Visual encoding, consolidation, and retrieval in amyotrophic lateral sclerosis: executive function as a mediator, and predictor of performance.

OBJECTIVE: This study aimed to illustrate the variation of non-executive cognitive processes, i.e. visual memory, considering executive dysfunction in amyotrophic lateral sclerosis (ALS).

METHODS: Patients with ALS (n = 203), and matched healthy controls (n = 117) completed a battery of neuropsychological tests. Sub-stratification was based on whether cognitive assessment detected no cognitive abnormalities (NCA: n = 117), multiple executive cognitive deficits (ALS-Exec; n = 56), or a comorbid frontotemporal dementia process (ALS-FTD; n = 30). The Rey-Osterrieth Complex Figure Test (ROCFT) was the main dependent variable for visual memory in this study.

RESULTS: Patients and controls significantly differed on the Copy trial (p < 0.0001: ω2 = 0.317) immediate recall (p < 0.0001: ω2 = 0.272) and delayed recall (p < 0.0001: ω2 = 0.308) of the ROCFT. Sub-stratification based on executive dysfunction revealed an association with greater executive dysfunction and lower ROCFT performance. Regression analysis predicted that premorbid IQ, executive function, and demographics predict performance on the ROCFT delayed recall trial (R2  = 0.833).

CONCLUSIONS: These findings illustrate that patients without executive dysfunction do not show visual memory impairments within this cohort; that patients with executive dysfunction have poorer performance on visual memory tasks; and that the severity of executive dysfunction, as per cognitive categorisation, is related to increased visual memory impairment as tested with the ROCFT.