Abstract
RationaleAn acute challenge with delta-9-tetrahydrocannabinol (THC) can induce psychotic symptoms including delusions. High electroencephalography (EEG) frequencies, above 20 Hz, have previously been implicated in psychosis and schizophrenia.ObjectivesThe objective of this study is to determine the effect of intravenous THC compared to placebo on high-frequency EEG.MethodsA double-blind cross-over study design was used. In the resting state, the high-beta to low-gamma magnitude (21–45 Hz) was investigated (n = 13 pairs + 4 THC only). Also, the event-related synchronisation (ERS) of motor-associated high gamma was studied using a self-paced button press task (n = 15).ResultsIn the resting state, there was a significant condition × frequency interaction (p = 0.00017), consisting of a shift towards higher frequencies under THC conditions (reduced high beta [21–27 Hz] and increased low gamma [27–45 Hz]). There was also a condition × frequency × location interaction (p = 0.006), such that the reduction in 21–27-Hz magnitude tended to be more prominent in anterior regions, whilst posterior areas tended to show greater 27–45-Hz increases. This effect was correlated with positive symptoms, as assessed on the Positive and Negative Syndrome Scale (PANSS) (r = 0.429, p = 0.042). In the motor task, there was a main effect of THC to increase 65–130-Hz ERS (p = 0.035) over contra-lateral sensorimotor areas, which was driven by increased magnitude in the higher, 85–130-Hz band (p = 0.02) and not the 65–85-Hz band.ConclusionsThe THC-induced shift to faster gamma oscillations may represent an over-activation of the cortex, possibly related to saliency misattribution in the delusional state.Electronic supplementary materialThe online version of this article (doi:10.1007/s00213-014-3684-1) contains supplementary material, which is available to authorized users.
Highlights
There is evidence that the chronic use of Δ9-tetrahydrocannabinol (THC) is a risk factor for schizophrenia (Andreasson et al 1987; Arseneault et al 2002; Henquet et al 2005; Moore et al 2007)
The overall mean 27–45-Hz amplitude was divided by the 21–27-Hz amplitude, but this first ratio was not correlated with Positive and Negative Syndrome Scale (PANSS) positive symptom scores
To take into account the location effect as well as the frequency effect, the posterior 27–45-Hz amplitude was divided by the anterior 21–27-Hz amplitude (Table 1). This ratio did show a positive association with PANSS positive symptom scores (r=0.429, p=0.021) in the THC condition, which was still significant after correction for multiple comparisons (p=0.042)
Summary
There is evidence that the chronic use of Δ9-tetrahydrocannabinol (THC) is a risk factor for schizophrenia (Andreasson et al 1987; Arseneault et al 2002; Henquet et al 2005; Moore et al 2007). In chronic cannabis users, Auditory Steady-State Responses (ASSRs) to 40-Hz click trains have been found to be reduced (Skosnik et al 2012), demonstrating an impairment in the capacity of neural circuits to support gamma band oscillations. These changes are similar to reductions in event-related potentials and phase locking observed in schizophrenia (Kwon et al 1999; Bramon et al 2005; Spencer et al 2008; Hall et al 2011), there have been contradictory results (Spencer and Ghorashi 2014). Since aberrant salience attribution is thought to underlie delusions (Kapur 2003) and a higher peak frequency of gamma may reflect the saliency of a stimulus (van Pelt and Fries 2013), the frequency distribution of high-frequency oscillations may be important in psychosis, but this has not yet been investigated
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
