Testing the role of the posterior cingulate cortex in processing salient stimuli in cannabis users: an rTMS study

Abstract

The posterior cingulate cortex (PCC) and precuneus are hubs in the default mode network and play a role in processing external salient stimuli. Accordingly, activation in these regions has been associated with response to salient stimuli using drug cue‐reactivity paradigms in substance using populations. These studies suggest that the PCC and precuneus may underlie deficits in processing salient stimuli that contribute toward the development of substance use disorders. The goal of this study was to directly test this hypothesis using repetitive transcranial magnetic stimulation (rTMS). Using a double‐blind, placebo‐controlled design, we used rTMS to target the PCC and precuneus with a double‐cone coil at 10 Hz (high frequency) and 1 Hz (low frequency) in 10 adult cannabis users and 10 age‐ and sex‐matched non‐using controls. Electroencephalography data were collected before and after rTMS during a modified oddball paradigm with neutral, oddball, self‐relevant, and cannabis‐related stimuli. Cannabis users exhibited increased amplitude in P3 and faster latencies in the P3, N2, and P2 components in response to self‐relevant stimuli compared to controls during baseline that normalized after rTMS. These results suggest that cannabis users exhibited heightened salience to external self‐relevant stimuli that were modulated after rTMS. PCC dysfunction in cannabis users may be related to abnormalities in processing salient stimuli, such those during cue‐reactivity, and provides a potential target for cannabis use disorder intervention.

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“…Based on these observations a recent study employed transcranial stimulation (TMS) to this region during cueinduced reactivity in substance addiction and demonstrated that down-regulation of this region normalized exaggerated self-referential attribution in cannabis-dependent subjects. 44 In the context of these previous findings the convergent cross sectional is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint…”

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“…engaging different brain regions in these different subgroups). In another double‐blind, placebo‐controlled, cross‐over design, high‐frequency repetitive transcranial magnetic stimulation (rTMS) to the posterior cingulate cortex and cuneus showed normalization of the processing of self‐relevant stimuli (assessed using event‐related potential P3 amplitudes and P3, N2 and P2 latencies) in cannabis users as compared with non‐users (Prashad et al ., ). Thus, in addition to pharmacological approaches in combination with magnetic resonance imaging to measure outcomes, brain stimulation and EEG recordings expand the toolbox available to clinicians in treating addiction.…”

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