Stimulus-related modulation in the 1/f spectral slope suggests an impaired inhibition of irrelevant information in people with multiple sclerosis

Abstract

AbstractBackgroundMultiple sclerosis (MS) is an inflammatory and neurodegenerative disease characterized by neuronal and synaptic loss, resulting in an imbalance of excitatory and inhibitory synaptic transmission. MS leads to cognitive impairment such as reduced information processing speed and impaired working memory (WM). Recent studies have suggested that the 1/f slope of EEG/MEG power spectra can be associated with the excitation/inhibition (E/I) balance. A normal E/I balance is crucial for normal information processing and working memory.MethodsWe analyzed magnetoencephalographic (MEG) recordings of 38 healthy control subjects and 79 people with multiple sclerosis (pwMS) while performing an n-back working task. We computed and compared the steepness of the 1/f spectral slope through the FOOOF algorithm in the time windows [-1 0] and [0 1] s peristimulus time for both target and distractor stimulus for each brain parcel and for different working memory loads (0-back, 1-back, 2-back).ResultsThe spectral slope was significantly steeper after the stimulus onset and was correlated with reaction time. We also observed a steeper 1/f slope after distractor stimuli in healthy subjects compared to pwMS. Finally, we observed significant correlations between the 1/f spectral slope modulation and visuospatial working memory functioning in both healthy subjects and pwMS.ConclusionOur findings are consistent with an increased inhibition following stimulus onset. In pwMS, this increase is reduced, suggesting dysfunctional inhibition of irrelevant information. Finally, this impaired modulation is significantly associated with a pencil-paper test of visuospatial working memory.HighlightsThe flatter 1/f slope after distractor stimuli in people with multiple sclerosis (pwMS) compared to healthy subjects suggests a less pronounced inhibition of irrelevant information in pwMS.The significantly flatter 1/f slope was observed in the left inferior dorsal prefrontal cortex of pwMS in both 1-back and 2-back conditions. This particular brain parcel is known for its key role in motor planning, and the maintenance of sustained attention and working memory and executive functions.A steeper 1/f slope after target and distractor stimuli suggests an increase in inhibition following stimulus onset in both healthy controls (HCs) and people with MS (pwMS).The 1/f slope modulation correlates with visuospatial working memory performance.