Paticia S. Churchland, "Tuching A Nerve" 에서 (2)

 

철학자 Daniel Dennett 의 From Bacteria to Bach and Back:

The Evolution of Minds (2017) 와 Consciousness Explained

(1991) 를 '읽어볼 만한' 부분만 읽고 나니 전에 읽은, 역시 철학자인,

Patricia Churchland 의 Touching a Nerve (2013) 가 생각났다.

도서관에서 또 빌려서, 읽다 보니 재미에, 반쯤을 다시 읽었다.

Touching a Nerve 가 잘 쓴, 권하고 싶은 책이다. (상식 수준의

논리를 대단한 듯 '철학'이라고 부르기 좋아하는 그런 철학자의 장황한

글은 참고 읽기 힘들다.)

 

Touching a Nerve 에 대해서는 지난 2015년 1월에도 올렸었다

(Churchland, "Touching a Nerve" 에서 (1)).

 

 

 

 

 

 

      

 

 

Patricia S. Churchland, Touching a Nerve: The Self As Brain (2013)

[오른쪽 사진: 주문해서 산, 부제가 Our Brains, Ourselves 로 바뀐, paperback (2014)]

 

 

The soul was supposed to be indivisible, not divisible like a walnut. But there they were, the split-brain results, available for all to see: if the brain's hemispheres are disconnected, mental states are disconnected. Those results were a powerful support for the hypothesis that mental states are in fact states of the physical brain itself, not states of a nonphysical soul. (p 50)

 

The explanation of how procaine blocks the transmission of pain signals is satisfying because it provides details of mechanism, it can easily be tested, and the details fit with what else we know experimentally about pain and neurons. Such "fitting with the rest of the body of knowledge" is called consilience: the greater the consilience, the greater the coherence and integration of phenomena and facts. Note, however, that consilience is not a guarantee that the explanation is right... (p 51)

 

If free will is illusory means that there is no difference between a brain with self-control and one lacking self-control or one with diminished self-control, that claim is flatly at odds with the facts.... [T]hose differences are entirely real and quite a lot is known about the neurobiology of those differences.... I am bound to say that I suspect that the claim that free will is an illusion is often made in haste, in ignorance. (p 184)

 

Normal speech is under the guidance of nonconscious mechanisms. You become conscious of precisely what you unconsciously intended to say only when you said it. (p 198)

 

Yes, language is important to human cognition, but some philosophers, such as Dan Dennett, have given it what, from the perspective of the brain, is an exaggerated importance.... Dennett, for example, has long argued that only those with language are actually conscious. (p 203)

 

The first point for self versus nonself is that solving the "what is moving' problem is very, very basic in the evolution of animal nervous system. ... The platform for the solution to the problem is this: movement-planning signals in one part of the brain are looped back to the sensory and more central regions of the brain, telling them, in effect, "I am moving this-a-way." ... [T]he movement-planning signal that gets looped back is usually called an efference copy -- copy of a my-movement signal... [A]ll this separating of the source of movement is handled without conscious intervention. You just know. (p 209)

 

Reports of patients with bilateral insula damage but preserved self-awareness suggest that self-awareness is multidimensional, implicating an interconnected set of regions, probably including, as Antonio Damasio has long argued, the brainstem. (p 218)

 

Aristotle understood, as did many later philosophers, including certainly David Hume and Adam smith, that emotions play an important role in wise decision making. (p 222)

 

Aristotle made the point that developing good habits as early as possible is a sound if not infallible guide to living well. ... And often those habits provide the unconscious compass concerning what is relevant and what is not. (p 223)

 

The more I learned about nonconscious processes in the brain and how they seamlessly interweave with the conscious processes, the more I began to realize that to understand consciousness, we need to understand more about those nonconscious processes. (p 224)

 

According to [Nicholas] Schiff's hypothesis [in 2008], to be conscious of anything requires activity from a ribbon of neutrons in the middle of the thalamus, whose activity is itself regulated by neurons in the brainstem, an evolutionarily very old structure. Called the central thalamus (also called the intralaminarnuclei of the thalamus), its neurons have pathways, though sparse, to the top layer of every part of cortex. That organization is unique and suggests that consciousness involves the upregulation of the entire cortex, whereas the reverse, loss of consciousness is related to downregulation. In both cases, the changes are dependent on the activity of neurons in the central thalamus. (p 234)

 

Here is another striking fact about neurons in the central thalamus. There are looping neurons from these upper layers of cortex projecting right back to the ribbon in the central thalamus. The looping back allows for maintaining an especially potent but transient connection for a chunk of time, as, for example, while paying attention to a particular sensory event or feeling. (p235)

 

[T]he ribbon of neurons that is the central thalamus is controlled by activity in the brainstem and in turn regulates the cortical neurons to ready themselves for concsious business. (p 236)

 

Wisely, Baars avoided trying to identify the essence of consciousness, realizing that essences are an old-fashioned way of thinking about phenomena that impede making actual progress. This contrasts with the approach favored by some philosophers.... Baars called his framework the gloval workspace theory .... Workspace draws on the idea that consciousness is a consumer of products of lower-level processing, that other functions such as decision making and planning can access what is in consciousness. Hence the workspace is global. (p 241)

 

When the visual signal dog is masked (not consciously perceived), only early visual areas (in the back of the brain) show activation. By contrast, when the visual signal is consciously seen, the posterior activity spread to more frontal regions, including parietal, temporal, and prefrontal areas. [Stanislas] Dehaene  and Changeux refer to this as global ignition. This pattern of posterior to frontal spreading of activity seems to uphold Baar's hunch that conscious perception involves global connectivity in the brain, whereas unconscious perception is restricted to a smaller region. (p 243)

 

A robust signature of conscious perception -- a waveform in the scalp recordings - occurs about 300 milliseconds after the stimulus is presented.... This result suggests that the back-to-front global ignition required to yield awareness of a sensory stimulus takes about 300 milliseconds. (p 245)

 

You do not want to be so skeptical that you learn little and fail to take advantage of scientific progress. You do not want to be so smug that you think you have nothing to learn from science.... [Y]ou do not want to selectively believe the results you happen to favor. Cherry picking, as such selectivity is called, is a recipe for self-deception. (p 261)

 

Science is an extension of common sense. It is common sense gone systematic. Einstein put it well: one thing I have learned in a long life: that all our science, measured against reality, is primitive and childlike -- and yet it is the most precious thing we have." Slamming that comment as scientism would be nothing short of silly. (p 264)