Proceedings of The Physiological Society
University College London December 2005 (2006) Proc Physiol Soc 1, PC17
Mapping the cortical representation of the lumbar paravertebral muscles in humans
O'Connell, Neil E; Maskill, David W; Cossar, John; Nowicky, Alex V;
1. Centre for Research in Rehabilitation, Brunel University, Middlesex, United Kingdom.
Cortical maps of muscle representations provide a tool for investigating neuroplastic changes in response to a variety of stimuli and insults. While stimulation of the cortex with TMS has identified contralateral and ipsilateral corticospinal projections to trunk muscles, to date comprehensive maps of the representation of the lumbar paravertebral muscles have not been demonstrated. The aim of this study was to investigate the feasibility of constructing maps of the cortical representation of the lumbar paravertebral muscles in normal healthy subjects using transcranial magnetic stimulation (TMS). Twelve normal healthy volunteers were investigated. While subjects maintained a steady level of activity in the lumbar paravertebral muscles with a forward sitting manoeuvre, TMS stimuli were applied using a biphasic Magstim stimulator to reference points on a grid applied on the cranium over the left motor cortex. Six stimuli were applied to each reference point. Using surface electromyography, motor evoked potentials (MEPs) in the lumbar erector spinae (ES) and superficial multifidus (SM) muscles were recorded bilaterally in response to these stimuli. Responses obtained from each grid point were averaged and MEP area was calculated. Responses were normalised for each subject by expressing MEP area for all stimulation sites as a percentage of the peak response. Centre of gravity (COG) was calculated using the formula presented by Wassermann et al. (1992): COG = [
Where applicable, experiments conform with Society ethical requirements