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.
Highlights
IntroductionThe processing of external salient stimuli (i.e., exteroceptive processing) is critical for responding and adapting to the environment
The processing of external salient stimuli is critical for responding and adapting to the environment
There were no significant differences in age, gender, or ethnicity between the cannabis users and non-using controls; the controls as a group were older compared to the users
Summary
The processing of external salient stimuli (i.e., exteroceptive processing) is critical for responding and adapting to the environment. The posterior cingulate cortex (PCC) and precuneus have been implicated in exteroceptive processing (Fransson, 2005; Lou et al, 2010; Luber et al, 2012) and exhibit activation that is correlated with the default mode network (Fox et al, 2005; Raichle, 2011; Utevsky et al, 2014). This correlation with the default mode network, a network of brain regions that exhibits activation during resting state and deactivation when engaged in a task, is thought to be critical for continuously monitoring the environment for self-relevant stimuli.
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