Dichotic-listening measures of brain laterality in mania.

Dichotic syllable and complex tone tests were used to compare performance asymmetries in manic patients (n = 35) with normal controls (n = 26) and to determine whether there were changes in laterality with remission of the manic state. Relationships of performance asymmetries to treatment outcome and symptom features were also examined. Compared with normal controls, manic patients showed overall poorer accuracy, particularly for complex tones presented to the left ear, and they failed to show the normal left-ear (right-hemisphere) advantage for complex tones. Abnormal laterality for complex tones was present in patients who later responded to treatment but not in nonresponders. In the euthymic state, patients showed improved left-ear accuracy for complex tones and more normal perceptual asymmetry. These findings suggest that mania is associated with a decrement in right-hemisphere processing of complex tonal information.