Neuropsychological processing associated with recovery from depression after stereotactic subcaudate tractotomy

Objective: The authors compared patients who underwent stereotactic subcaudate tractotomy for depression, who were still depressed or recovered from depression, to identify therapeutic mechanisms. Method: Ten depressed and eight recovered psychosurgery patients, along with nine never-depressed subjects and nine who had recovered from depression with medication, completed the Iowa Gambling Task, a measure of decision making in the face of feedback. Psychosurgery patients also completed general neuropsychological testing. Results: Recovered psychosurgery patients exhibited insensitivity to negative feedback on the Iowa Gambling Task compared to the other three groups. This difference between the groups remained when general neuropsychological performance was covaried out. Conclusions: These findings suggest acquired relative insensitivity to negative information as a specific mechanism mediating the antidepressant effect of stereotactic subcaudate tractotomy. Such insensitivity is not secondary to deficits in general neuropsychological functioning and is not a function of recovery from depression per se.