Background: Cognitive fatigue impairs performance across multiple domains, yet how regular cannabis use affects fatigue responses remains unclear. This pilot study investigated neural and behavioural correlates of cognitive fatigue in abstinent cannabis users versus non-users. Methods: Twenty-six participants (18 non-users, 8 regular cannabis users after 24-hour abstinence) completed cognitive tasks before and after a 60-minute Sustained Attention to Response Task (SART) designed to induce fatigue. Tasks assessed working memory (N-Back), cognitive flexibility (Wisconsin Card Sorting), psychomotor speed (Digit Symbol Substitution), sustained attention (Continuous Performance Task), inhibition (Stroop, Stop Signal), and motion perception. Functional near-infrared spectroscopy (fNIRS) continuously monitored prefrontal cortex activation across 20 channels organized into 7 regions of interest. Results: Both groups reported increased subjective fatigue (VAS-F) post-SART. Behaviourally, most cognitive tasks showed practice effects rather than fatigue-related decrements. FNIRS revealed divergent patterns: non-users showed increased prefrontal HbO values post-SART (110% increase), while cannabis users showed decreased HbO values (shifting from positive to negative). Effect sizes for group differences were medium to large for several tasks (Stroop, d = -0.58; Digit Symbol, d = -0.55; CPT, d = -0.50) despite not reaching statistical significance due to limited power. Conclusions: This exploratory study suggests abstinent cannabis users and non-users show opposing neural adaptation patterns to cognitive fatigue. While underpowered for definitive conclusions, the divergent hemodynamic responses warrant investigation with larger samples to understand how cannabis use history affects fatigue vulnerability. Keywords: Cognitive fatigue, mental fatigue, sustained attention, cannabis, fNIRS, neuroimaging, prefrontal cortex, motion coherence, pilot study
Mariia Vistyzenko (Thu,) studied this question.