Abstract
One of the most important requirements for making accurate decisions is setting an appropriate decision criterion. To study behavioral and neural correlates of the decision criterion, we have trained subjects to categorize a set of stimuli that can vary continuously along one dimension (length of lines or speed of moving dots). At the beginning of each trial, a cue instructed the subjects on how to set their decision criterion for categorizing the stimuli as “short/long” or “slow/fast”. Depending on the cue, the subjects were required to bias their decisions toward “short/slow” or toward “long/fast”. Behavioral analyses indicate that this task minimizes the effects of previous trials and stimulus specific biases, and allows us to dissociate neural activity related to categorization vs. response selection. Subjects performed the task during event-related fMRI to determine which areas correlate with different decision variables. There were two versions of the task: one in which the criterion was cued explicitly and one in which it was cued implicitly. In addition, a match/non-match task was used to control for activation associated with stimulus specific working memory. We identified neural networks involved in specifying the criterion, categorizing the stimulus, and selecting the response.