Neuroanatomical bases of electrodermal hypo-responding: a cluster analytic study

Schizophrenics and other psychiatric patients have been found to have a high incidence of electrodermal hypo-responding. Different neural mechanisms may underlie hypo-responding in these groups. The present study utilized cluster analysis of magnetic resonance imaging (MRI) and electrodermal orienting data to examine the neuroanatomical correlates of electrodermal hypo-responding in 15 schizophrenics, 15 psychiatric controls (predominately affective disorders), and 15 normal controls. The number of electrodermal responses was recorded during a standard orienting paradigm. MRI scans were obtained, yielding area measures for the pre-frontal cortex and lateral ventricle-brain ratios (VBRs). The number of electrodermal orienting responses and the MRI measures were transformed into zeta-scores and entered into an agglomerative hierarchical cluster analysis, which yielded three clusters. A 3 x 3 Chi-square analysis revealed that the three clusters significantly differed according to diagnostic group. Analyses of variance (ANOVAs) revealed that the first two clusters had significantly fewer electrodermal orienting responses than the third cluster (predominately normals). Further, the first cluster (predominately schizophrenics) had significantly smaller frontal lobes than the other two clusters. Additionally, the three normals in the first cluster had relatively high levels of schizotypy. The second cluster (predominately affective disorders) had significantly larger VBRs than the other two clusters. Schizophrenics in the three clusters differed with respect to gender composition and positive symptoms. Thus, diminished pre-frontal area may underlie electrodermal hypo-responding in a subgroup of schizophrenics and schizotypals, while enlarged ventricles may underlie the same phenomenon in the affective disorders and another subgroup of schizophrenics.