Review of brain functioning in depression for semantic processing and verbal fluency

Abstract

Neurobiological models of depression point to brain regions that are proposed to be involved with both emotion regulation and language processing. This qualitative review focused on neurophysiological evidence for semantic processing and verbal fluency deficits associated with left frontal lobe and dorsolateral prefrontal cortex functioning in depression, respectively. Findings suggest that there are no behavioral or neurophysiological evidence of performance differences between depressed and healthy individuals for semantic processing of neutral information, arguing against generalized left frontal lobe deficits. However, the preponderance of evidence points to enhanced processing of negative information in both left and right frontal lobes and behavior. Studies of verbal fluency were limited to non-emotional information. The majority of studies evaluated phonemic verbal fluency in depression (e.g., producing words that begin with a particular letter) and results generally showed bilateral hypoactivation of the frontal lobe with no concomitant deficits in behavioral performance. Overall, semantic processing and verbal fluency studies did not provide substantive evidence of specific left frontal lobe deficits. Evidence that emotional information may differentially impact brain functioning relative to neutral information in depression suggests that examination of verbal fluency for emotional information may contribute to the elucidation of executive functioning processes associated with the dorsolateral prefrontal cortex in depression.