Functional specificity in the human brain: A window into the functional architecture of the mind

June 22, 2010
Nancy Kanwisher

Understanding the nature of the human mind is arguably the greatest intellectual quest of all time. It is also one of the most challenging, requiring the combined insights not only of psychologists, computer scientists, and neuroscientists but of thinkers in nearly every intellectual pursuit, from biology and mathematics to art and anthropology. Here, I discuss one currently fruitful component of this grand enterprise: the effort to infer the architecture of the human mind from the functional organization of the human brain.
The idea that the human mind/brain is made up of highly specialized components began with the Viennese physician Franz Joseph Gall  (1758–1828). Gall proposed that the brain is the seat of the mind, that the mind is composed of distinct mental faculties, and that each mental faculty resides in a specific brain organ. A heated debate on localization of function in the brain raged over the next century, with many of the  major figures in the history of neuroscience weighing in (Broca, Brodmann, and Ferrier in favor, and Flourens, Golgi, and Lashley opposed). By the early 20th century, a consensus emerged that at least basic sensory and motor functions reside in specialized brain regions.
The debate did not end there, however. Today, a century later, two questions are still fiercely contested. First, how functionally specialized are regions of the brain? The concept of functional specialization is not all or none but a matter of degree; a cortical region might be only slightly more engaged in one mental function than another, or it might be exclusively engaged in a single mental function. Many neuroscientists today challenge the strong (exclusive) version of functional specialization. As one visual neuroscientist put it, “each extrastriate visual area, rather than performing a unique, one-function analysis, is engaged, as are most neurons in the visual system, in many different tasks”.
The second ongoing controversy concerns the question of whether only basic sensory and motor functions are carried out in functionally specialized regions, or whether the same might be true even for higher-level cognitive functions. Although one might think that Broca settled this matter with his demonstration that the left frontal lobe is specialized for aspects of language, the current status of this debate is far from clear. Indeed, a recent authoritative review of the brain-imaging literature on language concludes that “areas of the brain that have been associated with language processing appear to be recruited across other cognitive domains”. The case of language is not unique. Indeed, a backlash against strong functional specialization seems to be in vogue. A recent neuroimaging textbook argues that “unlike the phrenologists, who believed that very complex traits were associated with discrete brain regions, modern researchers recognize that … a single brain region may participate in more than one function”.
(www.pnas.org. Adaptado.)

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