Physiology of Human Brain Connectivity

Summary

The purpose of this study is to investigate the effective connectivity between different regions of the human brain in healthy participants, and the mechanisms which influence and modulate its development. Specifically, the investigators will examine the effects of cortico-cortical paired associative stimulation (ccPAS) which is induced by the application of brief (\< 1 ms) transcranial magnetic stimulation (TMS) pulses separated by a short millisecond-level time intervals ("asynchrony") to two different areas of the brain. All techniques are non-invasive and considered safe in humans: TMS, electroencephalography (EEG), and magnetic resonance imaging (MRI). Based on previous animal and human studies, it is hypothesized that ccPAS will increase or decrease effective connectivity between the stimulated areas depending on the asynchrony value. The main outcome measure is source-resolved EEG cortico-cortical evoked potentials (ccEPs) elicited by single-pulse TMS.

Conditions

• Healthy

Interventions

DEVICE

Single-pulse transcranial magnetic stimulation (spTMS)

Single-pulse TMS (spTMS) will be delivered with a TMS stimulator (MagPro X100 w/ MagOption, MagVenture, Farum, Denmark) and a figure-of-eight TMS coil. 80 spTMS will be repeated at 0.2 Hz. An MRI-based TMS navigation system will be used to navigate the TMS coil (Localite, Bonn, Germany).

DEVICE

Paired associative stimulation (PAS)

Paired associative stimulation (PAS) will be applied with two TMS stimulators (MagPro X100 w/ MagOption, MagVenture, Farum, Denmark) and two TMS coils. The pulses from each stimulator/coil will be repeated at 0.2 Hz, duration of run 15 minutes (180 pulses for each stimulator/coil). In different sessions, we will deliver PAS with different asynchrony values to examine their effects on effective connectivity. Coils will be navigated using an MRI-based TMS navigation system (Localite, Bonn, Germany).

DIAGNOSTIC_TEST

Magnetic resonance imaging (MRI)

Structural, diffusion, and functional MRI with a 3-Tesla Siemens scanner

Sponsors & Collaborators

• National Institute of Neurological Disorders and Stroke (NINDS)

  collaborator NIH

• Massachusetts General Hospital

  lead OTHER

Principal Investigators

• Tommi Raij, MD, PhD · Massachusetts General Hospital

Study Design

Allocation

NA

Purpose

BASIC_SCIENCE

Masking

NONE

Model

SINGLE_GROUP

Eligibility

Min Age

18 Years

Max Age

64 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2024-12-13

Primary Completion

2027-04-15

Completion

2027-04-15

Countries

• United States

Study Locations