Central auditory processing in an adult with congenital absence of left temporal lobe

A young adult subject with congenital absence of the left temporal lobe received extensive behavioral and electrophysiologic tests to identify deficits in central auditory processing. Tests included the dichotic digits, staggered spondaic words (SSW), synthetic sentence identification with ipsilateral (SSI-ICM) and contralateral (SSI-CCM) competing messages, pitch pattern, and duration pattern measures. Additional special tests included the precedence effect in sound localization, measurement of frequency difference limens for short (5 msec) and long (200 msec) duration tones, and the P300 event-related potential. The subject's performance on all measures was well within normal limits. These findings provide important new evidence that reinforces the belief of neuroscientists that the developing nervous system exhibits a remarkable degree of functional plasticity.