Influence of Repetitive Transcranial Magnetic Stimulation (rTMS) Challenge on Cognitive and Functional Magnetic Resonance Imaging Markers in Healthy Subjects

Overview

Episodic and working memory processes are the most affected cognitive domains in Alzheimer's Disease (AD) and its early stage, Mild Cognitive Impairment (MCI). Transcranial Magnetic Stimulation (TMS) is a unique tool to interfere with cognitive processes by inducing "virtual and transient lesions", mimicking those observed in MCI. It has proven repeatedly its capacity to interfere with encoding-retrieval memory task. However, to date, only few imaging data exist on the cerebral pathways involved in encoding memory task. Moreover, the stability of TMS effects over time remains to be investigated. If proven to be a stable interfering challenge, TMS could be used to investigate the potential restoring effect of new medication in AD. The study is the pilot study of a larger clinical trial which aims to prove the utility of rTMS as a potential model for prediction of clinical efficacy using a combination of cognitive and neuroimaging endpoints.

Episodic and working memory processes are the most affected cognitive domains in Alzheimer's Disease (AD) and its early stage, Mild Cognitive Impairment (MCI). Transcranial Magnetic Stimulation (TMS) is a unique tool to interfere with cognitive processes by inducing "virtual and transient lesions", mimicking those observed in MCI. It has proven repeatedly its capacity to interfere with encoding-retrieval memory task. However, to date, only few imaging data exist on the cerebral pathways involved in encoding memory task. Moreover, the stability of TMS effects over time remains to be investigated. If proven to be a stable interfering challenge, TMS could be used to investigate the potential restoring effect of new medication in AD. The study is the pilot study of a larger clinical trial which aims to prove the utility of rTMS as a potential model for prediction of clinical efficacy using a combination of cognitive and neuroimaging endpoints. This pilot study specifically aims: * to determine the cerebral region to stimulate using functional neuronavigation, * to evaluate the effects of rTMS on behavioral and functional imaging data (functional Magnetic Resonance Imaging, fMRI) * to investigate the stability of the TMS interfering effects by replicating the experimental day up to 4 times. The study is composed of two parts: * Part A: on Day 1, the subjects will perform the episodic memory task in the MRI scanner to determine individual main activations. The mean activation peak obtained by a group analysis will be used as the target coordinates during the part B. Two weeks later, on Day 2, the subjects will repeat the episodic memory task in the MRI scanner. The BOLD signal changes will be compared between Day 1 and Day 2 to investigate the stability of the activations elicited by the memory task. * Part B: subjects will randomly be assigned to Group 1 or 2. * GROUP 1: The subjects will come on 4 different days. On each day, the subjects will perform the episodic memory task while being actively stimulated using rTMS over L-DLPFC and Vertex (control region) in random order and will undergo an fMRI session on Day 1 and Day 2. Later, they will undergo another set of behavioral tasks from the CANTAB battery and will be stimulated by rTMS using a placebo coil. * GROUP 2: The subjects will come on 4 different days. On each day, the subjects will perform the episodic memory task while being actively stimulated using rTMS over L-DLPFC and Vertex (control region) in random order and will undergo an fMRI session on Day 1 and Day 2. Later, they will undergo another set of behavioral tasks from the CANTAB battery and will be stimulated by rTMS using an active coil. Total expected number of subjects: 34 subjects for the Parts A and B PART A: 10 subjects PART B: 24 subjects (12 per group)