Cortical Excitability During Arm Cycling: A TMS Perspective

Locomotor outputs, such as walking or cycling, require minimal conscious effort and are largely controlled by spinal networks (i.e., central pattern generators or CPGs), with limited involvement from the cortex. In cats, significant cortical activity is primarily observed during locomotion when obstacle avoidance is necessary, suggesting that the cortex has a supporting role. In humans, although spinal CPGs are acknowledged to contribute to locomotor outputs, descending inputs from the motor cortex are considered to play a more significant role than in nonhuman animals. Despite the recognized importance of the cortex in producing locomotor behaviors, surprisingly little is known about how cortical circuitry is involved. Here we discuss our work aimed at examining the cortical control of a locomotor output, arm cycling, using transcranial magnetic stimulation techniques.