Brainstem auditory evoked potentials recorded around the human upper brainstem area.

The intracranial spatiotemporal distributions of brainstem auditory evoked potentials were analyzed in two patients with epilepsy to study the dipole directions of waves III and V, previously found to have a horizontal and a vertical dipole, respectively. Depth electrodes were implanted bilaterally into the frontal and temporal lobes of these patients, the targets including the amygdala and hippocampus which are close to the upper pons and midbrain. Recordings around the upper pons and from the subcortical area downwards along the dorsal aspect of the upper pons indicated that waves III and V are constructed of mixed dipoles, wave III also having a vertical dipole segment and wave V also a horizontal one. These results suggest that several neural activities from the upper pons to midbrain contribute to the generation of waves III and V.