Effects of Repetitive Transcranial Magnetic Stimulation on the Connectivity of the Resting-State Triple Network in Cannabis Users
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A large number of studies have reported the association between pathological neural diseases (e.g., addicted disorders) and abnormal interactions in a large-scale brain network which is called the triple network. Cannabis users have shown dysfunctional interactions in the triple network during resting state (RS), which has been related to problematic symptoms of cannabis use. Among diverse tools, non-invasive repetitive transcranial magnetic stimulation (rTMS) has been introduced as an effective tool to moderate aberrant activity in the triple network. The posterior cingulate cortex (PCC) and precuneus are important hubs in the default mode network (DMN) and have cannabinoid receptors targeted by delta 9 tetrahydrocannabinol (THC) which is the main component of cannabis. This led us to test whether neuromodulation of these regions may moderate dysfunctional interactions between the areas of the triple network at rest. To that end, we collected electroencephalographic (EEG) recordings during RS after 10 Hz (high frequency, HF) and 1 Hz rTMS (low frequency, LF) in 12 cannabis users and 11 non-cannabis users. Using the exact Low-Resolution Electromagnetic Tomography (eLORETA) software, we examined connectivity strength in the triple network with resting-state EEG recordings. The results showed that HF rTMS to the PCC and precuneus has increased the delta connectivity following the LF rTMS between DMN and central executive network (CEN) in cannabis users, specifically between the PCC and left dorsolateral prefrontal cortex (dlPFC). In contrast, no effects of HF rTMS were observed in non-cannabis users. To sum up, our results present that HF rTMS to the PCC and precuneus can effectively modulate a partial connectivity (DMN-CEN) of large-scale network in cannabis users.