In Vivo Cortical Excitability Modulation in Major Depressive Disorder

Summary

The pathophysiology of Major Depression Disorder (MDD) is unclear, with several theories for its neurobiological mechanisms. One possible explanation is the presence of altered neuroplasticity, which can be studied by Transcranial Magnetic Stimulation (TMS). Using TMS to study these mechanisms is performed by applying electromagnetic stimuli to the motor cortex, to obtain measures of temporary cortical excitability modulation. It is known that depressed patients with higher cortical modulation are more responsive to a TMS treatment course. However, it is unknown if there are differences in cortical modulation between depressed patients and healthy subjects. Our goal is to answer this question and contribute towards clarification of the neuroplasticity mechanisms underlying MDD. Accordingly, the investigators will access cortical excitability modulation measures in both depressed patients and healthy volunteers and compare their results. The investigators will also re-assess these measures after 6 weeks of antidepressant treatment. Finally, the investigators will study the association between cortical excitability measures and cognitive processes using an innovative cognitive task.

Eligibility

Inclusion criteria (clinical groups):

1\. Diagnosis of major depressive episode or disorder as provided in the Diagnostic and Statistical Manual of Mental Disorders 5 (DSM-5) (American Psychiatric Association. 2013).

Exclusion criteria (clinical groups):

1. Moderate to severe suicide risk;
2. Known personal history of bipolar disorder or psychotic disorder;
3. Alcohol or other substance abuse and/or dependence;
4. Developmental disorder;
5. Dementia;
6. Presence of uncontrolled active medical illness;
7. Known structural lesion of the central nervous system;
8. Electrical or metallic brain implants;
9. Cardiac implants;
10. Epilepsy;
11. Active use of medication known to cause seizures;
12. Pregnancy;
13. Breastfeeding.

For the healthy control group, participants will also be recruited at the Champalimaud Clinical Center, by advertisement in places of public circulation. The recruitment of this population will be done in order to generate a pairing with both clinical groups in terms of age and sex. The same exclusion criteria will be applied, as well as the presence of any history of neuropsychiatric disease. The total number of participants for this study will be approximately 90 volunteers. Exclusion criteria will be assessed through self-report and/or MINI.

Conditions2

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