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Long-term effects of cannabis on oculomotor function in humans

Institute of Psychology, RWTH Aachen University, Aachen, Germany Lynn.Huestegge{at}psych.rwth-aachen.de

R Radach

Florida Center for Reading Research, Florida State University, Tallahassee, Florida, USA

HJ Kunert

Division of Clinical Neuroscience, Max Planck Institute for Experimental Medicine, Gottingen, Germany

Abstract

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.

Key Words: adverse effects • cannabis • eye movements • long-term effects • oculomotor control • saccades • THC

This version was published on August 1, 2009

Journal of Psychopharmacology, Vol. 23, No. 6, 714-722 (2009)
DOI: 10.1177/0269881108091601


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