Tuesday, June 26, 2007

The Four Ages of Functional Neuroimaging: Part 1

In the increasingly interdisciplinary world of the science of human behavior, a certain conversation can be heard again and again in the gathering places where the practitioners of neuroscience and cognitive psychology are occasionally found together. The neuroscientist, having patiently listened to a psychologist present his latest theoretical model – resplendent with the boxes and arrows constituting the “mental modules” of some particular piece of the cognitive system – shakes his head, wondering aloud what possible relevance these chalkboard chimera might have to someone who studies the live matter of the brain. The cognitive psychologist of a certain stripe takes a similar view of the neuroscientists’ efforts, which he or she maintains sheds very little light on the functional properties of the mind. Both camps argue for epistemological supremacy: cognitive psychology for the ghost in the machine, and neuroscience for the machine in the ghost. Standing somewhere in the middle, amid the crosstalk, straining to be heard above the din of argument, stands the cognitive neuroscientist, unsure of which camp he is addressing (or belongs to), but nevertheless confident that he holds the key, the answer to the debate. “We must study both”, he asserts. “We must study the ghost in the machine and machine in the ghost!”

Unfortunately, the cognitive neuroscientist is not unlike the spurned and neglected offspring of two parents that despise each other and consider their child a wastrel and, ultimately, a mistake. Indeed, it is only after the cognitive neuroscientist succeeds in gaining the attention of his audience (in this hypothetical gathering) that psychology and neuroscience turn towards their wayward child and nod their heads and point their fingers in disdainful unison. If there is one thing they can agree on, it is that cognitive neuroscience and its favored technological toy -- functional magnetic resonance imaging (fMRI) -- has nothing to offer them. By the same token, functional neuroimaging and cognitive neuroscience, generally, taking the remarkable success of the movement as a self-evident mark of its scientific worth and validity, has never made a particularly sustained or rigorous effort to make the case for why functional neuroimaging matters to neuroscience and cognitive psychology.

In the last year, however, this has begun to change. Advocates of functional neuroimaging in a number of review papers have laid out a formal case for the legitimacy and relevance of the field. Most of the recent discussion, particularly articles by Henson (2005), Poldrack (2006) and De Zubicaray (2006) has been aimed at cognitive psychology, and has argued for both the relevance and theoretical benefits that functional neuroimaging can bring to the field of cognitive psychology. In a recent issue of the journal Cortex, however, Coltheart (2006) and Page (2006) forcefully argued the position that, essentially, functional neuroimaging has so far contributed nothing to cognitive psychology. A number of examples suggesting how neuroimaging had indeed informed cognitive psychology were then proffered in response, but Coltheart remained unconvinced. It is the purpose of the present article, not to rehash the debate or contribute a technical innovation with regard to the inference in functional neuroimaging, but rather to provide a slightly different perspective on the debate, and to show that, perhaps, this recent flare up arises out of a basic disagreement (or confusion) over what such terms as ”mind”, “mental”, “cognitive process”, and “cognitive theory” really mean.

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