Inter-individual variability in cortical excitability and motor network connectivity following multiple blocks of rTMS

Anatomically plausible networks of functionally inter-connected regions have been reliably demonstrated at rest, although the neurochemical basis of these ‘resting state networks’ is not well understood. In this study, we combined magnetic resonance spectroscopy (MRS) and resting state fMRI and demonstrated an inverse relationship between levels of the inhibitory neurotransmitter GABA within the primary motor cortex (M1) and the strength of functional connectivity across the resting motor network. This relationship was both neurochemically and anatomically specific. We then went on to show that anodal transcranial direct current stimulation (tDCS), an intervention previously shown to decrease GABA levels within M1, increased resting motor network connectivity. We therefore suggest that network-level functional connectivity within the motor system is related to the degree of inhibition in M1, a major node within the motor network, a finding in line with converging evidence from both simulation and empirical studies.

Download Full-text

Dynamics of brain connectivity after stroke

Reviews in the Neurosciences ◽

10.1515/revneuro-2018-0082 ◽

2019 ◽

Vol 30 (6) ◽

pp. 605-623 ◽

Cited By ~ 5

Author(s):

Adela Desowska ◽

Duncan L. Turner

Keyword(s):

Brain Connectivity ◽

Effective Connectivity ◽

Network Connectivity ◽

Connectivity Pattern ◽

Compensatory Mechanisms ◽

Neural Structure ◽

Motor Network ◽

The Central Nervous System ◽

Dynamic Time ◽

The Impact

Abstract Recovery from a stroke is a dynamic time-dependent process, in which the central nervous system reorganises to accommodate for the impact of the injury. The purpose of this paper is to review recent longitudinal studies of changes in brain connectivity after stroke. A systematic review of research papers reporting functional or effective connectivity at two or more time points in stroke patients was conducted. Stroke leads to an early reduction of connectivity in the motor network. With recovery time, the connectivity increases and can reach the same levels as in healthy participants. The increase in connectivity is correlated with functional motor gains. A new, more randomised pattern of connectivity may then emerge in the longer term. In some instances, a pattern of increased connectivity even higher than in healthy controls can be observed, and is related either to a specific time point or to a specific neural structure. Rehabilitation interventions can help improve connectivity between specific regions. Moreover, motor network connectivity undergoes reorganisation during recovery from a stroke and can be related to behavioural recovery. A detailed analysis of changes in connectivity pattern may enable a better understanding of adaptation to a stroke and how compensatory mechanisms in the brain may be supported by rehabilitation.

Download Full-text

P82. Motor network connectivity predicts responsiveness to theta-burst stimulation

Clinical Neurophysiology ◽

10.1016/j.clinph.2015.04.215 ◽

2015 ◽

Vol 126 (8) ◽

pp. e134

Author(s):

C. Nettekoven ◽

L.J. Volz ◽

M. Kutscha ◽

E.-M. Pool ◽

S.B. Eickhoff ◽

...

Keyword(s):

Network Connectivity ◽

Theta Burst Stimulation ◽

Burst Stimulation ◽

Motor Network ◽

Theta Burst

Download Full-text

Response Inhibition Deficits and Altered Motor Network Connectivity in the Chronic Phase of Pediatric Traumatic Brain Injury

Journal of Neurotrauma ◽

10.1089/neu.2017.5081 ◽

2017 ◽

Vol 34 (22) ◽

pp. 3117-3123 ◽

Cited By ~ 6

Author(s):

Jaclyn A. Stephens ◽

Cynthia E. Salorio ◽

Jerald P. Gomes ◽

Mary Beth Nebel ◽

Stewart H. Mostofsky ◽

...

Keyword(s):

Traumatic Brain Injury ◽

Brain Injury ◽

Response Inhibition ◽

Chronic Phase ◽

Network Connectivity ◽

Pediatric Traumatic Brain Injury ◽

Motor Network

Download Full-text

Motor imagery after stroke: Relating outcome to motor network connectivity

Annals of Neurology ◽

10.1002/ana.21810 ◽

2009 ◽

Vol 66 (5) ◽

pp. 604-616 ◽

Cited By ~ 158

Author(s):

Nikhil Sharma ◽

Jean-Claude Baron ◽

James B. Rowe

Keyword(s):

Motor Imagery ◽

Network Connectivity ◽

Motor Network

Download Full-text

The effects of transcranial direct current stimulation on corticospinal and cortico-cortical excitability and response variability: conventional versus high-definition montages

10.1101/2020.03.30.017046 ◽

2020 ◽

Cited By ~ 1

Author(s):

Michael Pellegrini ◽

Maryam Zoghi ◽

Shapour Jaberzadeh

Keyword(s):

Direct Current ◽

Transcranial Direct Current Stimulation ◽

Primary Motor Cortex ◽

Cortical Excitability ◽

Motor Evoked Potentials ◽

Short Interval ◽

Individual Variability ◽

Response Variability ◽

Pulse Interval ◽

Direct Current Stimulation

AbstractResponse variability following transcranial direct current stimulation (tDCS) highlights need for exploring different tDCS electrode montages. This study compared corticospinal excitability (CSE), cortico-cortical excitability and intra-individual variability following conventional and HD anodal (a-tDCS) and cathodal (c-tDCS) tDCS. Fifteen healthy young males attended four sessions at least one-week apart: conventional a-tDCS, conventional c-tDCS, HD-a-tDCS, HD-c-tDCS. TDCS was administered (1mA, 10-minutes) over the primary motor cortex (M1), via 6×4cm active and 7×5cm return electrodes (conventional tDCS) and 4×1 ring-electrodes 3.5cm apart in ring formation around M1 (HD-tDCS). For CSE, twenty-five single-pulse transcranial magnetic stimulation (TMS) peak-to-peak motor evoked potentials (MEP) were recorded at baseline, 0-minutes and 30-minutes post-tDCS. For cortico-cortical excitability, twenty-five paired-pulse MEPs with 3-millisecond (ms) inter-pulse interval (IPI) and twenty-five at 10ms assessed short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) respectively. MEP standardised z-values standard deviations represented intra-individual variability. No significant differences were reported in CSE between conventional and HD a-tDCS, but significant differences between conventional and HD c-tDCS 0-minutes post-tDCS. Intra-individual variability was significantly reduced in conventional tDCS compared to HD-tDCS for a-tDCS (0-minutes) and c-tDCS (30-minutes). No significant changes were reported in SICI and ICF. These novel findings highlight current technical issues with HD-tDCS, suggesting future tDCS studies should utilise conventional tDCS to minimise intra-individual variability, ensuring tDCS after-effects are true changes in CSE and cortico-cortical excitability.

Download Full-text