Attention deficit in multiple sclerosis: An electrophysiological investigation using Posner's paradigm

Description

Multiple sclerosis (MS) is frequently associated with fronto-subcortical dysfunction. Nevertheless; the specific basis for this pattern of cognitive dysfunction is still not clear in this disease. The current study aimed at further tracking the attention deficit in MS investigating 10 patients with remittent MS and 10 age-matched healthy volunteers. To study endogenous and exogenous components of attention allocation, we measured reaction times (RTs) and recorded event-related potentials (ERPs) at 26 electrode sites in a visuospatial attention paradigm (Posner, 1980). Par- ticipants performed a detection task with two types of cues, peripheral (a square) and central (an arrow), which, respectively, involved exogenous (automatic) and endogenous (controlled) attention processes. Half of the trials were valid (i.e., the cue oriented the attention to the correct target location) and half of them were not valid (i.e., the cue oriented the attention to the opposite side). RT analyses showed characteristic validity effects for both peripheral and central cueing in control subjects with a right hemispheric advantage. In contrast, MS patients demonstrated a RT validity effect only in the peripheral cueing. Electrophysiological data showed longer N1 and P2 latencies in MS patients compared to controls arguing for an early dysfunction of information processing at perceptive stages with a reduction of N1 amplitude at frontal sites in favour of an early modification of attention modulation. These results suggest that MS might modify only the endogenous component of attention allocation (i.e., controlled attention processes). Our investigation also underlines the usefulness of ERP recording to detect early cognitive disorders in MS.

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