Study of Neuroplasticity on Depressed Patients : Modulation of MEP Induced by Theta Burst Stimulation

Study of Neuroplasticity on Depressed Patients Versus Healthy Subjects : Modulation of the MEP Size Induced by Theta Burst Stimulation

Neuroplasticity is supposed to be altered in patients suffering from a Major Depressive Disorder (MDD). Transcranial Magnetic Stimulation is a medical device which measures cerebral plasticity. Several parameters of cortical excitability are available for that purpose. These parameters are altered on patients wth MDD and these modifications are corrected after treatment. Therefore results in the studies are very heterogeneous. Theta Burst Stimulation (TBS) is a type a Transcranial Magnetic Stimulation (TMS) protocol and can induce cerebral plasticity. The cerebral plasticity induced by TBS was measured on a group of patients suffering from Asperger's disease (ASD) versus a control group. The plasticity was significantly different in patients with ASD. The aim of our study is to study the neuroplasticity induced by TBS on a patients with MDD.

The study is lead with patients suffering from a MDD. All patients are drug free. Patients are compared to a control group of healthy subjects The protocol has 2 sessions. During the first session, After determining the parameters of stimulation (stimulated target : part of the left motor cortex responsible for the contraction of the right first dorsal interosseous muscle ; Activity Motor Threshold (AMT) ; Intensity of Stimulation providing a Motor Evoked Potential (MEP) with an Amplitude of 1mV (MEP 1mV)), a Baseline consisting of 15 MEP (intensity MEP 1mV) is measured. Then each subjet receive a TBS protocol (cTBS or iTBS) (intensity of stimulation 80% of AMT). After receiving the stimulation, sets containing 10 MEP are regularly measured by each subject.

During a second session, the same protocol is done again with the other TBS stimulation (cTBS or iTBS) the subject didn't get during the first session.

A neuronavigation device is used to determine precisely the area of stimulation.

Inclusion Criteria:

Subjects with MDD

• MDD according to definition provided by the DSM V
• No antidepressant Healthy Controls
• No present psychiatric disease

Exclusion Criteria:

• depression with Melancholic features
• pregnancy
• contra indication in the use of TMS (personal history of epilepsy, deep brain stimulation, vague nerve stimulation, pace maker, intracerebral lesion, pieces of metal Inside of the brain)
• diseases with neurological effects (multiple sclerosis, Parkinson disease, HIV...)