Simultaneous and time-staggered dichotic speech perception after total hemispherectomy: evidence of release from competition.

In normals, time-staggering a pair of dichotically presented CVs leads to a 'lag effect.' After anterior temporal lobectomy, the lag effect disappears, but the lesion-ipsilateral ear still shows the effects of some residual competition by virtue of its continuing to perform at less than 100% intelligibility. By contrast, after total hemispherectomy, the lesion ipsilateral ear tends to perform at or near 100%, implying that no residual competition, either phonetic or acoustic, exists between channels at the central analyzer. The impact of this observation on the nature of the dichotic listening task and the lag effect will be discussed. [ABSTRACT FROM AUTHOR]