VRT as a Biomarker of Cerebellar Dysfunction in Chronic Cannabis Use

Study Overview
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Brief Summary
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Chronic cannabis consumption has been associated with poor psychosocial functioning that could be associated to cerebellar dysfunction. The cerebellum has a relevant role in adaptation processes and has a high density of cannabinoid 1 receptor (CB1R). Implicit motor learning is a cerebellum dependent function that can be measured with a visuomotor rotation task (VRT). The project aims to identify a sensitive and specific biomarker of cerebellum dysfunction in chronic cannabis users. The investigators would like to demonstrate that the visuomotor rotation paradigm is valid to measure and quantify such a dysfunction. A longitudinal prospective study with a 3 month follow-up is proposed. 3 groups will be included: 1) chronic cannabis users; 2) individuals with an alcohol use disorder; and 3) healthy controls. All groups will be matched by sex and age. Forty individuals will be included in each group. Individuals will be assessed at baseline, at first month and at 3-months of follow-up. Sociodemographic and clinical data will be recorded. Information on cannabis consumption will be registered using an App. Participants will do the visuomotor rotation task and answer three questionnaires: the Intrinsic Motivation Inventory, the Scale for the assessment and rating of ataxia (SARA) and the Harris tests for lateral dominance. The biomarker developed by this project will facilitate the detection of cerebellar alterations in chronic cannabis users, and will permit to quantify and monitor such alteration over time. The team's intention is to patent the proposed model and disseminate it in order to use it in clinical practice at both primary and specialized health centres.

Detailed Description
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The subjects have to realize movements towards a target, at a digitizing tablet, holding a digitizing pencil. Visual feedback is projected on a screen surface in front of the subject, which hides the sight of actual movements from the latter. In the experimental condition of rotation, the experimenter introduces a rotation of 45 grades between the movement realized by the subject and the visual feedback that is provided on the screen. Then, the subject is provided with a strategy in order to overcome this perturbation: that is, to make the movement aiming 45 grades to the opposite direction from the introduced rotation. This explicit strategy leads to immediate correction of the error, but as the time passes subjects tend to commit more and more errors due to implicit motor adaptation. This happens because the motor control system tends to correct the perceived perturbation between the anticipated and the actual location of the hand in an automatic and unconscious way. The conflict between the implicit and explicit strategies has the surprising consequence of a persistent and accumulative deterioration of performance that can only be resolved when the participants abandon the explicit strategy. Subjects with cerebellar damage show deficits in implicit motor learning and for this reason they do not show this progressive deterioration of performance. Given that chronic cannabis abuse can lead to cerebellar damage, the investigators hypothesize that subjects from the experimental group 1 (cannabis use) will have a significant smaller directional error on the rotation condition than controls. A second hypothesis is that this effect will be cannabis-specific, due to the high CB1R concentration on the cerebellum, so the alcohol dependence group is expected to perform similarly to control group

Official Title
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A Visuomotor Rotation Task as a Biomarker of Cerebellar Dysfunction in Chronic Cannabis Use

Conditions
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Healthy, Cannabis Use, Alcohol Use Disorder

Intervention / Treatment
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* Diagnostic Test: Visuomotor adaptation task


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: 18-50 years old Right-handed Daily consumption of cannabis for at least 2 years (cannabis group) or diagnosed Alcohol Use Disorder (alcohol group) Exclusion Criteria: Non-corrected visual deficits Regular consumption of other drugs except nicotine Other Axis I or neurological diagnosis

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 50 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Group 1 -Chronic cannabis use<br>Individuals between 18 and 50 years old who have been using at least 2 joints per day for at least 3 years. They should have used cannabis during the last 24h but not during the 3h prior to participation to the study and they should test positive for cannabis in their urine. Individuals with another substance use or severe mental disorder will be excluded (except tobacco use) | Diagnostic Test: Visuomotor adaptation task<br>* We will measure performance of the subjects of each group on the visuomotor adaptation task, especially in the rotation condition, in which a perturbation will be induced between the anticipated location of the hand and the provided visual feedback, and in the washout condition, in which the rotation will be removed. We expect that subjects with cannabis use disorder will not show the expected implicit motor adaptation to the perturbation and consequently no deterioration of performance on the task, due to cannabis-induced cerebellar damage. In other words, we want to show that this visuomotor task is a cheap and quick biomarker of cerebellar dysfunction in chronic cannabis users.<br>|
| Group 2 - Alcohol dependence<br>Individuals between 18 and 50 years old diagnosed with alcohol use disorder according to DSM-V criteria and have been consuming alcohol for at least 3 years. Individuals who are diagnosed with another substance use or severe mental disorder will be excluded (except tobacco use). | Diagnostic Test: Visuomotor adaptation task<br>* We will measure performance of the subjects of each group on the visuomotor adaptation task, especially in the rotation condition, in which a perturbation will be induced between the anticipated location of the hand and the provided visual feedback, and in the washout condition, in which the rotation will be removed. We expect that subjects with cannabis use disorder will not show the expected implicit motor adaptation to the perturbation and consequently no deterioration of performance on the task, due to cannabis-induced cerebellar damage. In other words, we want to show that this visuomotor task is a cheap and quick biomarker of cerebellar dysfunction in chronic cannabis users.<br>|
| Control Group<br>Individuals matched in gender and age with the experimental groups and with no diagnosis of substance use or severe mental disorder (except tobacco use) | Diagnostic Test: Visuomotor adaptation task<br>* We will measure performance of the subjects of each group on the visuomotor adaptation task, especially in the rotation condition, in which a perturbation will be induced between the anticipated location of the hand and the provided visual feedback, and in the washout condition, in which the rotation will be removed. We expect that subjects with cannabis use disorder will not show the expected implicit motor adaptation to the perturbation and consequently no deterioration of performance on the task, due to cannabis-induced cerebellar damage. In other words, we want to show that this visuomotor task is a cheap and quick biomarker of cerebellar dysfunction in chronic cannabis users.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in directional error between baseline and after cessation of cannabis use | Directional error of hand movement trajectories towards the target object on the rotation condition of the visuomotor rotation task. | The visuomotor adaptation task duration will not exceed 20 minutes and subjects are expected to realize it at three different time points: baseline, 1 month, 3 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Visuomotor task