Abstracts

Rationale: Temporal lobe epilepsy (TLE) is associated with a number of specific cognitive deficits, best described in the domains of memory and language. We have been studying the effect of TLE on interictal perceptual function, using a battery of quantitative, low level, psychophysical perceptual tasks. Here we report final results of tests in the auditory domain. Methods: Subjects included 33 adult patients with medically uncontrolled unilateral TLE and 24 community controls of similar age and education. Auditory stimuli were presented separately to each ear in the TLE subjects and to the right ear in the controls. Each trial consisted of a three-alternative forced-choice paradigm, and the staircase method was used to converge on 70.7% correct response. Tasks included amplitude discrimination and frequency (pitch) discrimination performed at stimulus durations of both 200 and 20 msec. Subjects completed each task 3 times, and the psychophysical threshold (at each ear) was taken as the mean of the three threshold values. Results: Performance of TLE subjects was considerably worse than that of controls in the frequency discrimination tasks, but nearly identical to that of controls in the amplitude discrimination tasks. However, none of these differences reached statistical significance. Performance of TLE subjects also did not differ significantly between the ears ipsilateral and contralateral to seizure onset. Finally, there was no change in performance among 6 TLE subjects tested before, and at least 6 months after temporal lobectomy. Conclusions: These data suggest that TLE affects auditory frequency and amplitude discrimination differentially. However, as there were no statistically significant between group performance differences, the impact of TLE on these low-level auditory discrimination tasks appears to be minor, despite the central role of the temporal lobe in auditory processing. The fact that performance did not worsen in the 6 patients who underwent anteromesial temporal lobectomy is encouraging, and suggests that this surgery does not impair the perceptual circuitry subserving these auditory functions, i.e. pitch and loudness discrimination. (supported by NINDS K23 NS46347 to ACG)