Philosophical Foundations of Neuroscience. P. M. S. Hacker
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showing on the left the underside of a normal human brain and on the right of a brain from a person suffering from congenital mental weakness. Reproduced with the permission of the library of St John’s College, Oxford
Clinico-pathological correlations in the nineteenth century
The nineteenth century saw a flowering of the clinico-pathological correlation of cortical areas with psychological powers, such as vision and speech. It might seem straightforward to identify abnormal behaviour(s) uniquely due to the loss of a psychological power, but this is not necessarily so, as behaviour exhibits such a variety of different forms.1 Furthermore, identifying at an autopsy the unique site of a lesion or degeneration is difficult at any time, let alone with no more than the tools available in the nineteenth century. Even when considering a comparatively straightforward power in this regard, such as vision, it took fifty years before the primary visual cortex was agreed upon as located in the occipital lobe.2 Nevertheless, significant progress was made by Broca, as well as Fritsch, Hitzig and others, together with Sherrington’ s researches on primates.
Single neuron investigations and fMRI in the twentieth century:primacy of behaviour
In the twentieth century the correlations revealed following careful application of the clinico-pathological technique were followed by neuroscientific investigations into the neural mechanisms operating within the identified cortical areas. The introduction of new techniques by Adrian and Eccles in the first half of the twentieth century allowed for a new level of spatial resolution relating psychological powers and cortical function, namely that of a neuron within the already identified cortical area, such as those of Blakemore in the visual occipital cortex. However, these new technologies and those introduced later in the century, such as functional magnetic resonance imaging (fMRI), did not change the basic logic that in order to understand the function of the cortex, whether at the level of anatomical parts or that of single neurons, correlations must be made with that of the experiencing, behaving animal or human that is under study. Of course, study of cellular mechanisms, such as excitatory synaptic transmission, can be understood at the mechanistic level without reference to behaviour, but to understand their relevance within a particular cortical region requires reference through correlations with the behaviour and experiences of the animal.
Misascription of psychological attributes to parts of the cortex andto neurons
The twentieth century saw the growth of the misascription of psychological powers to parts of the cortex and to neurons rather than to the experiencing, behaving human possessing the cortex with its neurons. The experimental attempt over the past two thousand years to understand the functions of the brain have matured along the only path that is logically possible, namely: seeking correlations of the kind described above. However, the realization of this has been increasingly lost over the history of neuroscience to the present day. This is manifest in researchers asserting that the particular cortical area or neuron under study is the experiencing agent, forgetting that it is the correlations of that area/neuron with human experience and behaviour that identified the region under consideration in the first place. It might be argued that Blakemore, Zeki, Damasio, Tononi and many others are simply ascribing psychological predicates to different cortical areas and their neurons as a convenient shorthand, but an appraisal of their work shows that not to be the case. Clearly this is untenable.
2 Philosophical Problems in Neuroscience: Their Conceptual Roots
The history of neuroscience shows that our understanding of cortical function is founded of necessity on correlations with human behaviour and experience. We now consider a different approach, based on logico-grammatical grounds, to the question of whether psychological attributes (seeing, thinking, remembering, etc.) can be attributed to a part of the cortex, either an anatomical part or a group of neurons.
Psychological attributes are attributes of the sentient creature as a whole
This approach was initiated by Aristotle in the fourth century bc. Aristotle states in his De Anima that ‘To say that the psuche¯ is angry is as if one were to say that the psuche¯ weaves or builds. For it is surely better not to say that the psuche¯ pities, learns, or thinks, but that the man does these things with his psuche¯.’ Here Aristotle is emphasizing that pitying, learning and thinking can be sensibly attributed only to human beings, not to some principle of life that informs their body, namely the psuche¯ (sometimes incorrectly translated as ‘soul’). In the nineteenth century Lewes restated Aristotle’ s conception in its modern form. In his The Physical Basis of Mind (1891) he states that ‘It is the man and not the brain, that thinks; it is the organism as a whole and not one organ that feels and acts.’ In the twentieth century Wittgenstein offers the same thought in his Philosophical Investigations (1953), ‘Only of a living human being and what resembles (behaves like) a living human being can one say: it has sensations, it sees; is blind; hears; is deaf; is conscious or unconscious.’
Aristotle, Lewes and Wittgenstein are pointing out that there are no logico-linguistic grounds for attributing psychological predicates to the brain, parts of the brain, or indeed any other parts of the body, rather than to behaving human beings. The logic of part/whole relations is known as mereology. The misattribution of psychological predicates by many neuroscientists we call the mereological fallacy in neuroscience. The conceptual confusions arising from this fallacy, together with the fact that the history of cognitive neuroscience is a search for correlations with behaviour, makes clear that it is humans that experience, not their brains or parts of their brains.
Notes
1 1 M. R. Bennett, S. Hatton, D. F. Hermens and J. Lagopoulos, ‘Behavior, neuropsychology and f MRI’, Progress in Neurobiology, 145–146 ( 2016), pp. 3–6.
2 2 Ibid., p. 17.
1 The Growth of Neuroscientific Knowledge: The Integrative Action of the Nervous System
The conceptual framework for early investigations into the biological basis for human sensory, volitional and intellectual capacities was set by Aristotle’ s philosophical writings on the psuchē and pneuma. The early growth of neuroscientific knowledge was dominated by the question of how the contraction of muscles involved in voluntary movements of limbs is effected. However, Aristotle’ s own rudimentary investigations, which led him to believe that the blood vessels initiate muscle contraction, were a false start. It was, above all, Galen’ s much later discoveries of the nerve supply to muscles from the spinal cord that made it clear that it is the nerves that carry out this function. Galen’ s work initiated 2,000 years of enquiry into how the spinal cord and brain are involved in voluntary movement and into the reflex origins of some movements. The identification of motor and sensory spinal nerves, the role of the spinal cord in reflex movements, and the relationship between the action of the brain and the spinal cord in voluntary and reflex movement were all resolved by experiments. These involved observations on muscles and limbs following lesions to different parts of the nervous system. In this way a conception evolved of how the functions of the brain, spinal cord and nerves are integrated to give the final motor output.
The conceptual framework within which neuroscientific knowledge grew originated in Aristotelian thought, but it was subsequently transformed by the Cartesian revolution in the seventeenth century. In this chapter we shall adumbrate the development of ideas concerning the neural basis of animate functions, concentrating increasingly upon what Sherrington, among the greatest of neuroscientists, called ‘the integrative action of the nervous system’, as it applies to movement. This sketch of the history of the slow growth of knowledge about the nervous system and its operations will display some of the conceptual difficulties encountered by natural philosophers