The prefrontal cortex has long been suspected to play an important role in cognitive control, in the ability to orchestrate thought and action in accordance with internal goals. Its neural basis, however, has remained a mystery. Here, we propose that cognitive control stems from the active maintenance of patterns of activity in the prefrontal cortex that represent goals and the means to achieve them. They provide bias signals to other brain structures whose net effect is to guide the flow of (...) activity along neural pathways that establish the proper mappings between inputs, internal states, and outputs needed to perform a given task. We review neurophysiological, neurobiological, neuroimaging, and computational studies that support this theory and discuss its implications as well as further issues to be addressed. (shrink)

The scientific, ethical, and policy issues raised by research involving the engraftment of human neural stem cells into the brains of nonhuman primates are explored by an interdisciplinary working group in this Policy Forum. The authors consider the possibility that this research might alter the cognitive capacities of recipient great apes and monkeys, with potential significance for their moral status.

This chapter presents some rather different ideas about the organization of the prefrontal cortex. Rather than fixed functional specialization, it emphasizes adaptability of neural coding to fit a behavioral context. In particular, it presents both neuroimaging and single-unit electrophysiological evidence to suggest that, in selected regions of the prefrontal cortex, neurons adapt their properties to code just that information of relevance to current behavior. This adaptation is a major contributor to the achievement of cognitive focus and control. Although this adaptive (...) coding model recognizes important regional specializations within the prefrontal cortex, it suggests a perspective on these that is rather different from that presumed in the traditional divide-and-conquer approach. (shrink)