Comparing the brain areas supporting nondeclarative categorization and recognition memory.

Brain areas associated with both nondeclarative categorization and recognition memory were identified and contrasted using functional magnetic resonance imaging (fMRI) of healthy volunteers. Activity during dot-pattern categorization and recognition were compared with a control task (counting dots) in two separate groups of participants (n=5 each). The network of areas associated with nondeclarative categorization was found to include bilateral inferior prefrontal and parietal cortical areas that have been implicated in several other studies of categorization. During recognition, increased activity was found in posterior visual areas, the precuneus, posterior cingulate and right prefrontal cortex. Using the common control condition as a reference, recognition and categorization were contrasted and recognition was found to evoke more activity in posterior early visual cortex, the precuneus, right medial temporal lobe and right dorso-lateral prefrontal cortex. Previous research has implicated changes in visual representation in learning a category of dot-pattern by comparing activity evoked by categorical and non-categorical stimuli. The current findings support those results and additionally identify brain areas active during categorization that are involved in expressing this category knowledge.