Vol. 7, No. 2, 2001 Page 1 
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Vol. 7, No. 2, 2001 Page 1 |
A new Finnish study suggests that altered development of the hippocampus, a horseshoe-shaped region in the temporal lobes of the brain, plays a role in psychopathic behavior.
Mikko Laakso et al. measured the hippocampal volumes of 18 antisocial alcoholic offenders, using magnetic resonance imaging (MRI). The researchers report that higher scores on tests of psychopathic behavior correlated strongly with smaller volume of the posterior half of the hippocampus.
A previous study by the same researchers found that in nonviolent, late-onset alcoholics, hippocampal volume is reduced and declines with age-an indication of acquired damage. In contrast, the hippocampal volumes of the sociopathic alcoholic subjects, while also reduced, actually increased with age. This suggests "profound biological differences" between the two types of alcoholics, Laakso et al. say, "and raises the possibility that the observed effects within the [psychopathic] category are due to other factors than the cumulative acquired effects related to alcohol abuse, such as primary personality psychopathology."
The hippocampus is involved in memory, learning, and emotional regulation. Studies of rodents suggest that lesions of the dorsal hippocampus lead to impaired fear conditioning, and Laakso et al. say their data are consistent with the theory that "one of the central features in the birth of psychopathy is a deficit in acquisition of conditioned fear."
The researchers say more study is needed to determine whether their findings are relevant to non- alcoholic and/or non-violent psychopaths. However, they note, violence and substance abuse are nearly universal among antisocial individuals.
Laakso and colleagues conclude, "[W]hile it is clear that psychopathic and violent behavioral traits are not exclusively based on the integrity of the hippocampus, the results of this study may provide a significant step in the quest toward isolating the very neural circuits that... predispose one to psychopathic behavioral traits."
"Psychopathy and the posterior hippocampus," M. P. Laakso, O. Vaurio, E. Koivisto, L. Savolainen, M. Eronen, H. J. Aronen, P. Hakola, E. Repo, H. Soininen, and J. Tiihonen, Behavioural Brain Research, Vol. 118, No. 2, January 29, 2001, pp. 187-193; and, "A volumetric MRI study of the hippocampus in type 1 and 2 alcoholism," M. P. Laakso, O. Vaurio, L. Savolainen, E. Repo, H. Soininen, H. J. Aronen, and J. Tiihonen, Behavioural Brain Research, Vol. 109, 2000, pp. 177-186. Address: M. P. Laakso, Department of Neurology, Building 5, Kuopio University Hospital, P.O. Box 1777, 70211, Kuopio, Finland, mikko.laakso@uku.fi.