Abstract
(1) Background: Transcranial magnetic stimulation (TMS) approaches are widely used to study cortical and corticospinal function. However, responses to TMS are subject to significant intra-and inter-individual variability. Acute and chronic exposure to recreational substances alters the excitability of the sensorimotor system and may contribute to the variability in TMS outcome measures. The increasing prevalence of recreational substance use poses a significant challenge for executing TMS studies, but there is a lack of clarity regarding the influence of these substances on sensorimotor function. (2) Methods: The literature investigating the influence of alcohol, nicotine, caffeine and cannabis on TMS outcome measures of corticospinal, intracortical and interhemispheric excitability was reviewed. (3) Results: Both acute and chronic use of recreational substances modulates TMS measures of excitability. Despite the abundance of research in this field, we identify knowledge gaps that should be addressed in future studies to better understand the influence of these substances on TMS outcomes. (4) Conclusions: This review highlights the need for TMS studies to take into consideration the history of participant substance use and to control for acute substance use prior to testing.
Highlights
Transcranial magnetic stimulation (TMS) has been extensively used to non-invasively probe the motor system in healthy and clinical populations to study the neural mechanisms of human movement and evaluate neuroplasticity
Acute nicotine intake increased Intracortical facilitation (ICF) in smokers and did not modulate Short-latency afferent inhibition (SAI) or short-interval intracortical inhibition (SICI) [129]. These findings may be explained by the evidence mentioned above, where chronic exposure to nicotine may lead to the desensitization of non-α7 nicotinic acetylcholine receptors (nAChRs) that modulated GABAergic neurotransmission, while glutamatergic neurotransmission remains elevated [120]
According to the studies reviewed both acute and chronic use of recreational substances appear to modulate the excitability of the motor system, reflected by a change in TMS outcome measures
Summary
Transcranial magnetic stimulation (TMS) has been extensively used to non-invasively probe the motor system in healthy and clinical populations to study the neural mechanisms of human movement and evaluate neuroplasticity. Short-latency afferent inhibition (SAI) and contraction during isometric contraction the right-hand muscle leads to an interruption of voluntary long-latency afferent inhibition (LAI) occurs when electrical peripheral NS is delivered prior to the known as the cortical silent period (CSP). Long-interval intracortical inhibition (LICI) is measured when a suprathreshold CS is delivered 50–300 ms prior to a suprathreshold TS, leading to inhibition of the MEP. There are no official guidelines regarding the screening of other common, recreational substances including cannabis, nicotine and caffeine At present, it is unclear whether or how short-and long-term use of these substances are capable of inducing changes in neuronal excitability that is reflected in TMS measures or their variability. The review focuses on recreational substance use of alcohol, cannabis, caffeine and nicotine, and their impact on measures of corticospinal and cortical excitability
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