The neural oscillations serving task switching are altered in cannabis users

Area of Science:

• Neuroscience
• Cognitive Science
• Psychiatry

Background:

• Cannabis use is known to affect attention, but its impact on cognitive flexibility, a key executive function, is less understood.
• The neural mechanisms, specifically brain's oscillatory dynamics, underlying these potential cognitive changes in cannabis users remain poorly investigated.

Purpose of the Study:

• To investigate the neural oscillatory dynamics associated with cognitive flexibility in chronic cannabis users compared to nonusers.
• To identify alterations in brain activity during a task-switching paradigm using magnetoencephalography (MEG).
• To correlate observed neural changes with the degree of cannabis use involvement.

Main Methods:

• 25 chronic cannabis users and 30 nonuser controls underwent neuropsychological testing and a task-switching paradigm during MEG.
• A data-driven statistical approach identified time-frequency windows of interest for analysis.
• Whole-brain neural switch cost maps were computed by comparing oscillatory activity during switch versus no-switch conditions.

Main Results:

• Cannabis users exhibited reduced theta switch cost responses in the dorsolateral and dorsomedial prefrontal cortices compared to nonusers.
• Nonusers displayed typical increased neural recruitment during task switching.
• Theta activity in the dorsomedial prefrontal cortex significantly correlated with the level of cannabis use.

Conclusions:

• Chronic cannabis use is associated with altered theta switch cost activity in prefrontal cortical regions vital for cognitive flexibility.
• These findings suggest a link between cannabis use and aberrant neural oscillatory activity underlying cognitive flexibility, which is dependent on the extent of use.