Recognition memory deficits in amyotrophic lateral sclerosis assessed with event-related brain potentials

Objectives - Amyotrophic lateral sclerosis (ALS) has been shown to cause neuropsychological deficits. The present investigation sought to delineate memory deficits by recording cognitive event-related potentials (ERPs). Subjects and methods - Eight ALS patients and 8 matched controls were subjected to a 2-phase recognition memory test. During the first phase words were presented consecutively on a video-screen with one-third of the words being repeated. The subject had to press buttons according to whether a word had been repeated or not. During the second phase (delay 1 h) a second list containing 33% old items from phase 1 and 66% new words was shown with an old/new decision required. Results - ALS patients showed less accurate recognition in the second phase. The ERPs of the controls showed a reliable difference between old and new items in both phases. This difference was nearly absent in the patients in both phases. Conclusion - The ERP pattern suggests abnormal memory processes in ALS. The results are compared with data from similar experiments in Huntington's and Alzheimer's disease and are interpreted in terms of an encoding deficit in ALS.