This study will evaluate the impact of regular use of cannabis on the spatial sensitivity of magnocellular system (visual event-related potential, visual ERP). Secondary purposes of this study are to evaluate the impact of regular use of cannabis on the temporal sensitivity of magnocellular system (visual event-related potential), on the dynamics of cortical visual processing during face perception test (visual event-related potential) and on functioning of retinal photopic and scotopic systems (electroretinogram). The ancillary study is a genetic analysis of a group of candidate genes that aims to identify biomarkers for changes in visual processing. This will allow to distinguish among more homogeneous and specific groups in future studies on larger cannabis user population. This ancillary study concerns all participants subject to their informed consent (facultative study).
Study Type
INTERVENTIONAL
Allocation
NON_RANDOMIZED
Purpose
OTHER
Masking
NONE
Enrollment
163
Stimuli are black and white grids, having different range of spatial frequencies, presented with different contrasts on a grey background thanks to a computer monitor, in a dark room. Participants are requested to maintain central fixation. During the test patients stay sit, head hold by chin strap. A pause can be asked by participant and done at every moment. This test lasts approximately 30 minutes.
Two vertical bars are showed on a monitor, on the link and right of point of central fixation. Bars appear simultaneously or with a 10 to 200 ms asynchrony. Participants must determine whether stimuli are simultaneous or asynchronous and answer pressing the link button for simultaneity or right button for asynchrony. During the test patients stay sit, head hold by chin strap. A pause can be asked by participant and done at every moment. This test lasts approximately 30 minutes.
Faces filtered in different spatial frequence ranges are showed randomly on a monitor, in a dark room. Participants must maintain a central fixation thank to a fixation cross. During the test patients stay sit, head hold by chin strap. A pause can be asked by participant and done at every moment. This test lasts approximately 30 minutes.
In case of specific consent of participant to ancillary study, for ancillary study
Maison des Addictions - CHU de Nancy, Hôpital St Julien
Nancy, France
Amplitude of P100 wave in contrast sensibility test
Time frame: up to 1 month
Culmination time of the P100 wave in contrast sensibility test
Time frame: up to 1 month
Amplitude of P100 wave in visual simultaneity test
Time frame: up to 1 month
Culmination time of P100 wave in visual simultaneity test
Time frame: up to 1 month
Amplitude of P100 wave in face perception test
Time frame: up to 1 month
Amplitude of N170 wave in face perception test
Time frame: up to 1 month
Culmination time of P100 wave in face perception test
Time frame: up to 1 month
Culmination time of N170 wave in face perception test
Time frame: up to 1 month
Amplitude of "a" wave in different ERG sequences
Time frame: day 0
Amplitude of "b" wave in different ERG sequences
Time frame: day 0
Culmination time of "a" wave in different ERG sequences
Time frame: day 0
Culmination time of "b" wave in different ERG sequences
Time frame: day 0
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