Topographical Analysis of Adolescent Affective Disorders

Abstract

This study evaluated the EEG spectral content and the components of the cognitive ERPs evoked by a visual sustained-selective attention task from adolescents diagnosed as having an affective disorder and those who did not (nonreferred controls, CON) to determine if there were different electrophysiological profiles associated with major subtypes of affective disorders; i.e., Dysthymic Disorder (DysD) and Cyclothymic Disorder (CycD). Distinctive ERP and EEG profiles were found to be associated with the DysD and CycD groups. While both groups of depressives presented diminished P3b amplitudes, the DysD group showed a relatively greater suppression over the right temporal regions, whereas the CycD group exhibited relatively greater suppression over the left temporal region. In addition, there were differences with respect to the earlier components associated with information processing. For instance, the PI was found deficient in the DysD group as compared to the other groups, whereas the N2 component was deficient in the CycD group as compared to the CON and DysD groups. In contrast to these amplitude differences, no significant latency differences were seen with respect to any component elicited by this paradigm. With respect to the EEG spectra, the CON group showed greater relative power in the Beta range than either the CycD or the DysD group, with the depressives featuring more midline frontal Theta activity. Characteristically, both depressant groups showed a greater anterior distribution of Alpha activity. In addition, the foci of the various spectral bands for the DysD subjects were shifted away from the right hemisphere as was the case for the P3b. Overall, the profiles suggested that those who fit the diagnostic classification of DysD have deficit function in right post-Rolandic zones, along with anomalous frontal function. It was also suggested that there may be a core disturbance of physiological arousal in unipolar depression. The CycD subjects, on the other hand, featured no hemispheric bias with respect to the P3b components or spectral foci, but did show similar features of being cortically “hypoaroused,” so that actively depressed adolescent CycD subjects did share certain physiological features with unipolar subjects.

Key Words:

• Major Depression
• Bipolar Disorder
• Topographical mapping