The normal scalp topography of the middle latency auditory evoked potential Pa component following monaural click stimulation.

The scalp topography of the middle latency auditory evoked potential (MLAEP) Pa component following left and right ear click stimulation was investigated in 15 normal hearing and neurologically intact right-handed subjects. An unbiased reference was employed. The Pa component showed a broad voltage field that was recorded maximally at the Cz and Fz leads regardless of which ear was stimulated. A broad negative voltage field that occurred coincident in time with the Pa component was recorded posterior to the T3, P3, Pz, P4 and T4 electrode leads. This negative voltage field peaked in amplitude at the T5, O1, Oz, O2, and T6 electrode leads. An unexpected finding was that the peak latency of the Pa component occurred significantly earlier following stimulation of the right ear.