Author name cluster

J.C. Rothwell

Possible papers associated with this exact author name in Arrow. This page groups case-insensitive exact name matches and is not a full identity disambiguation profile.

4 papers

1 author row

YNICL Journal 2017 Journal Article

Time-dependent functional role of the contralesional motor cortex after stroke

L.J. Volz
M. Vollmer
J. Michely
G.R. Fink
J.C. Rothwell
C. Grefkes

After stroke, movements of the paretic hand rely on altered motor network dynamics typically including additional activation of the contralesional primary motor cortex (M1). The functional implications of contralesional M1 recruitment to date remain a matter of debate. We here assessed the role of contralesional M1 in 12 patients recovering from a first-ever stroke using online transcranial magnetic stimulation (TMS): Short bursts of TMS were administered over contralesional M1 or a control site (occipital vertex) while patients performed different motor tasks with their stroke-affected hand. In the early subacute phase (1–2weeks post-stroke), we observed significant improvements in maximum finger tapping frequency when interfering with contralesional M1, while maximum grip strength and speeded movement initiation remained unaffected. After >3months of motor recovery, disruption of contralesional M1 activity did not interfere with performance in any of the three tasks, similar to what we observed in healthy controls. In patients with mild to moderate motor deficits, contralesional M1 has a task- and time-specific negative influence on motor performance of the stroke-affected hand. Our results help to explain previous contradicting findings on the role of contralesional M1 in recovery of function.

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YNIMG Journal 2008 Journal Article

Neural correlates of age-related changes in cortical neurophysiology

P. Talelli
A. Ewas
W. Waddingham
J.C. Rothwell
N.S. Ward

Functional imaging studies of cortical motor systems in humans have demonstrated age-related reorganisation often attributed to anatomical and physiological changes. In this study we investigated whether aspects of brain activity during a motor task were influenced not only by age, but also by neurophysiological parameters of the motor cortex contralateral to the moving hand. Twenty seven right-handed volunteers underwent functional magnetic resonance imaging whilst performing repetitive isometric right hand grips in which the target force was parametrically varied between 15 and 55% of each subject’s own maximum grip force. For each subject we characterised two orthogonal parameters, B G (average task-related activity for all hand grips) and B F (the degree to which task-related activity co-varied with peak grip force). We used transcranial magnetic stimulation (TMS) to assess task-related changes in interhemispheric inhibition from left to right motor cortex (IHIc) and to perform measures relating to left motor cortex excitability during activation of the right hand. Firstly, we found that B G in right (ipsilateral) motor cortex was greater with increasing values of age2 and IHIc. Secondly, B F in left ventral premotor cortex was greater in older subjects and in those in whom contralateral M1 was less responsive to TMS stimulation. In both cases, neurophysiological parameters accounted for variability in brain responses over and above that explained by ageing. These results indicate that neurophysiological markers may be better indicators of biological ageing than chronological age and point towards the mechanisms by which reconfiguration of distributed brain networks occurs in the face of degenerative changes.

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YNIMG Journal 2002 Journal Article

Parietal Magnetic Stimulation Delays Visuomotor Mental Rotation at Increased Processing Demands

S. Bestmann
K.V. Thilo
D. Sauner
H.R. Siebner
J.C. Rothwell

Visuomotor rotation (VMR) is a variant of the classic mental rotation paradigm. Subjects perform a center-out arm reaching movement, with the instruction to point clockwise or anticlockwise away from the direction of a reaction signal by a prespecified amount. Like classic mental rotation (MR) tasks, there is a linear relationship between reaction time (RT) and required angle of rotation (angular disparity). Although functional imaging studies have consistently demonstrated parietal activations centered around the intraparietal sulcus during MR tasks, the involvement of parietal cortex in VMR has not been investigated. The aim of the present experiments was to test in human subjects whether VMR also involves activity in parietal areas. We used short trains of transcranial magnetic stimulation (TMS) to produce a temporary “virtual lesion” of the posterior parietal cortex (PPC) around the intraparietal sulcus during the reaction period of a VMR task. Four pulses of 20-Hz rTMS were applied to the left PPC, right PPC, or vertex (control condition) 100 ms after the presentation of an instruction cue. Reaction times (RTs) were evenly prolonged by right or left parietal TMS compared with vertex stimulation, but only for large angles of rotation, and without affecting the spatial accuracy of the final response. A control experiment showed that parietal rTMS did not impair visual perception or the ability to judge the size of visual angles. The data thus provide evidence for bilateral involvement of the PPC in VMR that increases with processing demands.

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YNIMG Journal 2001 Journal Article

TMS Produces Two Dissociable Types of Speech Disruption

L. Stewart
V. Walsh
U. Frith
J.C. Rothwell

We aimed to use repetitive transcranial magnetic stimulation (rTMS) to disrupt speech with the specific objective of dissociating speech disruption according to whether or not it was associated with activation of the mentalis muscle. Repetitive transcranial magnetic stimulation (rTMS) was applied over two sites of the right and left hemisphere while subjects counted aloud and recited the days of the week, months of the year, and nursery rhymes. Analysis of EMG data and videotaped recordings showed that rTMS applied over a posterior site, lateral to the motor hand area of both the right and the left hemisphere resulted in speech disruption that was accompanied by activation of the mentalis muscle, while rTMS applied over an anterior site on the left but not the right hemisphere resulted in speech disruption that was dissociated from activation of the mentalis muscle. The findings provide a basis for the use of subthreshold stimulation over the extrarolandic speech disruption site in order to probe the functional properties of this area and to test psychological theories of linguistic function.

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