Abstract
PURPOSE: This preliminary study aimed to investigate whether the pupil size reflects cognitive load in patients with amyotrophic lateral sclerosis (ALS). METHODS: Pupil activity was monitored in three patients with ALS and a group of healthy control participants (n = 16) while performing three tasks: a forward span task, a backward span task, and a control task involving counting aloud. These tasks were designed to impose increasing cognitive demands, with the backward span task being the most challenging. RESULTS: Analysis revealed no significant difference in pupil size between patients with ALS and controls for the forward or backward spans or the control condition. Both groups demonstrated a consistent pattern of increased pupil size during the backward span task compared to the forward span task, and during the forward span task compared to the control condition. CONCLUSION: These findings suggest that pupil dilation reflects task-related cognitive load similarly in ALS patients and healthy controls. This supports the use of pupillometry as a non-invasive and sensitive marker of cognitive processing in ALS.