Three proposed experiments are directed at a better understanding of the role of prefrontal cortex in categorization under different strategies, with a focus on four cognitive processes: response inhibition, maintenance of stimulus features in working memory, manipulation of information in working memory, and directed search of long term memory. Although prefrontal cortex has traditionally been associated with rule induction and shifting from one rule to another, our initial event-related potential (ERP) study comparing multidimensional rule use, unidimensional rule use, and a multidimensional similarity strategy for categorizing novel visual stimuli showed similar large late prefrontal potentials for subjects using both of the multidimensional strategies as compared to the unidimensional rule. Proposed Exp. 2 examines the impact of maintaining multiple stimulus attributes in working memory (WM) on this late prefrontal activity, by manipulating the number of stimulus dimensions relevant to a specified categorization rule. The impact of rule dimensionality (hypothesized to influence the maintenance component of WM) is contrasted to a manipulation of rule complexity (conjunctive versus exclusive-OR), hypothesized to tax a theoretically separate aspect of working memory - the manipulation of information. Proposed Exp. 3 examines the interaction between WM and long-term memory representations of stimulus attributes relevant to category assignment, by comparing categorization judgments based solely on the contents of WM versus those that require retrieval of information from long term memory. Finally, Exp. 1 pursues a finding of the preliminary study that was unique to multidimensional rule use: an early prefrontal potential that was larger for stimuli close to the boundary between two categories as compared to stimuli far from the category boundaries, and thus more typical of their categories. We hypothesize that this frontal N2 component reflects inhibition of responses based on preliminary perceptual analyses when information consistent with an alternative, incompatible response is detected. Exp. 1 tests the hypothesis that one role of prefrontal cortex in categorization is to inhibit responses based on fast perceptual processes in order to allow slower analyses to run to completion when a rule-based judgment should be based on the slower analyses. The experimental design thus contrasts stimuli that are globally similar to the prototype (and individual exemplars) of one category although belonging to a different category according to the rule to stimuli for which global similarity and the rule both suggest the same response.
| Folstein, Jonathan R; van Petten, Cyma (2011) After the P3: late executive processes in stimulus categorization. Psychophysiology 48:825-41 |
| Folstein, Jonathan R; Van Petten, Cyma; Rose, Scott A (2008) Novelty and conflict in the categorization of complex stimuli. Psychophysiology 45:467-79 |
| Folstein, Jonathan R; Van Petten, Cyma (2008) Influence of cognitive control and mismatch on the N2 component of the ERP: a review. Psychophysiology 45:152-70 |
