Klinische Neurophysiologie 2012; 43 - V086
DOI: 10.1055/s-0032-1301482

Electrophysiological correlates of working memory performance in the course of amyotrophic lateral sclerosis

N Naue 1, J Machts 1, A Becke 2, JM Hopf 2, S Petri 3, K Kollewe 3, R Dengler 3, N Müller 1, HJ Heinze 2, S Vielhaber 2
  • 1German Center for Neurodegenerative Diseases, Magdeburg
  • 2Otto-von-Guericke University, Department of Neurology, Magdeburg
  • 3Hannover Medical School, Department of Neurology, Hannover

Aims: Amyotrophic lateral sclerosis (ALS) is primarily a motor system disease. However, despite the motor neuron degeneration, these patients also develop cognitive impairments including executive dysfunctions, in particular working memory and fluency. We used serial recordings of event-related brain potentials (ERPs) to provide the first assessment of longitudinal changes in working memory in patients with ALS compared to controls.

Methods: For that purpose we examined ALS patients in a visual working memory task while the electroencephalogram (EEG) was measured. To investigate the progression of ALS related cognitive dysfunctions the patients performed the task two times with a delay of 3 months. To assess working memory performance we adapted an established working memory paradigm introduced by Vogel et al. (2004) and analyzed the Contralateral Delayed Activity (CDA). This electrophysiological component reflects the encoding and maintenance of items in visual memory and is strongly modulated by the number of objects being held in visual memory. Additionally, the data were compared to a matched control group of healthy participants.

Results: On the behavioural level, patients working memory performance showed no difference between the two acquisition times. However, electrophysiological data indicate a systematic modulation of event-related potentials in the course of ALS. Thus electrophysiological data suggest an alteration in working memory, augmenting the detection power in neuropsychology of prefrontal dysfunction.

Conclusions: Behavioural data indicate that cognitive impairment in ALS patients is stable during a period of 3 months. Notwithstanding, electrophysiological data point to altered neural processing underlying working memory performance, indicating changes in cognitive strategies applied. Additional study is needed to establish whether the changes in neurophysiological markers of prefrontal dysfunction are related to different subtypes of ALS.

Literatur: Vogel, E.K., Machizawa, M.G. (2004). Neural activity predicts individual differences in visual working memory capacity. Nature, 428, 748-751.