Alterations in Electroencephalography Theta as Candidate Biomarkers of Acute Cannabis Intoxication

Identifying EEG markers related to acute cannabis consumption: A systematic review

BACKGROUND/RATIONALE

Electroencephalography (EEG) has potential to provide a sensitive measure of the acute neurophysiological response to cannabis administration. As delta-9-tetrahydrocannabinol (THC; the psychoactive constituent of cannabis) can induce transient neurocognitive impairments that differ as a function of tolerance and dose, understanding the neural profile related to intoxication would be of great benefit in the wake of increasing recreational and medicinal use. Accordingly, the present systematic review examined the current research literature related to acute cannabis administration and EEG measures.

METHODS

Peer-reviewed articles published from 2000 were assessed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies that administered non-synthetic cannabis, containing THC (orally or inhaled) and reported differences in EEG outcomes within the acute time frame (<6 hours post-administration) as compared to baseline or placebo, were eligible for inclusion.

RESULTS/DISCUSSION

A total of 16 studies were eligible for inclusion, of which 11 reported differences in the amplitude/latency of event-related potentials (ERPs) and 9 reported changes in frequency band power. Of the ERPs, the P3 was identified as a potential indicator of recent cannabis consumption, as demonstrated by decreased P3 amplitude across various doses (generally exhibiting small-to-moderate magnitude effects where effect sizes were reported). Oscillatory activity in the theta frequency band power range (typically 4-7 Hz) was impacted following cannabis administration, with some support for a dose-dependent change in power. The present results highlight the potential utility of some EEG measures as markers of recent cannabis consumption, although great heterogeneity in participant characteristics and reported data limits conclusions from these results. It is also evident that EEG changes in highly tolerant user groups (such as those who use cannabis medicinally), require further exploration.

Effect of cannabis on brain activity in males: Quantitative electroencephalography and its relationship with duration, dosage, and age of onset

OBJECTIVE

Brain function changes as a result of cannabis use. This study examined the brain activity of cannabis users compared to a healthy group and nicotine smokers, focusing on the age of onset, duration of use, and dosage.

METHOD

Demographic and quantitative electroencephalography (QEEG) data of 15 healthy individuals, 20 patients with chronic cannabis use, and 15 nicotine smokers were collected and recorded during the eyes-closed and eyes-open conditions in the resting state. The data were analyzed using MATLAB software and the EEGLAB toolbox.

RESULTS

In the eyes-closed condition, cannabis users exhibited significantly elevated relative theta band power in widespread brain regions compared to both the healthy group and nicotine smokers. They showed decreased relative power in the beta and gamma bands in the parietal and occipital regions when compared to nicotine smokers. In the eyes-open condition, cannabis users displayed increased relative theta band power in widespread brain regions relative to both groups. Additionally, lower relative power in the beta and gamma bands was observed in cannabis users compared to the healthy group in the frontal region, as well as in various brain regions compared to nicotine smokers. A significant relationship was identified between gamma-band power, age of onset, and dosage of cannabis use.

CONCLUSION

These findings suggest that cannabis use leads to changes in brain wave patterns during the resting state, which may be linked to cognitive impairments affecting functions. Understanding these associations is essential for developing effective intervention programs aimed at mitigating cognitive deficits related to cannabis use.

EEG and ERP biosignatures of mild cognitive impairment for longitudinal monitoring of early cognitive decline in Alzheimer's disease

Cognitive decline in Alzheimer's disease is associated with electroencephalographic (EEG) biosignatures even at early stages of mild cognitive impairment (MCI). The aim of this work is to provide a unified measure of cognitive decline by aggregating biosignatures from multiple EEG modalities and to evaluate repeatability of the composite measure at an individual level. These modalities included resting state EEG (eyes-closed) and two event-related potential (ERP) tasks on visual memory and attention. We compared individuals with MCI (n = 38) to age-matched healthy controls HC (n = 44). In resting state EEG, the MCI group exhibited higher power in Theta (3-7Hz) and lower power in Beta (13-20Hz) frequency bands. In both ERP tasks, the MCI group exhibited reduced ERP late positive potential (LPP), delayed ERP early component latency, slower reaction time, and decreased response accuracy. Cluster-based permutation analysis revealed significant clusters of difference between the MCI and HC groups in the frequency-channel and time-channel spaces. Cluster-based measures and performance measures (12 biosignatures in total) were selected as predictors of MCI. We trained a support vector machine (SVM) classifier achieving AUC = 0.89, accuracy = 77% in cross-validation using all data. Split-data validation resulted in (AUC = 0.87, accuracy = 76%) and (AUC = 0.75, accuracy = 70%) on testing data at baseline and follow-up visits, respectively. Classification scores at baseline and follow-up visits were correlated (r = 0.72, p<0.001, ICC = 0.84), supporting test-retest reliability of EEG biosignature. These results support the utility of EEG/ERP for prognostic testing, repeated assessments, and tracking potential treatment outcomes in the limited duration of clinical trials.

Decomposing the late positive potential to cannabis cues in regular cannabis users: A temporal-spatial principal component analysis

Cannabis use disorder (CUD) is increasing in the United States, yet, specific neural mechanisms of CUD are not well understood. Disordered substance use is characterized by heightened drug cue incentive salience, which can be measured using the late positive potential (LPP), an event-related potential (ERP) evoked by motivationally significant stimuli. The drug cue LPP is typically quantified by averaging the slow wave's scalp-recorded amplitude across its entire time course, which may obscure distinct underlying factors with differential predictive validity; however, no study to date has examined this possibility. In a sample of 105 cannabis users, temporo-spatial Principal Component Analysis was used to decompose cannabis cue modulation of the LPP into its underlying factors. Acute stress was also inducted to allow for identification of specific cannabis LPP factors sensitive to stress. Factor associations with CUD severity were also explored. Eight factors showed significantly increased amplitudes to cannabis images relative to neutral images. These factors spanned early (~372 ms), middle (~824 ms), and late (>1000 ms) windows across frontal, central, and parietal-occipital sites. CUD phenotype individual differences were primarily associated with frontal, middle/late latency factor amplitudes. Acute stress effects were limited to one early central and one late frontal factor. Taken together, results suggest that the cannabis LPP can be decomposed into distinct, temporal-spatial factors with differential responsivity to acute stress and CUD phenotype variability. Future individual difference studies examining drug cue modulation of the LPP should consider (1) frontalcentral poolings in addition to conventional central-parietal sites, and (2) later LPP time windows.

The Relationship Between Cannabinoids and Neural Oscillations: How Cannabis Disrupts Sensation, Perception, and Cognition

Disruptions in neural oscillations are believed to be one critical mechanism by which cannabinoids, such as delta-9-tetrahyrdrocannabinol (THC; the primary psychoactive constituent of cannabis), perturbs brain function. Here we briefly review the role of synchronized neural activity, particularly in the gamma (30-80 Hz) and theta (4-7 Hz) frequency range, in sensation, perception, and cognition. This is followed by a review of clinical studies utilizing electroencephalography (EEG) which have demonstrated that both chronic and acute cannabinoid exposure disrupts neural oscillations in humans. We also offer a hypothetical framework through which endocannabinoids modulate neural synchrony at the network level. This also includes speculation on how both chronic and acute cannabinoids disrupt functionally relevant neural oscillations by altering the fine tuning of oscillations and the inhibitory/excitatory balance of neural circuits. Finally, we highlight important clinical implications of such oscillatory disruptions, such as the potential relationship between cannabis use, altered neural synchrony, and disruptions in sensation, perception, and cognition, which are perturbed in disorders such as schizophrenia.

Facilitated extinction of conditioned fear responses by delta 9-tetrahyrdrocannabidol in humans: a pilot study

OBJECTIVE

We sought to determine whether acute delta 9-tetrahyrdrocannabidol (THC) administration would facilitate fear extinction in young occasional cannabis users, given that animal models indicate THC facilitates extinction learning, and recent studies indicate THC administration may also enhance threat memory extinction in humans.

METHODS

On each of the 2 days, 24+ hour THC-deprived participants were conditioned to fear visual stimuli in a delay conditioning and extinction paradigm. Both CS+ and CS- were faces of negative emotional valence, with the CS+ paired with mild electric shock. Throughout both conditioning and extinction paradigms, EEG was measured to quantify event-related potentials for these learning processes. Following conditioning, individuals, in a randomized and counter-balanced order, smoked either an active THC cigarette (26.25 mg/2.7% THC) or a placebo marijuana cigarette (0.002% THC) on 1 day and the opposite cigarette on the second day. After smoking, CS+ and CS- were presented without shock, resulting in extinction of conditioned fear.

RESULTS

Relative to placebo, THC facilitated extinction of the conditioned response to the CS+, as reflected by reductions in late positive potential amplitude during extinction learning.

CONCLUSIONS

The results indicate that acute THC administration may facilitate extinction of the conditioned fear response in humans.