Event-related potentials to binaural complex tones
were recorded from 40 depressed outpatients and 22 normal
control participants at 30 electrode sites. Patients did
not differ from control participants in N1 or P3 amplitude
but showed greater N2. N2 was greater over right than over
the left hemisphere at lateral sites in patients and control
participants. A P3 asymmetry was found for control participants
and patients with low scores on a physical anhedonia scale,
but not for patients with high anhedonia scores. Topographic
(local Laplacian) maps corresponding to P3 showed greater
radial current flow over right than over left central regions
in control participants. Patients with high anhedonia did
not show this asymmetry, whereas patients with low anhedonia
showed an intermediate asymmetry. These findings support
the hypothesis that anhedonic depression is associated
with dysfunction of right hemisphere mechanisms mediating
the processing of complex pitch information.