Psychopathy and the posterior hippocampus.

Neurobiology of psychopathy is of interest, not only because neural underpinnings of psychopathy remain obscure, but also because psychopaths may provide a model to study violent behavior, neurology of morals and impaired decision-making. Medial temporal lobe pathology has been suggested to be a part of the neural systems dysfunction which manifests as violent and psychopathic behavior. Yet, so far no sound evidence of neuroanatomical correlates for psychopathic behavior has been found. In this study regional hippocampal volumes were measured using magnetic resonance imaging in 18 habitually violent offenders with antisocial personality disorder and type 2 alcoholism (derived from forensic psychiatric evaluation). The regional volumes along the anteroposterior axis of the hippocampus were correlated with the subjects' degree of psychopathy as evaluated by the Psychopathy Checklist-Revised. Strong negative correlations, up to -0.79, were observed, among the study subjects, between the psychopathy scores and the posterior half of the hippocampi bilaterally. These data are in accordance with experimental studies proposing that lesions of the dorsal hippocampus impair acquisition of conditioned fear, and with theories on psychopathology according to which one of the central features in the birth of psychopathy is a deficit in acquisition of conditioned fear.