Separating sustained from transient aspects of cognitive control during thought suppression.

Cognitive theories of how people regulate their thoughts have suggested the involvement of two control processes that occur over different time courses. These cognitive accounts parallel recent neural models of executive control, which suggest that the prefrontal cortex (PFC) mediates sustained changes in the allocation of control processes, whereas the anterior cingulate cortex (ACC) relays a transient need for additional control. Combining these cognitive and neural models of control, we used recently developed analysis techniques to distinguish transient from sustained changes in brain activation while subjects attempted to suppress an unwanted thought. Results were consistent with both models: Dorsolateral PFC demonstrated sustained increases in activation during attempts at thought suppression, whereas bilateral ACC demonstrated transient increases associated with occurrences of unwanted thoughts. These data support proposals regarding the different contributions made by the PFC and ACC to executive control and provide initial neuroimaging support for dual-process models of how individuals regulate their thoughts.

Medial prefrontal activity differentiates self from close others.

A key question in psychology and neuroscience is the extent to which the neural representation of others is incorporated with, or is distinct from, our concept of self. Recent neuroimaging research has emphasized the importance of a region in the medial prefrontal cortex [MPFC; Brodmann's area (BA) 10] when performing self-referent tasks. Specifically, previous studies have reported selective MPFC recruitment when making judgments about the self relative to a familiar but personally unknown other. The present event-related functional magnetic resonance imaging study extends these findings to judgments about personally known others. Subjects were imaged while making trait adjective judgments in one of the three conditions: (i) whether the adjective described the self; (ii) whether the adjective described an intimate other (i.e., a best friend); or (iii) whether the adjective was presented in uppercase letters. Making judgments about the self relative to an intimate other selectively activated the MPFC region previously implicated in the self-processing literature. These results suggest that while we may incorporate intimate others into our self-concept, the neural correlates of the self remain distinct from intimate and non-intimate others.

An fMRI investigation of the impact of interracial contact on executive function.

We investigated whether individual differences in racial bias among white participants predict the recruitment, and potential depletion, of executive attentional resources during contact with black individuals. White individuals completed an unobtrusive measure of racial bias, then interacted with a black individual, and finally completed an ostensibly unrelated Stroop color-naming test. In a separate functional magnetic resonance imaging (fMRI) session, subjects were presented with unfamiliar black male faces, and the activity of brain regions thought to be critical to executive control was assessed. We found that racial bias predicted activity in right dorsolateral prefrontal cortex (DLPFC) in response to black faces. Furthermore, activity in this region predicted Stroop interference after an actual interracial interaction, and it statistically mediated the relation between racial bias and Stroop interference. These results are consistent with a resource depletion account of the temporary executive dysfunction seen in racially biased individuals after interracial contact.

Neural correlates of thought suppression.

The present report used functional magnetic resonance imaging (fMRI) to examine the neural correlates of thought suppression. Subjects were imaged while alternately (i) attempting to suppress a particular thought, (ii) attempting to suppress all thoughts, or (iii) thinking freely about any thought. Suppression of a particular thought, when compared to the free-thought control condition, revealed greater activation in the anterior cingulate. When the task of suppressing all conscious thoughts was compared to free-thought, a more distributed network of brain regions, including the anterior cingulate and the insula, was activated. These findings are consistent with previous research on cognitive control and may provide potential insights into psychological disorders involving recurring, intrusive thoughts.