Abstracts

Little previous research has analyzed the critical cognitive domain of attention in epilepsy. The event-related potentials (ERP) technique is capable of detecting and quantifying covert cognitive impairments with exquisite temporal sensitivity. We hypothesized that the N2PC response, an ERP measure of visual attention, would be delayed in epilepsy., Following IRB approval, we recorded the N2pc from 20 control and 10 (4 mesial temporal, 1 extratemporal, 3 idiopathic generalized, and 2 new onset) epilepsy subjects. Epilepsy subjects were receiving 1-3 AEDs. Subjects detected targets in either the right or left visual field during a feature-conjunction visual-search task. EEG recordings were obtained from F3, F4, C3, C4, P3, P4, O1, O2, OL, OR, T5 and T6. Data analysis compared ERP waves from equivalent channels ipsilateral and contralateral to the target. Fractional peak latency (when amplitude had reached 50% of peak) was determined for all subjects., Epilepsy subjects showed significantly delayed N2pc responses in occipital regions compared to controls (data in table). Channels O1/2 delays were 26.8 ms (t= -2.07, p=0.01) and channels OL/R delays were 25.0ms (t= -1.77 , p=0.04). The figure depicts N2pc difference waveforms for epilepsy (dotted curve) and control (solid) subjects.[table1][figure1], Visual attentional processing is significantly delayed in epilepsy, by approximately 25 ms. During visual search, attention normally shifts every 25-100 ms, so a delay of 25 ms for each shift of attention could cause substantial downstream problems under natural viewing conditions, particularly during demanding psychomotor tasks requiring rapid cognitive processing, reaction time, and decision making, such as driving. Future research will focus on parsing apart the causes of this delay, including the epilepsy syndrome, brain lesions associated with epilepsy, and antiepileptic drugs., (Supported by Nathan R. and Beth L. Tross Epilepsy and Cognitive Neuroscience Research Fund, University of Iowa Department of Neurology.)