Electroencephalographic and reaction time asymmetries to musical chord stimuli

EEG was recorded over left and right hemispheres at temporal leads (T3, T4) referred to the vertex (Cz) in 16 right-handed male subjects. Musical chords were presented randomly in monaural sequence, during a task which required a selective motor response to stimuli presented to one ear. The integrated amplitude of the 8-13 Hz alpha rhythm was measured when subjects listened passively. Under all conditions, a lower mean alpha amplitude was recorded over the right hemisphere than the left, regardless of which ear was stimulated. Alpha suppression over the right temporal area was accentuated when the performance task directed attention to the stimulus. Reaction time to left ear stimulation was shorter than that for the right ear. With monaural stimulus presentation behavioral asymmetry, and various EEG asymmetries can be observed. There is hemispheric asymmetry associated with attention to task relevant stimuli indicated by reduction in the alpha rhythm over the right temporal area and asymmetry in reaction time with greater efficiency of the left ear to muscial chords.