Electrophysiological Study of the Functioning of Magnocellular Visual Pathway in Regular Cannabis Users
Condition: Cannabis Use
MeSH terms: Marijuana Abuse
Study type: Interventional

Summary: 
      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).
    


Intervention name(s): Electroretinography; Contrast sensitivity test during Electroencephalography; Visual simultaneity test during Electroencephalography; Face perception test during Electroencephalography; CAST (cannabis abuse screening test); PANSS (Positive And Negative Symptoms Scale) test; Delayed Matching to Sample (DMS) test; Spatial Working Memory (SWM) test; Rapid Visual Information Processing (RVP) test; Test for attentional performance (TAP) / Divided Attention; Collection of saliva sample
Intervention type(s): Other; Other; Other; Other; Other; Other; Other; Other; Other; Other; Other
Intervention description(s): 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
Allocation: Non-Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Other
Keywords: cannabis; magnocellular pathway