Cannabis use impacts pre‐stimulus neural activity in the visual cortices of people with HIV

Abstract

People with HIV (PWH) use cannabis at a higher rate than the general population, but the influence on neural activity is not well characterized. Cannabis use among PWH may have a beneficial effect, as neuroinflammation is known to be a critical problem in PWH and cannabis use has been associated with a reduction in proinflammatory markers. Thus, it is important to understand the net impact of cannabis use on brain and cognitive function in PWH. In this study, we collected magnetoencephalographic (MEG) brain imaging data on 81 participants split across four demographically matched groups (i.e., PWH using cannabis, controls using cannabis, non‐using PWH, and non‐using controls). Participants completed a visuospatial processing task during MEG. Time–frequency resolved voxel time series were extracted to identify the dynamics of oscillatory and pre‐stimulus baseline neural activity. Our results indicated strong theta (4–8 Hz), alpha (10–16 Hz), and gamma (62–72 Hz) visual oscillations in parietal–occipital brain regions across all participants. PWH exhibited significant behavioral deficits in visuospatial processing, as well as reduced theta oscillations and elevated pre‐stimulus gamma activity in visual cortices, all of which replicate prior work. Strikingly, chronic cannabis use was associated with a significant reduction in pre‐stimulus gamma activity in the visual cortices, such that PWH no longer statistically differed from controls. These results provide initial evidence that cannabis use may normalize some neural aberrations in PWH. This study fills an important gap in understanding the impact of cannabis use on brain and cognitive function in PWH.

Regular cannabis use modulates the impact of HIV on the neural dynamics serving cognitive control

“…compensate through increased oscillatory strength. These findings are consistent with previous literature that suggests both spontaneous and oscillatory power are altered in regular cannabis users (Edwards et al, 2009;Springer et al, 2021), and that cannabis use in PWH may have a neuroprotective effect, at least in some brain regions (Christopher-Hayes et al, 2021;Hall et al, 2021;Meade et al, 2016).…”

“…Finally, we also found that the association between the strength of spontaneous baseline activity and neural oscillations in the same spectral band was stronger in the dlPFC of cannabis users relative to nonusers, which may indicate that cannabis users are better able to compensate through increased oscillatory strength. These findings are consistent with previous literature that suggests both spontaneous and oscillatory power are altered in regular cannabis users (Edwards et al, 2009; Springer et al, 2021), and that cannabis use in PWH may have a neuroprotective effect, at least in some brain regions (Christopher-Hayes et al, 2021; Hall et al, 2021; Meade et al, 2016).…”

“…Cognitive impairments are thought to arise from dysregulated dopaminergic signaling resulting from an excitatory/inhibitory imbalance due to a reduction in GABAergic inhibitory inputs in the PFC, thus leading to diminished pyramidal cell firing synchrony between neurons in the hippocampus and PFC (Paspalas and Goldman-Rakic, 2005; Skosnik et al, 2016). Studies using MEG and EEG have shown that regular cannabis use is associated with local decreases in power, both at rest and during task performance (Christopher-Hayes et al, 2021; Edwards et al, 2009; Herning et al, 2003; Rangel-Pacheco et al, 2021; Springer et al, 2021). In fact, one study found that those with greater cannabis exposure had the lowest spectral power, and these findings were more pronounced in frontal regions of the brain (Edwards et al, 2009).…”

“…Though studies have found network-level deficits in cognitive control using the flanker task in PWH and cannabis users separately, whether cannabis use modulates the impact of HIV on the neural oscillatory dynamics serving cognitive control remains unknown. Some studies of PWH have found that cannabis use has a normalizing effect on spontaneous and oscillatory deficits (Christopher-Hayes et al, 2021), disruptions in network organization (Hall et al, 2021), and diminished resting-state functional connectivity (Kallianpur et al, 2020). In this study, we exploit the high spatial and temporal precision of MEG to quantify the neural oscillatory dynamics serving cognitive control in PWH who use cannabis (HIV+ cannabis users), PWH who do not use cannabis (HIV+ nonusers), uninfected users (control cannabis users), and nonusers (control nonusers).…”

Retrospective comparison of motor and somatosensory MEG mapping—Considerations for better clinical applications

“…For somatosensory paradigms, epochs were of 0.3 s duration, with 0.0 s defined as stimulation onset and the baseline being the −0.05 to 0.0 s window. Epochs containing artifacts were excluded using a fixed threshold method (i.e., based on artifactual neural amplitude values), supplemented with visual inspection ( Christopher-Hayes et al, 2021 , Spooner et al, 2021a , Wiesman et al, 2021 ). Artifact-free epochs were time-domain averaged with respect to movement or stimulation onset.…”