The organization of thinking: What functional brain imaging reveals about the neuroarchitecture of complex cognition

Abstract

The relationship of the mind to the brain has established itself at the forefront of scientific interest in large part because of the rapid development of functional magnetic resonance imaging (fMRI). Exciting new findings have often been expressed in the form of compelling images that indicate that brain areas become activated in various tasks or fail to activate in various special populations. These brain images appear to tell a simple and straightforward story. The invited inference is that a one-to-one mapping exists between the activation of brain areas and the execution of certain psychological processes, such as the process of perceiving a face. At first glance, this story imposes some order on the results; some consistencies emerge across brain imaging studies, and some imaging results seem to be related to studies of brain lesions in neuropsychological patients. But the consistencies are limited in scope, and the mapping between the infinity of possible tasks and the finite-indeed, rather small-number of activating brain areas identified by neuroimaging techniques is greatly underdetermined, if not logically troubling. We propose that the idea of a one-to-one mapping of cortical activation to high-level cognitive processes that is suggested by the brain activation images is incorrect-a gross oversimplification of a more complex (and more interesting) many-to-many mapping, governed by more subtle organizational principles. In brief, we argue that thinking is a network phenomenon and suggest the beginnings of a theory of the organization of cortical networks.This article explores how the various cortical areas that subserve cognition might function in conjunction with each other. The main objectives are to specify the operating principles that govern the complex, dynamic, and adaptive relationships among brain areas and to relate brain function to cognitive function. It is not our goal here to specify the cognitive specializations of each brain area, although to describe how areas work together, we necessarily have to hypothesize the cognitive endowments of some brain areas. We believe there is value in developing a theory of how various brain areas collaborate in order to realize cognitive information processing, despite the remaining uncertainty about the functional specializations of the individual areas.As functional imaging provides progressively finer detail about brain activation, computational modeling provides a theory-building workspace in which the new pieces of information can be put together and their cofunctioning can be examined. In this workspace, the component mechanisms can be specified in detail and their ability to account for the observed phenomena can be tested, as a few initial attempts have shown (Arbib, Billard, Iacoboni, & Oztop, 2000; Fincham, Carter, van Veen, Stenger, & Anderson, 2002;Horwitz & Tagamets, 1999;Just, Carpenter, & Varma, 1999). One of the goals of this study is to instantiate the operating principles in a cognitive neuroarchitecture, 4CAPS, that has been develop...

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