Abstract
The aim of this study is to examine the effects of unilateral cerebral lesions on MLRs.
Five patients had either temporal lobe or/and subcortical lesions resulting from cerebrovascular accidents. All patients were normal in pure tone audiometry and in ABR. All patients had ear extinctions which were ascertained by dichotic listening test.
Neuro-electrical activity was recorded at 3 scalp locations in the coronal plane. Electrodes were sited Cz, C6 (halfway between T4 and C4), C5 (halfway between T3 and C3). MLRs were elicited by 90 dBpeSPL clicks at a rate of 2/sec with earphones. During testing, the patients were awake and resting comfortably on the bed. Evoked responses were measured from average of 700 responses with a duration of 200 ms.
According to the MLR records, Pa was largest on the intact hemisphere and was absent on the lesioned side.
These results support the hypothesis that Pa is bilaterally generated by two vertically oriented dipole sources located about the temporal lobes.
