Substance-related visual cues alter sensory gating in adults who regularly use methamphetamine.

BACKGROUND: Methamphetamine is a highly addictive psychostimulant associated with widespread neurobiological alterations. While the acute and chronic effects on the brain have been extensively studied in animal models, far less is known about its impact on the human brain, particularly in the context of inhibitory processing. METHODS: Seventy-two participants (35 who regularly use methamphetamine) completed a paired-pulse somatosensory gating paradigm during magnetoencephalography (MEG). Immediately before the first stimulation of each trial, participants viewed either a substance-related or neutral image. The resulting responses were imaged, and time series were extracted from the peak voxel in the whole-brain maps, which was centered on the contralateral postcentral gyrus. Gating ratios (Stimulation 2/Stimulation 1) were subjected to a linear mixed-effect model, and spontaneous activity in the same voxel was assessed. RESULTS: We found a significant group-by-condition interaction and a main effect of group, with the latter indicating that controls had significantly stronger gating across both task conditions compared to the methamphetamine group. Interestingly, the interaction revealed that only those in the methamphetamine group exhibited weaker gating in the substance-cue compared to the neutral image condition. Furthermore, gating indices were predictive of processing speed above and beyond the effect of group, while spontaneous gamma during the baseline was elevated in the methamphetamine group compared to controls. CONCLUSIONS: Adults who use methamphetamine exhibit altered gating responses and elevated spontaneous gamma activity in the somatosensory cortices, likely reflecting disruptions in GABAergic circuitry. Substance-related cues accentuated gating deficits, suggesting that cue reactivity may compromise sensory inhibition in this population.