Dr James Stinear DC, Ph.D.
Dr Stinear gained his Ph.D. from the University of Auckland New Zealand before completing a Post-doctoral Fellowship at SMPP. His early research examined intracortical and spinal level motor system plasticity induced by rhythmic bilateral upper limb movements. He demonstrated that after 4-weeks of synchronized bilateral rhythmic wrist flexion-extension (1 hour per day), the asymmetry in stroke patients’ between-hemisphere cortical excitability was reduced and was associated with improved paretic upper limb function.
His current research is focused on developing a stimulation adjuvant to walking re-training post-stroke. There are three non-invasive techniques that have been used to modulate the excitability of human motor cortex. The first is paired associative stimulation (PAS) which is based on the well established principle of spike-timing-dependent plasticity. The second is repetitive transcranial magnetic stimulation (rTMS) where high frequency (e.g., 5 Hz) stimulation increases, and low frequency (1 Hz) stimulation decreases cortical excitability. The third is transcranial direct current stimulation where low voltage current at ~ 1.0 mA is applied via electrolyte soaked sponge electrodes placed on the scalp over motor cortex.
Dr Stinear pioneered the application of PAS to lower limb cortex during walking (Stinear & Hornby, 2005). The modulation of lower limb motor excitability was consistent with the principles of spike-timing-dependent plasticity, i.e., the modulation was rapidly forming, temporally dependent, persistent, yet reversible. He found that PAS-induced modulation of tibialis anterior during walking was strongly dependent on the phase of the step cycle (Prior & Stinear, 2006). PAS also increases lower limb motor system excitability when applied while the subject is at rest and excitability measures are taken during a post-PAS period of walking (Jayaram, Santos & Stinear, 2007). A recent study revealed that inhibitory PAS applied to the lower limb representations of stroke subjects’ contralesional motor cortex results in the up-regulation of the ipsilesional motor cortex (Jayaram and Stinear, submitted). Studies to assess PAS and rTMS as candidate adjuvants to walking re-training, and to upper limb functional recovery, are planned. Preliminary studies indicate that low frequency rTMS applied to the contralesional motor cortex of stroke subjects induces an up-regulation of ipsilesional motor system excitability to ankle and knee flexors and extensors, in a similar manner to the PAS induced modulation demonstrated in tibialis anterior.