The Brain's Representational Power by Cyriel M.A. Pennartz

Author:Cyriel M.A. Pennartz
Language: eng
Format: epub
Publisher: MIT Press
Published: 2016-11-13T00:00:00+00:00

8

Requirements for Conscious Representations

In the act of diving into shallow water a young soldier experienced a sudden pain in the neck and at once lost the power of his limbs. He was pulled out of the water by his comrades and soon regained some power in the left upper and lower limbs. […] On the left side of the body profound sensory changes of an unusual character were found on the trunk and lower limb […]. The patient replied to all forms of stimuli, but the sensations evoked by the different forms of stimulation were all described as similar. Tactile, pressure, thermal and pain stimuli were not recognized as such, but were described as “queer” or “funny,” “like electricity” or as “making him laugh.”

—R. M. Stewart (1925)

8.1 Integration

Up to this point, we have particularly highlighted what the problems are when trying to build conscious representations using neurons. It is much less clear how to solve these problems, at least conceptually. Phenomenal consciousness remains the ultimate enigma in mind–brain science as it has been in the past, and no ready-made solutions can be jotted down. What we can do is first begin to outline the requirements that a brain system needs to fulfill to generate a conscious representation (this chapter), and then get a handle on the neural mechanisms realizing these requirements (in chapter 9).

Most likely, the brain remains conscious when “stripped” from its capacities for emotion, episodic memory, and motor functions. What would be the bare-bones necessities for a “minimal” brain system sustaining conscious sensations? Classic neural network models are insufficient to provide such a basis, among other reasons because they fail to explain why it is that we experience some sensory inputs as visual and others as olfactory. A related problem entails that neural-network-like structures abound elsewhere in nature, even in inorganic form, and this problem of panpsychism resurfaces when we consider accounts based on information theory. If we probe the demands that a conscious system actually poses and try to translate these demands into plausible neural mechanisms, will we then still face the same panpsychic trap, or will we arrive at a brain system sufficiently specific to be distinct from inanimate systems?

Viewing the problem of consciousness from a bottom-up anatomical and physiological perspective, we saw that an appropriate brain infrastructure is not enough to sustain consciousness. Thalamocortical and associated systems not only should be wired up correctly but also should assume an appropriate physiological state to do the job. Job fitness is all too easily lost when we fall into the oblivion of deep sleep or inhale an anesthetic gas. In the case of anesthesia, local cortical processing retains an uncanny similarity to conscious states. So why is it then—in the face of such local processing capacities—that the entire system fails to meet the requirements for conscious processing?

Let us first go back to the rock-bottom biological function of consciousness. Organisms roaming about in an environment full of threats and opportunities for survival and reproduction face the representational problem of needing rapid updates about the world around them and about their own states (see chapter 6).

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