The brainstem auditory evoked potential asymmetry is replicable and reliable.

Lateralization of neural function is generally thought to occur only at the level of the cerebral cortex and perhaps the thalamus. Levine and McGaffigan [EEG Clin. Neurophysiol. 55, 532-537, 1983] challenged this view by identifying a neural asymmetry at the level of the brainstem. They analyzed brainstem auditory evoked potentials (BAEPs) and found that peak III(+) amplitude (baseline-to-peak) was significantly larger in response to right than to left ear stimulation. The current paper demonstrates that this BAEP asymmetry is (a) reliable within and between subjects, (b) present for 33/sec and 10/sec click rates, and (c) more reliable when amplitude is measured peak-to-peak. This brainstem asymmetry may reflect the general tendency of humans to orient rightward and/or may be a precursor of higher level asymmetries.