Prefrontal cortex regulates inhibition and excitation in distributed neural networks

Prefrontal cortex provides both inhibitory and excitatory input to distribu ted neural circuits required to support performance in diverse tasks. Neuro logical patients with prefrontal damage are impaired in their ability to in hibit task-irrelevant information during behavioral tasks requiring perform ance over a delay. The observed enhancements of primary auditory and somato sensory cortical responses to task-irrelevant distracters suggest that pref rontal damage disrupts inhibitory modulation of inputs to primary sensory c ortex, perhaps through abnormalities in a prefrontal-thalamic sensory gatin g system. Failure to suppress irrelevant sensory information results in inc reased neural noise, contributing to the deficits in decision making routin ely observed in these patients. In addition to a critical role in inhibitor y control of sensory flow to primary cortical regions, and tertiary prefron tal cortex also exerts excitatory input to activity in multiple sub-regions of secondary association cortex. Unilateral prefrontal damage results in m ulti-modal decreases in neural activity in posterior association cortex in the hemisphere ipsilateral to damage. This excitatory modulation is necessa ry to sustain neural activity during working memory. Thus, prefrontal corte x is able to sculpt behavior through parallel inhibitory and excitatory reg ulation of neural activity in distributed neural networks. (C) 1999 Elsevie r Science B.V. All rights reserved. PsycINFO classifications: 2346; 2520; 2 530; 2540; 3213; 3297.