Distinct behavioral effects of prefrontal and parietal cortex inactivations on an accumulation of evidence task in the rat

Jeffrey C. Erlich, Bingni W. Brunton, Chunyu A. Duan, Timothy D. Hanks and Carlos D. Brody, eLife 2015;4:e05457

Jeff Erlich

Gradual accumulation of evidence for decision-making (which we also study in Brunton et al. 2013 and Hanks*, Kopec*, et al. 2015) is thought to be a core process for many different types of decisions. Numerous brain regions have been shown to have neural correlates of it. But which brain regions are necessary for it? Local inactivations are the only way to address that question and have been surprisingly little-used.

Here, in rats performing an auditory evidence accumulation task, we inactivated the frontal orienting fields (FOF) and posterior parietal cortex (PPC), two rat cortical regions that have neural correlates of accumulating evidence and that have been proposed as central to decision-making. We used a detailed model of the decision process to analyze the effect of inactivations. Inactivation of the FOF induced substantial performance impairments that were quantitatively best described as an impairment in the output pathway of an evidence accumulator with a long integration time constant (>240 ms). In contrast, we found a minimal role for PPC in decisions guided by accumulating auditory evidence, even while finding a strong role for PPC in internally-guided decisions.

First-author Jeff Erlich is now faculty at NYU-Shanghai.