Indirect evidence that the motor cortex and the corticospinal tract contribute

Indirect evidence that the motor cortex and the corticospinal tract contribute to the control of walking in human subjects has been provided in previous studies. steady-state treadmill walking. Key points It is often assumed that automatic movements such as walking require little conscious attention and it has therefore been argued that these movements require little cortical control. In humans, however, the gait function is often heavily impaired or completely lost following cortical lesions such as stroke. In this study we investigated synchrony between cortical signals recorded with electroencephalography (EEG) and electromyographic signals (EMG activity) recorded from Rabbit polyclonal to BMPR2 the tibialis anterior muscle (TA) during walking. We found evidence of synchrony in the frequency domain (coherence) between the primary motor cortex and the TA muscle indicating a cortical involvement in human gait function. This finding underpins the importance of restoration of the activity and connectivity between the motor cortex and the spinal cord in the recovery of gait function in patients with damage of the central nervous system. Introduction It is often assumed that cortical activity during a movement implies deliberate conscious control, whereas subcortical and spinal networks are PHA-793887 responsible for automatic movements that require little conscious attention. From this point of view, undemanding steady-state walking would be expected to involve little cortical activity and this is indeed also what has been seen in cats (Armstrong, 1988). Significant cortical activity is only observed when the cat walks in a challenging environment or when forced to step over obstacles (Armstrong, 1988; Armstrong & Marple-Horvat, 1996; Drew 2004, 2008). The PHA-793887 motor cortex in the cat and other animals has therefore been suggested PHA-793887 to play only a facultative role during walking (Armstrong, 1988) However, an increasing number of electrophysiological and imaging studies have provided evidence that the motor cortex may play a more significant role during undemanding steady-state walking in humans. Using imaging techniques such as single-photon emission tomography (SPECT) and near-infrared spectroscopy (NIRS) significant activation is thus observed in the sensorimotor cortex during both real and imagined walking (Fukuyama 1997; Miyai 2001). Experiments using transcranial magnetic stimulation (TMS) have also demonstrated that the corticospinal tract is easily excited throughout the gait cycle (Schubert 1997; Petersen 1998, 2001; Capaday 1999). Petersen (2001) also demonstrated that weak TMS may depress the EMG activity from the active muscles during walking and argued that this depression was caused by removal of the corticospinal contribution to the ongoing EMG activity. All of this evidence is indirect and/or confounded by the necessity of applying external perturbing stimuli. More conclusive evidence would require the application of methodology similar to that used in animal experiments, where functional connectivity between recordings of individual or populations of corticospinal cells and motor output can be demonstrated during the performance of motor behaviours via techniques such as spike-triggered averaging. EMG averages constructed from the discharges of corticospinal neurones in behaving animals not only reveal the presence of anatomical projections, but can also illustrate the extent to which the corticospinal input contributes to the generation of the motor behaviour being studied (Fetz & Cheney, 1987; Lemon, 1993). This approach is evidently not possible in humans, but time (cross-correlation) and frequency (coherence) domain techniques for the detection of coupling between signals provides a convenient analytical framework from which functional coupling between localised cortical activity (measured by MEG or EEG) and motor output (EMG) can be identified in human subjects (Halliday.

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