Long-term effects of cannabis on oculomotor function in humans.
Cannabis is known to affect human cognitive and visuomotor skills directly after consumption. Some studies even point to rather long-lasting effects, especially after chronic tetrahydrocannabinol (THC) abuse. However, it is still unknown whether long-term effects on basic visual and oculomotor processing may exist. In the present study, the performance of 20 healthy long-term cannabis users without acute THC intoxication and 20 control subjects were examined in four basic visuomotor paradigms to search for specific long-term impairments. Subjects were asked to perform: 1) reflexive saccades to visual targets (prosaccades), including gap and overlap conditions, 2) voluntary antisaccades, 3) memory-guided saccades and 4) double-step saccades. Spatial and temporal parameters of the saccades were subsequently analysed. THC subjects exhibited a significant increase of latency in the prosaccade and antisaccade tasks, as well as prolonged saccade amplitudes in the antisaccade and memory-guided task, compared with the control subjects. The results point to substantial and specific long-term deficits in basic temporal processing of saccades and impaired visuo-spatial working memory. We suggest that these impairments are a major contributor to degraded performance of chronic users in a vital everyday task like visual search, and they might potentially also affect spatial navigation and reading.
Institute of Psychology, RWTH Aachen University, Aachen, Germany. Lynn.Huestegge@psych.rwth-aachen.de
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D000328:Adult; D003627:Data Interpretation, Statistical; D013759:Dronabinol / Q000494:pharmacology*; D005133:Eye Movements / Q000187:drug effects*; D005260:Female; D005403:Fixation, Ocular / Q000502:physiology; D006213:Hallucinogens / Q000494:pharmacology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000502:physiology; D009801:Oculomotor Muscles / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D012438:Saccades / Q000187:drug effects; D055815:Young Adult
D006213:Hallucinogens; D013759:Dronabinol