DIFFERENTIAL RESPONSE CHARACTERISTICS IN NONEPILEPTIC AND EPILEPTIC SEIZURE PATIENTS ON A TEST OF VERBAL-LEARNING AND MEMORY

Investigators have found it difficult to separate patients with nonepi leptic seizures (NES) from those with true epileptic seizures (ES) usi ng quantitative measures of neuropsychological test performance. We ex amined qualitative response characteristics on the California Verbal L earning Test of 41 patients undergoing continuous video/audio-EEG moni toring in an effort to distinguish these patient groups (12 patients w ith left temporal [LT] foci, 11 with right temporal [RT] foci, and 18 with NES). NES patients explicitly recognized fewer target words compa red with ES patients. In addition, NES patients rarely made false-posi tive errors, which resulted in failure to endorse a significant number of items on the recognition list. This response tendency is called a negative response bias. In contrast, LT patients endorsed a high numbe r of items on the recognition test, which resulted in a positive respo nse bias. RT patients demonstrated no consistent response tendency. In our sample, a negative response bias index (ie, a cutoff score <0) sh owed a sensitivity of 61% and a specificity of 91%. We propose that fa ilure to explicitly recognize words following repeated exposure may re flect aspects of psychological denial in NES patients. Response bias i ndices may thus help identify patients with NES and may begin to expla in the psychological mechanisms underlying this complex disorder.