Influence of premorbid personality and location of lesion on emotional expression.

Both premorbid personality characteristics and location of brain lesion have been proposed to account for emotional changes after cerebral damage. To explore the relative merits of each hypothesis, we compared the MMPI profiles of 30 epileptic patients, who showed either a euphoric or depressive reaction after injection of amobarbital into the right or left hemisphere, with the MMPI profiles of 30 matched controls. There were no significant T-score differences between euphoric, depressed, or control patients on any of the MMPI scales. However, more patients with euphoric (42%) than depressed (0%) reactions had hypomania (scale 9) scores greater than 70 T. With regard to location of lesion, there was a statistically significant association between emotional reaction and side of amobarbital brain inactivation. Euphoria was more frequent following right, and depression was more common after left, hemisphere inactivation. Although support was found for both premorbid personality and lesion location in the genesis of emotional reactions after brain damage, results were more robust for location of lesion.