Context: Despite the repeated findings of impaired fear conditioning and affective recognition in psychopathic individuals, there has been a paucity of brain imaging research on the amygdala and no evidence suggesting which regions within the amygdala may be structurally compromised in individuals with psychopathy.
Objective: To detect global and regional anatomical abnormalities in the amygdala in individuals with psychopathy.
Design: Cross-sectional design using structural magnetic resonance imaging.
Setting: Participants were recruited from high-risk communities (temporary employment agencies) in the Los Angeles, California, area and underwent imaging at a hospital research facility at the University of Southern California.
Participants: Twenty-seven psychopathic individuals as defined by the Hare Psychopathy Checklist-Revised and 32 normal controls matched on age, sex, and ethnicity.
Main outcome measures: Amygdala volumes were examined using traditional volumetric analyses and surface-based mesh modeling methods were used to localize regional surface deformations.
Results: Individuals with psychopathy showed significant bilateral volume reductions in the amygdala compared with controls (left, 17.1%; right, 18.9%). Surface deformations were localized in regions in the approximate vicinity of the basolateral, lateral, cortical, and central nuclei of the amygdala. Significant correlations were found between reduced amygdala volumes and increased total and facet psychopathy scores, with correlations strongest for the affective and interpersonal facets of psychopathy.
Conclusions: Results provide the first evidence, to our knowledge, of focal amygdala abnormalities in psychopathic individuals and corroborate findings from previous lesion studies. Findings support prior hypotheses of amygdala deficits in individuals with psychopathy and indicate that amygdala abnormalities contribute to emotional and behavioral symptoms of psychopathy.