A recent brain imaging study published in the Journal of Psychopharmacology reveals that regular cannabis users exhibit reduced spontaneous activity in a critical area of the brain responsible for motor control. The study, which involved 67 adults from Omaha, Nebraska, aimed to understand how cannabis affects brain regions related to movement, an area less explored compared to cognitive functions like memory and attention.
Of the participants, 34 reported using cannabis at least twice a week for six months, while the remaining 33 had no recent cannabis exposure. Both groups were matched for age, gender, and other demographic factors. Participants underwent structured interviews regarding their cannabis use history and completed standardized questionnaires to assess cannabis use disorder symptoms.
Utilizing magnetoencephalography (MEG), a non-invasive technique that measures magnetic fields produced by neural activity with high precision, researchers monitored brain activity during a modified Eriksen flanker task. This task required participants to identify the direction of a central arrow while ignoring conflicting surrounding arrows, which tested both cognitive control and motor response.
Findings indicated that all participants demonstrated normal patterns of brain activity related to motor responses, with typical decreases in beta activity (beta desynchronization) and increases in gamma activity (gamma synchronization) during hand movements. However, when comparing spontaneous activity during rest periods before task trials, cannabis users showed significantly lower gamma activity in the left primary motor cortex, a region that regulates movement on the right side of the body.
The study linked the severity of cannabis use disorder symptoms to lower spontaneous gamma activity. Participants with more intense symptoms displayed reduced gamma power, which also correlated with faster reaction times on the cognitive task. This suggests that diminished spontaneous gamma activity may explain the relationship between cannabis use disorder symptoms and reaction time, indicating a potential connection between altered brain function and behavioral differences.
Despite these differences in brain activity, both cannabis users and non-users performed similarly on the flanker task, showing no significant discrepancies in accuracy or overall speed. This implies that cannabis users may adjust their responses to compensate for the changes in brain activity, maintaining normal task performance.
The observed reduction in spontaneous gamma activity aligns with earlier studies that reported similar decreases in other brain regions among cannabis users, including those involved in sensory processing. Gamma oscillations are thought to facilitate coordinated communication across brain circuits, and their suppression may indicate broader neural communication changes.
The researchers noted that the study had limitations, such as not measuring the exact timing of participants’ last cannabis use and not fully controlling for variations in cannabis potency and consumption methods. The cognitive task used was relatively simple, which may not have been challenging enough to reveal subtle performance differences. Future research could benefit from more complex tasks and larger sample sizes, as well as direct measures of brain chemistry, to better understand the observed effects.
Overall, this study contributes to the growing body of evidence linking regular cannabis use to brain function changes. While these alterations did not hinder performance on the task, the reduction in spontaneous gamma activity raises questions about the long-term effects of heavy cannabis use on brain health and functioning.
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