AUDITORY SPEECH PROCESSING IN THE LEFT TEMPORAL-LOBE - AN ELECTRICAL INTERFERENCE STUDY

Auditory syllable discrimination, identification, and comprehension we re investigated by direct cortical electrical interference in three pa tients with indwelling subdural electrode arrays. Without electrical i nterference, patients performed similarly to matched normal subjects. With electrical interference, selective deficits were observed in the posterior superior temporal (PST) lobes of all three patients. At spec ific PST sites, only comprehension was impaired, while at proximal sit es comprehension and identification were impaired, but discrimination remained intact. At a single PST site, all three auditory speech funct ions were impaired. These findings suggest that lower-level auditory s peech functions can operate independent of higher-level processes, as claimed by traditional hierarchical models. However, analysis of discr imination errors revealed lexical-semantic and phonological effects, s uggesting that higher-bevel functions also influence lower-level proce ssing. These data can be explained by a bidirectional processing model , with differentially weighted connections. (C) 1995 Academic Press, I nc.