primate brain that Sherrington had carried out, and which have been described above. In 1928 he went to Breslau to work with Otfrid Foerster, to learn his method of gentle electrical stimulation of the cortex of epileptic patients while they were under local anaesthesia during the excision of epileptogenic scar tissue. During these procedures he learned the method of operating under local anaesthesia, using electrical stimulation to identify the sensory and motor cortex to guide the surgical excision. This technique was to be used to singular effect by Penfield in Montreal, where, in 1934, he established the famous Montreal Neurological Institute at McGill University, which was devoted to the study and surgical treatment of focal epilepsy. Such stimulation made it possible to locate exactly the position of the sensorimotor cortex and of the cortex subserving speech, so that these vital areas could be spared during the surgical excision. In some instances the stimulation might activate the more excitable epileptogenic cortex and reproduce a portion of the patient’s habitual seizure pattern. This enabled the surgeon to identify the site of the physiologically deranged epileptic focus. Penfield’s mastery of these procedures was subsequently summarized in a series of monographs on brain surgery for epilepsy.
Penfield noted in 1938 that stimulation of certain parts of the temporal cortex in patients occasionally excited the vivid recall of previous experiences. It became evident that almost half of the patients afflicted with epilepsy had seizures that could be shown to originate in one or other of the temporal lobes. This work on temporal lobe epilepsy led to very important observations regarding the hippocampus and memory function, as well as the localization of the cortex subserving the latter. By 1951 Penfield, together with Milner, had shown that removal of one hippocampus on the medial aspect of the temporal lobe resulted in severe memory disorder in patients who were later found to have damage to the hippocampus on the opposite side. Thus the bilateral loss of function of the hippocampus led to the complete inability of these patients to remember any post-operative occurrence. This memory loss was not accompanied by any loss of intelligence or attentive capacity. Penfield’s analyses of the electrical stimulation of the cortex of 1,132 conscious patients undergoing brain surgery greatly extended our knowledge of functional localization, especially with regard to memory and to that most human of capacities, speech.
Penfield’s methodological commitment
Already in his student days, Penfield had had a ‘sense of wonder and a profound curiosity about the mind’. When he turned from the study of the animal to the human brain, his ‘planned objective’, he later wrote, was ‘to come to understand the mechanisms of the human brain and to discover whether, and perhaps how, these mechanisms account for what the mind does’.22 Studying under Sherrington, he came to ‘the realization that the brain was an undiscovered country in which the mystery of the mind of man might someday be explained’. He was, of course, fully aware of Sherrington’s views on the relation of mind and brain. In the final paragraph of the foreword to his great book The Integrative Action of the Nervous System (1906), Sherrington had remarked, ‘That our being should consist of two fundamental elements offers, I suppose, no greater inherent improbability than that it should rest on one only.’ Penfield, however, took the view that the neuroscientist should endeavour to explain the behaviour of animals, including humans, on the basis of neuronal mechanisms alone. Only if that failed, he thought, should one have recourse to alternative forms of explanation. And throughout his career as a neurosurgeon, he retained this methodological commitment.
Penfield on the mind
Towards the end of a long life dedicated to neurosurgery and neurology, Penfield published a small volume entitled The Mystery of the Mind. This was, he wrote, ‘the final report of my experience’ – an overview of what he had achieved in respect of his youthful objective. ‘The nature of the mind’, he averred, ‘presents the fundamental problem, perhaps the most difficult and most important of all problems’ (MM 85). What he wished at last to do, he wrote in the preface, was to ‘consider the evidence as it stands, and ask the question Do brain mechanisms account for the mind? Can the mind be explained by what is now known about the brain?’ (MM, xiii). Referring explicitly to the above-quoted remark of Sherrington’s, Penfield judged that ‘the time has come to look at his two hypotheses, his two “improbabilities”. Either brain action explains the mind, or we must deal with two elements’ (MM 4). Despite his methodological commitment, Penfield found himself driven towards a Cartesian view not unlike that of his great teacher. ‘For my own part’, he wrote,
after years of striving to explain the mind on the basis of brain-action alone, I have come to the conclusion that it is simpler (and far easier to be logical) if one adopts the hypothesis that our being does consist of two fundamental elements … Because it seems to me certain that it will always be quite impossible to explain the mind on the basis of neuronal action within the brain, and because it seems to me that the mind develops and matures independently throughout an individual’s life as though it were a continuing element, and because a computer (which the brain is) must be programmed and operated by an agency capable of independent understanding, I am forced to choose the proposition that our being is to be explained on the basis of two fundamental elements. This, to my mind, offers the greatest likelihood of leading us to the final understanding toward which so many stalwart scientists strive. (MM 80)
What led him to this conclusion? Two features in particular had impressed Penfield. First, given his specialization in epilepsy cases, he was, unsurprisingly, impressed by the phenomena of epileptic automatism. Second, he was powerfully struck by the responses elicited from patients in reaction to electrode stimulation during surgery.
Penfield’s interpretation of epileptic automatism
A patient, suffering an epileptic seizure that has induced automatism, will often continue to execute whatever more or less stereotypical tasks he was engaged in. He will, however, be in a fugue condition – that is, after recovery he will remember nothing of what he has done during the seizure. Penfield interpreted automatism as showing that the epileptic seizure disconnected the mind from what, following Hughlings Jackson,23 he called ‘the brain’s highest mechanism’ (a precursor of Eccles’s ‘liaison brain’). He took it that the brain, during the period of automatism, is controlling the behaviour of a ‘human automaton’ in accordance with antecedent ‘programming’ by the mind. Just as the programming of a computer comes ‘from without’, so too the programming of the brain, which is, Penfield claimed, a biological computer, is effected by the mind via the brain’s highest mechanism. Purpose comes to it from outside its own mechanisms. Short-term programming obviously serves a useful purpose, making possible automatic continuation of routine tasks, and this is visibly and strikingly manifest during periods of such epileptic seizures.
That this highest mechanism, most closely related to the mind, is a truly functional unit is proven by the fact that epileptic discharge in gray matter that forms a part of its circuits, interferes with its action selectively. During epileptic interference with the function of this gray matter … consciousness vanishes, and with it goes the direction and planning of behaviour. That is to say, the mind goes out of action and comes into action with the normal functioning of this mechanism.
The human automaton, which replaces man when the highest brain-mechanism is inactivated, is a thing without the capacity to make completely new decisions. It is a thing without the capacity to form new memory records and a thing without that indefinable attribute, a sense of humour. The automaton is incapable of thrilling to the beauty of a sunset or of experiencing contentment, happiness, love, compassion. These, like all awarenesses, are functions of the mind. The automaton is a thing that makes use of reflexes and skills, inborn and acquired, that are housed in the computer. (MM 47)
Though Penfield ventured no testable hypotheses about how this interaction occurs, he claimed that the highest brain mechanism is, as it were, the mind’s executive. It accepts directions from the mind, and passes them on to the various mechanisms of the brain (MM 84). The mind directs the brain in action. It has no memory of its own. But the contents of
