Time perception following unilateral amobarbital injection in patients with temporal lobe epilepsy

Estimates of elapsed time were obtained from 53 patients with unilateral temporal lobe epilepsy (Left TLE = 27; Right TLE = 26) following Wada (intracarotid amobarbital) assessment. After resolution of drug effects, patients were asked to estimate how much time had passed since amobarbital administration. Estimates were also obtained from 24 healthy control subjects using the same cognitive tasks over a similar time frame. Elapsed time was significantly underestimated by both left and right TLE groups following right hemisphere injection. In addition, there was an interaction effect involving patient group, side of injection, and sequence of injection. Left TLE patients, consistent with normal controls, made more accurate time estimates when they could anticipate the estimation task following the second amobarbital administration. More accurate time estimates, however, occurred only when left hemisphere injection was second in sequence. In contrast, right TLE patients did not improve regardless of the order of injection. These results suggest that right hemisphere function plays a critical role in the accuracy of time estimations of intermediate temporal duration and that interhemispheric interaction may be required to make accurate retrospective temporal judgments. These findings are discussed in the context of the growing evidence for a right-hemispheric attentional network.