii] Uh, say what?

He takes time to explain this for us, fortunately. In doing so, he recounts a very interesting experiment:

Ferret

A study was conducted at MIT by Mriganka Sur and colleagues involving newborn ferrets. In layman’s terms, what they did was to wire up the baby ferret’s eyes to the parts of the brain that are normally used for hearing. Technically speaking, what they did was to alter each ferret so that cells in the eye that would normally sprout connections into the visual areas of the brain (i.e., the visual thalamus, the visual cortex), would instead sprout connections into the areas of the brain normally used for hearing.

So what do you think happened? Did the ferrets suddenly start hearing with their eyes? This makes sense, right? The eye cells were connected to the auditory cortex, after all. But that’s not what happened. Instead what happened was that the rewiring enabled them to see with their auditory brains! Think about it. The part of the brain reserved (supposedly) for purely auditory activity suddenly grew the wiring necessary to support vision. That is so cool!

Alva calls this a “remarkable finding,” and I don’t think he’s wrong. It kind of blows my mind. It also goes to show just how malleable brains are. What Sur and his team did was to clearly demonstrate just how malleable the linkages are between the auditory and visual parts of our brain and they did this by completely undoing the normal way these brain parts are wired together.

You may not realize it, but this experiment with ferrets completely blew apart an assumption long-held by neuroscientists, namely that parts of our brain are preprogramed, designed and evolved from the get-go, if you will, to fulfill a particular purpose e.g., hearing, sight, smell, etc. And that is what makes this experiment kind of a big deal. This experiment is clear evidence that our neurons, the brain cells that comprise the area we know as the visual cortex, are really nothing special; at least, not in the sense that there is something that makes them specifically visual. Given the proper circumstances, the brain can suddenly say, “And now for something completely different!”[iv] So, if you are looking for evidence of a hard-wired connection between an experience you’re having and a group of specific brain cells, you will be disappointed. In the end, “The character of conscious experience can vary even though the neural activity underpinning it does not change.”[v] Thus, Alva tells us, it follows then, “…that what determines and controls the character of conscious experience is not the associated neural activity.”[vi]

[Reading about how plastic and malleable our brains really are reminded me that there was a cultural figure back in the 60’s and 70;s who was actively promoting and writing about how a specific drug could allow or enable you to rewire your own brain, an activity he highly recommended (no pun intended). I read his books and the theory then was (and still is) fascinating, at least to me. His name was Dr. Timothy Leary and the drug was LSD. I have actually experienced what I believe Leary was talking about, so this hit home. I should write about that sometime ?.]

Looking at experiments like the one done with the ferrets helps us “… get a handle on the relation between consciousness and the brain…”[vii] when analyzing situations where the normal correlation between neural activity and experience is altered.

Phantom Limb

Alva tells us of that we can use the fact of the brain’s plasticity to help us figure out why neural activity is “bound up with experience in the ways that it is.”[viii] So he wants us to look at another case where brain activity and our experience are a bit weird: the case of the phantom limb.[ix] We’ve all heard of this phenomenon, perhaps some of us have known someone with this condition. You lose a limb, but still feel like it’s attached. I mean you “really” feel it.

Sometimes people with phantom limb phenomena can be touched on the face and they then report that they feel the touch on their phantom limb. I had to think about this. So, what is happening here is that someone touches your face and you feel it in both the hand and the face, as if you had touched your own face. Strange, huh? Well, maybe, maybe not. It turns out that the area handling neural events involving our face (face cortex) is actually right next to the area in our brain handling our hands (hand cortex). It would seem then that losing a limb has somehow allowed these two brain areas to become entangled, allowing a touch to the face to appear as if it were a touch to a hand (now missing).

Alva explains that this entanglement between the face and hand cortices in our brain results in two “distinct effects.” First, the face cortex is activated in response to the touch on the face; and second, it produces an activation in the hand cortex corresponding to the feeling of being touched on the “now absent hand.” Alfa says this is similar to how a doorbell could turn on the lights if it had been wired to the light switch. Thus, “Touching the face simply brings about those neural effects that would have been brought about by the touching of the hand.”[x]

This then is a clear contrast with the ferret experiment. In the ferret experiment, the rewiring of the brain did not result in the ferrets being able to hear with their eyes, instead it allowed them to see with their auditory brains due to the auditory cortex changing its function (rewiring itself) for consciousness as a result of receiving stimulus from the eyes. In the phantom limb experiment, it’s the other way around. The phantom limb patient when touched on the face, feels it with his hand instead of feeling his face in his cortical hand area. Why? Because “the face is wired up to the hand area of the cortex.”[xi]

Alva tells us that we need to look “beyond the immediate neural activity” if we hope to understand why particular cells in certain areas of our brain behave in seeing and not in hearing, or vice versa. We won’t find it looking at just the brain cells. Activation of the hand cortex gives rise to the “…feeling of being touched on the hand even though the activation stems from touching the face, not the hand.”[xii]

So the question Alva asks now is: Why does changing the source of stimulation of a cortical area sometimes cause changes to the character of a resulting experience, like in the ferret example, and in other cases fail to do so, as in the phantom limb patient? He provides a detailed explanation at the end of his book, too detailed for me to describe here. But he also provides a short answer, one which he says he had provided us previously, namely: “What explains the consequences for consciousness of this sort of rewiring is not the intrinsic character of the neurophysiological changes themselves; it is, rather, the larger setting or context in which these neurophysiological changes occur.”[xiii]

Alva says the question that now must be posed is, “What is the relevant larger context in terms of which we can hope to understand the effects of neural rewiring on conscious experience? Put more simply, what are the contextual factors governing the character of experience and its relation to neural activity?”[xiv] He then promises to show us with the following chapters in his book, that the context “…must go beyond that of the brain itself to include the animal’s active relation to its surroundings.”[xv]

I’m going to hold him to it.

My next post on Alva’s philosophical concepts will get into the area of perception. Fun stuff!

[i] Wikipedia definition from US National Library of Medicine, National Institutes of Health.

[ii] Noe, Alva. Out of Our Heads: Why You Are Not Your Brain, and Other Lessons from the Biology of Consciousness (p. 50). Farrar, Straus and Giroux. Kindle Edition.

[iii] Noe, Alva. Out of Our Heads: Why You Are Not Your Brain, and Other Lessons from the Biology of Consciousness (p. 53). Farrar, Straus and Giroux. Kindle Edition.

[iv] Monty Python.

[v] Noe, Alva. Out of Our Heads: Why You Are Not Your Brain, and Other Lessons from the Biology of Consciousness (p. 54). Farrar, Straus and Giroux. Kindle Edition.

[vi] Ibid.

[vii] Ibid.

[viii] Ibid.

[ix] A phantom limb is the sensation that an amputated or missing limb is still attached. Approximately 60 to 80% of individuals with an amputation experience phantom sensations in their amputated limb, and the majority of the sensations are painful. (Wikipedia).

[x] Noe, Alva. Out of Our Heads: Why You Are Not Your Brain, and Other Lessons from the Biology of Consciousness (p. 55). Farrar, Straus and Giroux. Kindle Edition.

[xi] Ibid.

[xii] Ibid.

[xiii] Noe, Alva. Out of Our Heads: Why You Are Not Your Brain, and Other Lessons from the Biology of Consciousness (p. 56). Farrar, Straus and Giroux. Kindle Edition.

[xiv] Ibid.

[xv] Ibid.

Let us know what you think…

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Jeff Drake

Retired IT consultant, world-traveler, hobby photographer, and philosopher.