Motion Discrimination is Impaired in Cannabis Users.
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1
University of Newcastle, School of Psychology, Australia
Chronic cannabis use is associated with deficits in visual attention and perception, and reduced dopamine levels, especially with early-onset use. Motion perception is impaired with altered dopaminergic functioning in people with Schizophrenia and Parkinson's disease and in abstaining drug users. Such deficits in motion perception have been shown to be exacerbated at low contrast and in low luminance conditions. This study tested the hypothesis that early-onset cannabis users will show impaired motion perception under low light conditions compared to controls. Motion coherence thresholds were collected from 19 controls (11 male, mean age 22.4 years) and 14 cannabis users (8 male, mean age 23.6 years). Participants completed two discrimination of direction of motion (radial and translational) tasks at three luminance levels (69, 3 and 0.5cd/m2). In each task 50 dots were presented on the screen for 500msec, moving at 5.6 d/sec speed upward or downward in the translational task, and inward or outward in the radial task. The contrast of the dots was at 12 and 24% and varied pseudo-randomly across trials in each task. A two-alternative forced choice paradigm (direction discrimination: upward vs downward; inward vs outward) and a two-down, one-up staircase procedure were employed. The interaction between contrast and group (F1,31=5.6741, p=0.02) was significant. The groups did not differ at 12% contrast however at 24% contrast the coherence threshold was higher for the cannabis group than the controls. This effect was modified by a trend towards a significant interaction between motion type, contrast and group (F1,31=3.8643, p=0.058), which suggested that this effect was confined to the radial direction of motion. This is the first study showing that abstaining cannabis users present a specific deficit in processing of complex motion such as radial motion. These results suggest that cannabis users can be impaired in everyday tasks such as driving.
Keywords:
Visual Perception,
Cannabis use,
radial motion,
Low contrast,
motion coherence threshold
Conference:
XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014.
Presentation Type:
Poster
Topic:
Sensation and Perception
Citation:
Mikulskaya
E and
Martin
F
(2015). Motion Discrimination is Impaired in Cannabis Users..
Conference Abstract:
XII International Conference on Cognitive Neuroscience (ICON-XII).
doi: 10.3389/conf.fnhum.2015.217.00254
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Received:
19 Feb 2015;
Published Online:
24 Apr 2015.
*
Correspondence:
Ms. Elena Mikulskaya, University of Newcastle, School of Psychology, Ourimbah, Australia, c3176499@uon.edu.au