Transcranial Magnetic Stimulation for Investigating Causal Brain-behavioral Relationships and their Time Course

Abstract

Transcranial magnetic stimulation (TMS) is a safe, non-invasive brain stimulation technique that uses a strong electromagnet in order to temporarily disrupt information processing in a brain region, generating a short-lived "virtual lesion." Stimulation that interferes with task performance indicates that the affected brain region is necessary to perform the task normally. In other words, unlike neuroimaging methods such as functional magnetic resonance imaging (fMRI) that indicate correlations between brain and behavior, TMS can be used to demonstrate causal brain-behavior relations. Furthermore, by varying the duration and onset of the virtual lesion, TMS can also reveal the time course of normal processing. As a result, TMS has become an important tool in cognitive neuroscience. Advantages of the technique over lesion-deficit studies include better spatial-temporal precision of the disruption effect, the ability to use participants as their own control subjects, and the accessibility of participants. Limitations include concurrent auditory and somatosensory stimulation that may influence task performance, limited access to structures more than a few centimeters from the surface of the scalp, and the relatively large space of free parameters that need to be optimized in order for the experiment to work. Experimental designs that give careful consideration to appropriate control conditions help to address these concerns. This article illustrates these issues with TMS results that investigate the spatial and temporal contributions of the left supramarginal gyrus (SMG) to reading.

Time-Frequency Analysis of Motor-Evoked Potential in Patients with Stroke vs Healthy Subjects: a Transcranial Magnetic Stimulation Study

“…RMT was observed to be~33% higher in patients (p = 0.015) as compared to healthy subjects. MEP amplitude was observed to be lower by~50% and latency was higher by~26% (Table 2) in patients, might be indicating loss of upper motor neurons (UMN) or affected cortico-spinal tract or peripheral nerves in stroke [2,8,29]. The trend of SRC (Fig.…”

“…Since the discovery of magnetic stimulation of the brain, transcranial magnetic stimulation (TMS) has been used in numerous clinical applications with its therapeutic potential being an active research area [1]. TMS has been shown to be a valuable tool in studying the regional localization [2], connectivity of brain [3], pathophysiology of neurological disorders [4], and diagnostic utility [5]. TMS technology has its advantage of being non-invasive, painless, good spatiotemporal resolution, and ability to control the amount of stimulation intensity to be delivered [6,7].…”

“…Motorevoked potential (MEP) obtained using transcranial magnetic stimulation (TMS) can be recorded as electromyogram (EMG) activity in a target muscle. MEP encapsulates information relevant to the cortical excitability of the brain [1] providing insights into membrane excitability of neurons, conduction and functional integrity of cortico-spinal tract, and neuromuscular junctions and is of prognostic importance in disease monitoring [2].…”

Occipital tACS bursts during a visual task impact ongoing neural oscillation power, coherence and LZW complexity

“…In this study, we examined first how tACS alters short-term physiology using a burst-EEG protocol that provides a small delay window to study concurrent tCS effects, and then how such effects are causally related to both secondary physiological effects and behavior, a technique already exploited with other stimulation techniques such as TMS [48]. tACS was used to probe the causal relationship between oscillatory activity within the occipital cortex and change-of-speed visual task, where subjects are instructed to detect a change on the acceleration of the visual stimuli ( Figure 1A).…”

Multifunctional Setup for Studying Human Motor Control Using Transcranial Magnetic Stimulation, Electromyography, Motion Capture, and Virtual Reality

“…Transcranial Magnetic Stimulation Stereotaxic Localization 1. Calibrate hardware and software designed for TMS registration 12 , to allow for accurate coil placement. This generally involves coregistering TMS coils with anatomical landmarks such as the nasion, preauricular points, and nose tip.…”