within the modules and between the modules. A key component of the hypothesis is that the unity of conscious experience is provided by the self-conscious mind and not by the neuronal machinery of the liaison areas of the cerebral cortex. Hitherto it has been impossible to develop any neurophysiological theory that explains how a diversity of brain events comes to be synthesized so that there is a unified conscious experience … My general hypothesis regards the neuronal machinery as a multiplex of radiating and receiving structures ( modules). The experienced unity comes, not from a neurophysiological synthesis, but from the proposed integrating character of the self-conscious mind. I conjecture that in the first place the raison d’être of the self-conscious mind is to give this unity of the self in all its conscious experiences and actions.(HM 227f.)
How does the mind engage in this activity of synthesis (or ‘binding’)? Eccles suggested that the mind
plays through the whole liaison brain in a selective and unifying manner. The analogy is provided by a searchlight. Perhaps a better analogy would be some multiple scanning and probing device that reads out from and selects from the immense and diverse patterns of activity in the cerebral cortex and integrates these selected components, so organizing them into the unity of conscious experience … Thus I conjecture that the self-conscious mind is scanning the modular activities in the liaison areas of the cerebral cortex … From moment to moment it is selecting modules according to its interests, the phenomena of attention, and is itself integrating from all this diversity to give the unified conscious experience.(HM 229)
Four flaws in Eccles’s conception
The metaphors are striking, and have echoes in current neuroscientific theory.20 Nevertheless, Sperry’s discoveries have none of the dramatic implications that Eccles imputed to them. There are four flaws in Eccles’s conception to which we wish to draw attention.
(1) The phenomena resultant upon hemispherectomy were misdescribed
First, the phenomena were misdescribed. It is not just the neural activities of the right hemisphere that are unknown to the subject – all the activities of the brain are unknown to subjects, who do not, after all, perceive their own brains (and, even if they could, do not have electron microscopes for eyes). It is true that the right hemisphere cannot ‘express itself in language’, any more than the right leg – because there is no such thing as a part of a human being expressing itself in language (see §§3.1–3.4). So the left hemisphere cannot ‘express itself in language’ either. The right hemisphere is not able ‘to disclose any experience of consciousness’ that we can recognize, because there is no such thing as a subordinate part of a human being being conscious. As will be argued in detail in chapter 3, it is only human beings (and other animals) who are conscious (or unconscious), and conscious of (or not conscious of) various things – not their subordinate parts. The left hemisphere is equally lacking in ‘any experience of consciousness’. Finally, the left hemisphere has no ‘verbal and ideational abilities’, although the verbal and ideational abilities of normal human beings are causally dependent upon the normal functioning of the left hemisphere.21
(2) The ‘self-conscious mind’ is not an entity of any kind
Second, the so-called self-conscious mind is not an entity of any kind, but a capacity of human beings who have mastered a reflexive language. They can therefore ascribe experiences to themselves and reflect on the experiences thus ascribed (see §14.6). But the ‘self-conscious mind’ is not the sort of thing that can intelligibly be said to be ‘in contact with’ the brain ( let alone with something denominated ‘the liaison brain’).
(3) Incoherence in Eccles’s hypothesis
Third, Eccles’s main hypothesis is unintelligible. If the self-conscious mind were, per impossibile, ‘actively engaged in reading out’ from areas in the dominant hemisphere and ‘selecting from these modules according to attention’, then the self-conscious mind would have to perceive or be aware of the neural modules in question (otherwise how could it ‘read them out’?), and know which ones to select for its purpose (otherwise the wrong ones might constantly be selected). Or, to put matters more lucidly, for any of this story to make sense, human beings would have to be aware of the neural structures and operations in question, and, from moment to moment, decide which ones directly to activate, and, of course, have the capacity to do so. But we possess no such knowledge and no such capacity.
(4) The very notion of the self-conscious mind presupposes the unity of experience
Finally, it is confused to suppose that the raison d’être of the ‘self-conscious mind’ is to engender the unity of the self and, as our contemporaries would put it, ‘solve the binding problem’. For any talk of a person or of a human being as having a mind already presupposes the unity of experience and cannot be invoked to explain it.
Eccles’s errors cannot be rectified by substituting the brain for his conception of the ‘self-conscious mind’
Eccles’s dualism was misconceived. Contemporary neuroscientists are eager to dissociate themselves from his doctrines and to dismiss his ideas as silly. This is misguided. Eccles had the courage to face difficult problems and to pursue his ideas about them to their logical conclusions. That his ideas are wrong is true, and much can be learned from the errors in question. It is, however, a sad mark of how little many neuroscientists have learned from Eccles’s struggles that they apparently believe that the problems that Eccles’s interactionist dualism was designed to answer can be solved by substituting the brain for Eccles’s ‘self-conscious mind’. Problems regarding how the mind can bring about movements of the muscles and limbs by acts of will are not solved by supposing, as Libet does (see §9.2), that it is the brain that decides what muscles and limbs to move. Although it is misguided to suppose that the mind is in liaison with the left hemisphere, it is no less misconceived to suppose, as do Sperry, Gazzaniga and Crick (see §17.3), that the hemispheres of the brain know things, have beliefs, think and guess, hear and see. For these are functions of human beings and other animals, not of brains or half-brains (which enable human beings to exercise those functions). And, as we have noted, although it is confused to suppose that the mind scans the brain, it is equally confused to suppose that the brain must scan itself in order to generate awareness or self-consciousness – as if it lay in the nature of self-consciousness that it necessarily involves a self-scanning process, if not of the mind, then of the brain. In short, the lessons that can be learned from Eccles’s failure have largely yet to be learned. We shall endeavour to show this in some detail in later chapters.
2.4 Wilder Penfield and the ‘Highest Brain Mechanism’
Penfield’s training
Wilder Penfield (1891–1976) was born in Spokane, Washington. After graduating from Princeton in 1913, he won a Rhodes Scholarship to Oxford and entered the School of Physiology there to begin his medical studies under the inspiring influence of Sherrington. He followed Sherrington’s interest in histology and, in particular, in neurocytology. After obtaining his BA in physiology at Oxford, he went to the Johns Hopkins Medical School, where he finished his medical degree in 1918. His first research concerned changes in the Golgi apparatus of neurons after axonal section. In 1924 he began to study the healing processes of surgical wounds in the brain. On Sherrington’s advice, he spent some time in Madrid working with Pio del Rio-Hortega, learning to use the histological methods of his brilliant teacher Ramón y Cajal. To this end, surgical specimens of brain scars were collected from patients who had been operated on for post-traumatic epilepsy.
Penfield’s achievement
Penfield
