Ventral and Dorsal Prefrontal Activity as a Function of Target Probability

Abstract:
Activation of the prefrontal cortex was examined as a function of target probability during a Go-NoGo task using functional magnetic resonance imaging (fMRI). Ten right-handed adults were scanned. It was hypothesized that increasing the number of nontargets relative to targets would increase interference among stimuli and result in increased dorsal prefrontal activity. Likewise, we hypothesized that increasing the number of responses relative to nonresponses would increase interference among responses and result in increased ventral prefrontal activity. Data were pooled across subjects and analyzed as a 10 (subjects) X 3 (target probabilities of high, mid, and low) ANOVA with contiguity threshold of 3 pixels and p < .001. As predicted, dorsal prefrontal activity significantly increased when the probability of targets was low (.23%)and ventral prefrontal activity increased when the probability of targets was high (.95%). In addition, dorsal prefrontal activity decreased (.21%) during high target probabilities and ventral prefrontal activity decreased (.94%) during low target probabilities. (Supported by NIMH K01 award - 1K01MH01297)