Vol. 7, No. 2, 2001 Page 6&7 
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Vol. 7, No. 2, 2001 Page 6&7 |
German researchers re-port that functional magnetic resonance imaging (fMRI) reveals unusual patterns in antisocial individuals participating in an "emotional learning" task.
Frank Schneider et al. studied 12 adult males with antisocial personality disorder, and 12 control subjects. All subjects were exposed to pictures of faces with neutral expressions, which were then paired with either a neutral stimulus (room air) or an aversive stimulus (the smell of rotten yeast). Both groups of subjects developed a negative response to the neutral face that was paired with the rotten smell, indicating that both displayed behavioral conditioning.
However, Schneider et al. say, "Although patients with antisocial personality disorder showed no general impairment in behavioral conditioning, they demonstrated divergent neuronal network activity related to normal subjects" in brain areas shown by previous research to function abnormally in psychopaths.
In particular, they note, fMRI showed greater brain activity in the amygdala and dorsolateral prefrontal cortex of psychopaths during the part of the task in which the neutral faces were paired with either aversive or neutral stimuli. This increased activity, they say, "may be a result of the additional effort put in by this group to perform our aversive conditioning task since the process that was involved may have demanded more resources from primarily emotionally deficient individuals."
In addition, antisocial subjects responded differently during the initial habituation phase, in which all stimuli were presented in random order. While normal subjects exhibited a pattern of amygdala activation in response to the unpleasant odor, antisocial subjects exhibited a pattern of deactivation. Schneider et al. say this is consistent with other studies showing that antisocial individuals show reduced responses to aversive and intense stimuli, "which may explain their lack of response towards punishment."
"Functional imaging of conditioned aversive emotional responses in antisocial personality disorder," Frank Schneider, Ute Habel, Christoph Kessler, Stefan Posse, Wolfgang Grodd, and Hans-Wilhelm Muller-G„rtner, Neuropsychobiology, Vol. 42, 2000, pp. 192-201. Address: Frank Schneider, Department of Psychiatry, University of Dusseldorf, Bergische Landstrasse 2, D-40629, Dsseldorf, Germany.