Changes in Cortical Circuits in Movement Disorders

Chapter

Abstract

Transcranial magnetic stimulation (TMS) can be used to investigate the intracortical circuits within the primary motor cortex (M1) and connections from other cortical areas to the M1. Repetitive TMS (rTMS) is able to modify the cortical excitability and can be used to test the cortical plasticity. In Parkinson’s disease (PD), there are impairments in intracortical circuits, indicating abnormal modulation of M1 excitability by intrahemispheric and interhemispheric inputs. Organic and psychogenic dystonia may have similar impairment in intracortical circuits but may have differences in cortical plasticity. Essential tremor and PD tremor respond differently to a resetting stimulus applied to different sites along the pathway for tremor generation and transmission, suggesting that they have different pathophysiological origins. Intracortical circuits may be impaired in Tourette’s syndrome but tend to normalize during task performance. Repeated applications of rTMS may induce long-term changes in cortical excitability. It is being developed as a potential treatment to normalize cortical excitability and intracortical circuits for movement disorders.

Keywords

Dystonia Motor evoked potential Parkinson’s disease Tourett’s syndrome Transcranial magnetic stimulation Tremor 

Abbreviations

AMT

Active motor threshold

CBI

Cerebellar inhibition

CMCT

Central motor conduction time

CS

Conditioning stimulus

D-wave

Direct wave

DBS

Deep brain stimulation

EMG

Electromyogram

ET

Essential tremor

GABA

Gamma-aminobutyric acid

I-wave

Indirect wave

ICF

Intracortical facilitation

ISI

Interstimulus interval

LAI

Long latency afferent inhibition

LICI

Long interval intracortical inhibition

LIHI

Long latency interhemispheric inhibition

M1

Primary motor cortex

MEP

Motor evoked potential

PAS

Paired associative stimulation

PD

Parkinson’s disease

RMT

Rest motor threshold

rTMS

Repetitive transcranial magnetic stimulation

SAI

Short latency afferent inhibition

SICF

Short interval intracortical facilitation

SICI

Short interval intracortical inhibition

SIHI

Short latency interhemispheric inhibition

SP

Silent period

TMS

Transcranial magnetic stimulation

TS

Test stimulus

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Copyright information

© Springer Berlin Heidelberg 2012

Authors and Affiliations

  1. 1.Division of Neurology, Krembil Neuroscience Centre and Toronto Western Research InstituteUniversity Health Network, University of TorontoTorontoCanada
  2. 2.7MC-411, Toronto Western HospitalTorontoCanada

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