during cortical stimulation of the brain during operations). So, when the mind needs to retrieve a memory, in a flash it opens the files of remembrance in the brain through the highest brain mechanism (MM 49).
Penfield’s interpretation of phenomena consequent on electrode cortical stimulation
Reflection on some of the phenomena consequent on cortical stimulation during operations led Penfield to similar conclusions. So, for example, a patient, whose ‘speech cortex’ was interfered with by an electrode, exhibited exasperation when he could not identify a picture of a butterfly. On withdrawal of the electrode, he said, ‘“Now I can talk. Butterfly. I couldn’t get the word “Butterfly”, so I tried to get the word “moth”!’ It is interesting to see how Penfield construed and explained this temporary impairment of the patient’s normal identificatory powers.
It is clear that while the speech mechanism was temporarily blocked he could perceive the meaning of the picture of a butterfly. He made a conscious effort to ‘get’ the corresponding word. Then, not understanding why he could not do so, he turned back for a second time to the interpretative mechanism … and found a second concept that he considered the closest thing to a butterfly.24 He must then have presented that to the speech mechanism, only to draw another blank.(MM 52)
According to Penfield, concepts are stored away in the mind’s concept mechanism in the brain, from which the mind selects the concept it requires. That concept is then presented in the stream of consciousness, and if the mind approves of the selection, the highest brain mechanism flashes this non-verbal concept to the speech mechanism, which, when functioning normally, will present to the mind the word that is appropriate for the concept (MM 53).
Penfield was equally impressed by the fact that when neural stimulation to the brain caused a hand movement, the patient invariably responded, ‘I didn’t do that. You did.’ And equally, when cortical stimulation caused vocalization, the patient said, ‘I didn’t make that noise. You pulled it out of me.’ It was striking that no form of electrical stimulation to the cortex could induce a patient to believe or to decide (MM 77). It is not surprising that Penfield drew the conclusion that belief and volition are functions of the mind.
The mind and its interaction with the brain via ‘the highest brain mechanism’
A man’s mind, Penfield concluded, is the person (MM 61). It is the mind that is aware of what is going on, that reasons and decides, and understands (MM 75f.). The person walks about the world, depending always upon his ‘private computer’ (i.e. his brain), which he programs continuously (MM 61). The highest brain mechanism is the meeting place of mind and brain, the psychophysical frontier (MM 53). The mind, in making decisions, causes the highest brain mechanism to send neuronal messages to other mechanisms in the brain, and data stored in the brain are admitted to consciousness. How is interaction effected? Here Penfield speculated that there must be a second form of energy (other than the electrical energy that is used by the highest brain function to innervate the nervous system) which is available to the mind. This, he conjectured, must be made available to the mind in its waking hours by the highest brain mechanism.
The mind vanishes when the highest brain mechanism ceases to function due to injury or due to epileptic interference or anaesthetic drug. More than that, the mind vanishes during deep sleep.
What happens when the mind vanishes? There are two obvious answers to that question; they arise from Sherrington’s two alternatives – whether man’s being is to be explained on the basis of one or two elements. (MM 81)
Penfield thought it preposterous to suppose that the mind is merely a function of the brain, and so ceases to exist when it ‘vanishes’ in sleep or epileptic automatism and is re-created afresh each time the highest brain mechanism functions normally. Rather, he concluded, the mind is ‘a basic element’, and has a ‘continuing existence’. ‘One must assume’, he wrote, ‘that although the mind is silent, when it no longer has its special connection to the brain, it exists in the silent intervals and takes over control when the highest brain mechanism goes into action’ (MM 81). So, the highest brain mechanism switches off the power that energizes the mind whenever one goes to sleep, and switches it on again when one awakens.
Is the explanation improbable?, Penfield queried.
It is not so improbable, to my mind, as is the alternative expectation [explanation] – that the highest brain mechanism should itself understand, and reason, and direct voluntary action, and decide where attention should be turned and what the computer must learn and record, and reveal on demand. (MM 82)
Penfield’s neo-Cartesianism
Penfield’s neo-Cartesianism is no advance over that of Sherrington and Eccles. But if we are to learn anything from his errors, we must not simply dismiss them as misguided and move on to other matters. That will merely ensure that we learn nothing from his endeavours. We must ask what went wrong, what drove one of the greatest neurosurgeons and neurologists of all times to embrace such a misconceived view of the mind and brain?
Shared presuppositions
(1) The Cartesian conception of the mind
It should be noted that there are at least two fundamental presuppositions that Penfield shared with Sherrington and Eccles. The first was a Cartesian conception of the mind. Like Descartes, Penfield conceived of the mind as an independent substance (or, as he puts it, ‘a fundamental element’ that has ‘continuing existence’). Like Descartes, he identified the person, the ‘I’, or the ‘self’ with the mind, rather than with the living human being. Like Descartes, he took the mind to be the bearer of psychological attributes,25 and consequently conceived of human beings as subjects of psychological predicates only derivatively. And, like Descartes, he took the mind to be a causal agent that can bring about changes in the body by its actions.
(2) The assumption that the question of whether brain mechanisms can account for the mind is an empirical one
The second presupposition is that the question which so deeply disturbed him – namely, whether brain mechanisms account for the mind, whether the mind can be explained by reference to what is known about the brain – is an empirical question. Like Sherrington, Penfield conceived of the matter as a choice between two different empirical hypotheses. Either we can explain everything the mind does – for example, thinks and believes, reasons and concludes, has wants, forms intentions and purposes, and decides to act – by reference to neural states and events, or we must conceive of the mind as an independent substance in immediate causal interaction with the brain, and hence with the body. The choice between these two hypotheses is to be determined by the evidence that supports them severally and by their relative explanatory powers.
Criticisms of Penfield’s presuppositions:
(1) Misconceptions about the nature of the mind
Both presuppositions are misconceived. The mind, as we have already intimated, is not a substance of any kind. Talk of the mind is merely the form in which we represent to ourselves human powers and their exercise and talk about human powers and their exercise. We say of a creature (primarily of a human being) that it has a mind if it has a certain range of active and passive powers of intellect and will – in particular, conceptual powers of a language-user that make self-awareness and self-reflection possible. The idioms that involve the noun ‘mind’ have as their focal points thought, memory and will. And they are all readily paraphrasable into psychological expressions in which the word does not occur (we shall discuss this matter in some detail in §4.8).
A
