BRAIN ERPS OF DEPRESSED-PATIENTS TO COMPLEX TONES IN AN ODDBALL TASK - RELATION OF REDUCED P3 ASYMMETRY TO PHYSICAL ANHEDONIA

Event-related potentials to binaural complex tones were recorded from 40 depressed outpatients and 22 normal control participants at 30 elec trode sites. Patients did not differ from control participants in N1 o r P3 amplitude but showed greater N2. N2 was greater over right than o ver the left hemisphere at lateral sites in patients and control parti cipants. A P3 asymmetry was found for control participants and patient s with low scores on a physical anhedonia scale, but not for patients with high anhedonia scores. Topographic (local Laplacian) maps corresp onding to P3 showed greater radial current flow over right than over l eft central regions in control participants. Patients with high anhedo nia did not show this asymmetry, whereas patients with low anhedonia s howed an intermediate asymmetry. These findings support the hypothesis that anhedonic depression is associated with dysfunction of right hem isphere mechanisms mediating the processing of complex pitch informati on.