Working memory in amyotrophic lateral sclerosis: auditory event-related potentials and neuropsychological evidence

Aim of this study is to investigate working memory functions in nondemented patients with amyotrophic lateral sclerosis (ALS) using neuropsychological testing and auditory event-related potentials. Twenty-four patients with ALS and 17 age- and education-matched controls underwent a comprehensive neuropsychological assessment, with particular emphasis on working memory functions. Event-related potentials were assessed with an active auditory oddball paradigm. In a subsample (67%) of patients with ALS, the neuropsychological assessment revealed impaired performance on working memory tests (semantic and letter verbal fluency, modified card sorting test, trail making test, digit span, Corsi blocks tapping test, and prose memory). The analysis of event-related potentials showed a significant delay of the N100, P200, and N200 latency in ALS compared with controls. Correlation analysis showed a relation between clinical parameters (disease duration and functional rating scale) and neuropsychological test results (letter fluency and trail making test) and between disease duration and P300 amplitude. The neuropsychological and event-related potentials profile of patients with ALS at an average is consistent with a mild dysfunction of the central executive component of working memory. In conclusion, the results support previously published reports that indicate the involvement of the extramotor functions in a significant subsample of ALS.