Continuous passive movement does not influence motor maps in healthy adults

Hand weakness following stroke is often associated with a reduced representation of the hand in the primary motor cortex. Meaningful sensory input can induce sensorimotor reorganization in the brain, but the after-effect of continuous passive motion (CPM) on the cortical representation is unknown. The purpose of this study was to determine whether repeated sessions of continuous passive movement of the thumb induce a lasting increase in the motor cortical representation of a thumb muscle in healthy adults. Thirteen right-handed healthy adults (mean age 24.3 ± 4.3 years) participated in the study. Single-pulse Transcranial Magnetic Stimulation (TMS) was delivered over the motor area of the target muscle (abductor pollicis brevis) before and/or after a thirty minute session of thumb CPM administered on three consecutive days. TMS was also delivered 5 days after cessation of the CPM intervention. The response to TMS (motor evoked potential) was recorded in the target muscle with surface EMG. Resting motor threshold (RMT), motor evoked potential amplitude at a specified intensity, and the area and volume of the cortical representation of the target muscle were measured. Thumb CPM had no significant effect on TMS parameters (p > 0.05 all measures) and performance of an attention task remained unchanged within and across CPM sessions. The results suggest that three sessions of repetitive passive thumb movement is not sufficient to induce a change in the cortical representation of the thumb and is unlikely to reverse the decreased representation of the affected hand following stroke.Michelle N. McDonnell, Susan L. Hillier, George M. Opie, Matthew Nowosilskyj, Miranda Haberfield, and Gabrielle Tod

Critical Reynolds number for nonlinear flow through rough-walled fractures: The role of shear processes

This paper experimentally investigates the role of shear processes on the variation of critical Reynolds number and nonlinear flow through rough-walled rock fractures. A quantitative criterion was developed to quantify the onset of nonlinear flow by comprehensive combination of Forchheimer's law and Reynolds number. At each shear displacement, several high-precision water flow tests were carried out with different hydraulic gradients then the critical Reynolds number was determined based on the developed criterion. The results show that (i) the Forchheimer's law was fitted very well to experimental results of nonlinear fluid flow through rough-walled fractures, (ii) the coefficients of viscous and inertial pressure drops experience 4 and 7 orders of magnitude reduction during shear displacement, respectively, and (iii) the critical Reynolds number varies from 0.001 to 25 and experiences 4 orders of magnitude enlargement by increasing shear displacement from 0 to 20 mm. These findings may prove useful in proper understanding of fluid flow through rock fractures, or inclusions in computational studies of large-scale nonlinear flow in fractured rocks