CHRONIC STIMULATION OF THE LEFT VAGUS NERVE - COGNITIVE MOTOR EFFECTS

Background: Early studies of cognitive motor control have shown defici ts in complex reaction time tests of epileptic subjects, The purpose o f this efficacy study was to determine whether chronic (28 months) sti mulation of the left vagus nerve (VNS) to control seizures increased t hese deficits in 6 epileptic subjects with intractable complex partial seizures, it Methods: Subjects were assessed for simple reaction time , Test A, and subsequent Tests B and C which involved more complex cog nitive strategies. Tests were done pre-operatively (S1) and at interva ls, 6-8 weeks (S2-S3), and at 6 month intervals (S4-S6) over a 28 mont h period. Data were collected and collated on an Apple II E computer ( Apple, Cupertino CA. U.S.A.) and on electronic switch pad, Data were a nalyzed using a repeated measures analysis of covariance technique wit h 2 within subject factors, day, and time of day. Results: 2/11 cognit ive measures showed a statistically significant difference. Error rate associated with Test A (simple reaction time) significantly decreased for the factor of day (repeated visits) p = .01. For Test C, error ra tes decreased in the afternoon (p = .03), This test involved the subje cts ability to respond quickly to one signal while simultaneously igno ring a second signal, Data analysis of the covariate showed that the e ffects of VNS are weak in comparison to baseline differences and the f requency of nerve stimulation negatively predicts the number of wrong errors, High frequency stimulation results showed fewer errors than lo w frequency stimulation T = -2.31, p = .03, Conclusion: Chronic stimul ation of the left vagus nerve to control seizure activity does nor imp air cognitive motor control.