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62 COVERT VISUAL ATTENTION AND MOVEMENT PREPARATION IMPAIRMENTS IN EPILEPSY.
  1. E. K. St. Louis,
  2. J. Dennhardt,
  3. S. J. Luck
  1. University of Iowa, Iowa City, IA; Davis, CA.

Abstract

Background/Rationale Identification of subtle cognitive impairments that may adversely affect quality of life in epilepsy is often difficult. The N2pc and lateralized readiness potential (LRP) event-related potential (ERP) paradigms are capable of detecting and quantifying covert, real-time neural processing with exquisite temporal sensitivity. We hypothesized that the N2pc and LRP are delayed in epilepsy.

Methods Ten epilepsy subjects (4 mesial temporal, 1 extratemporal, 3 idiopathic generalized, and 2 new onset, each receiving one to three AEDs) and 20 controls underwent ERP recording from standard 10-20 electrode sites while performing a feature-conjunction visual-search task. Data analysis compared ERP waves from equivalent channels ipsilateral and contralateral to the target using Student's t-test, ANOVA, and jackknifing data resampling procedures.

Results N2pc peak latency was significantly delayed in epilepsy subjects by approximately 35 msec (p < .016; data shown in the Table and Figure). LRP peak latency was also significantly delayed in epilepsy subjects. P1, N2, and P3 latencies did not differ between epilepsy and control subjects.

Conclusions There is a significant delay in visual attentional processing in epilepsy subjects and additional impairment of movement preparation but not categorization. Although subtle and covert to bedside detection, these additive delays in the first half-second of neural processing could underlie subjectively impaired cognitive functioning in epilepsy patients and substantially impact their performance during demanding psychomotor tasks requiring rapid reaction time, such as driving. Future research will focus on determining the causes of these delays in cognitive processing, including epilepsy syndrome, brain lesions, and antiepileptic drugs.

Delayed N2pc and LRP ERP Responses in Epilepsy

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