People with longer histories of regular cannabis use showed weaker implicit motor learning — the kind of automatic sequence learning essential for daily activities — along with elevated resting brain activity.
Neuroscientists studying cannabis cognitive effects, anyone curious about how regular cannabis use affects learning, rehabilitation researchers.
What the researchers found
Comparing 30 regular cannabis users to 32 non-users, researchers found that longer duration of cannabis use was associated with a smaller implicit motor learning index — meaning these individuals were less able to unconsciously learn movement sequences.
Implicit motor learning was measured using the serial reaction time task, where participants respond to visual cues that follow a hidden repeating pattern. People typically speed up on the patterned sequences without consciously realizing there is a pattern. Cannabis users with longer use histories showed less of this automatic speed improvement.
Resting-state EEG revealed a potential neural mechanism: longer cannabis use was associated with increased activity in beta and gamma frequency bands during rest. This elevated baseline cortical activity — described as "supranormal" — may interfere with the neural processes required for implicit learning.
The cannabis group also showed significantly shorter Corsi block spans in both forward and backward conditions, indicating impaired visuospatial short-term and working memory.
Why it matters
Implicit motor learning is fundamental to daily life — it underlies the ability to learn movement sequences for everything from typing to driving to social interaction. This is the first study to link chronic cannabis use to impairment in this specific type of learning, and the EEG data offer a potential brain-level explanation for why it happens.
The numbers in context
30 cannabis users, 32 non-users. Longer cannabis use → smaller implicit motor learning index. Cannabis users: shorter Corsi span (forward and backward). EEG: increased beta and gamma resting activity associated with longer use duration.
How the study worked
Observational study comparing 30 regular cannabis users and 32 non-users. Measures: serial reaction time task (implicit motor learning), Corsi block-tapping test (visuospatial memory), and resting-state EEG (cortical activity in beta and gamma bands). Duration of cannabis use correlated with learning and EEG outcomes.
Who was studied
N=62 adults (30 cannabis users and 32 non-users), mixed sex, aged 18-35.
What this study cannot tell us
Cross-sectional design cannot establish that cannabis caused the learning impairment — it may reflect pre-existing differences. Small sample size limits statistical power. Cannot control for all confounders (other substance use, sleep quality, education). Cannabis use was self-reported and varied in frequency and potency.
How to read the evidence
Small observational study with neurophysiological measures — provides interesting correlational evidence but the cross-sectional design and small sample limit conclusions.
When this study was published
Published in 2026, adding implicit motor learning to the documented cognitive effects of chronic cannabis use.
The bigger picture
Most cannabis cognition research focuses on explicit memory, attention, and executive function. This study adds implicit motor learning to the list of affected domains — a type of learning that operates below conscious awareness and may therefore be harder for users to notice or compensate for. The elevated resting brain activity finding connects to the neuroscience of tolerance (RTHC-00249) and the broader cognitive impact literature, suggesting that chronic cannabis use may alter baseline neural dynamics in ways that cascade across multiple cognitive functions.
Replication
Not stated in abstract.
Funding
Not reported in abstract.
Conflicts of interest
Not reported in abstract.
Questions still open
- Does the implicit motor learning impairment recover with sustained abstinence? Is the elevated resting-state activity a compensatory mechanism or a sign of neural disruption? Do cannabis users notice any real-world consequences of impaired implicit learning (e.g., difficulty learning new physical skills)?
Read the original research
Longer chronic cannabis use in humans is associated with impaired implicit motor learning and supranormal resting state cortical activity.
PloS one, 21(1), e0338082
PloS One is a peer-reviewed open-access journal known for publishing a wide range of scientific research.
Citation
Prashad, Shikha; Paek, Andrew Y; Fournier, Lisa R. (2026). Longer chronic cannabis use in humans is associated with impaired implicit motor learning and supranormal resting state cortical activity.. PloS one, 21(1), e0338082. https://doi.org/10.1371/journal.pone.0338082
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