The effect of chronic cannabinoids on broadband EEG neural oscillations in humans.

Animal and cellular work has shown that central cannabinoid-1 receptors modulate neural oscillations in the gamma range (40 Hz), which may be important for normal perceptual and cognitive processes. In order to assess the effect of cannabinoids on broadband-frequency neural oscillations in humans, the current study examined the effect of chronic cannabis use on auditory steady-state responses (ASSRs) utilizing electroencephalography (EEG). Passive ASSRs were assessed using varying rates of binaural stimulation (auditory click-trains; 10-50 Hz in increments of 5 Hz; 80 dB SPL) in carefully screened cannabis users and controls. Chronic cannabis users (n=22; 12 h abstinence before study; positive 11-nor-9-carboxy-delta-9-tetrahydrocannabinol urine levels) and cannabis naïve controls (n=24) were evaluated. Time X frequency analyses on EEG data were performed using Fourier-based mean trial power (MTP) and phase-locking (inter-trial coherence; ITC). Transient ERPs to stimulus onset (auditory N100 components) were also evaluated. As predicted, a decrease in spectral power (MTP) at 40 Hz was observed in the cannabis group (p<0.018). No effects on phase-locking (ITC) or the N100 were observed. Further, within the cannabis group, lower 40 Hz power correlated with an earlier age of onset of cannabis use (p<0.04). These data suggest that chronic exposure to exogenous cannabinoids can alter the ability to generate neural oscillations, particularly in the gamma range. This is consistent with preclinical animal and cellular data, which may have implications for understanding the short- and long-term psychopharmacological effects of cannabis.