Electrical stimulation of the hypothalamus, basal ganglia or pedunculopontine nucleus in decorticate animals results in locomotion and a cardiorespiratory response resembling that seen during exercise. This has led to the hypothesis that parallel activation of cardiorespiratory and locomotor systems from the midbrain could form part of the 'central command' mechanism of exercise. However, the degree to which subcortical structures play a role in cardiovascular activation in awake humans has not been established. We studied the effects on heart rate (HR) and mean arterial blood pressure (MAP) of electrically stimulating the thalamus and basal ganglia in awake humans undergoing neurosurgery for movement disorders (n = 13 Parkinson's disease, n = 1 myoclonic dystonia, n = 1 spasmodic torticollis). HR and MAP increased during high frequency (> 90 Hz) electrical stimulation of the thalamus (HR 5 ± 3 beats min _1 , P = 0.002, MAP 4 ± 3 mmHg, P = 0.05, n = 9), subthalamic nucleus (HR 5 ± 3 beats min _1 , P = 0.002, MAP 5 ± 3 mmHg, P = 0.006, n = 8) or substantia nigra (HR 6 ± 3 beats min _1 , P = 0.001, MAP 5 ± 2 mmHg, P = 0.005, n = 8). This was accompanied by the facilitation of movement, but without the movement itself. Stimulation of the internal globus pallidus did not increase cardiovascular variables but did facilitate movement. Low frequency (< 20 Hz) stimulation of any site did not affect cardiovascular variables or movement. Electrical stimulation of the midbrain in awake humans can cause a modest increase in cardiovascular variables that is not dependent on movement feedback from exercising muscles. The relationship between this type of response and that occurring during actual exercise is unclear, but it indicates that subcortical command could be involved in 'parallel activation' of the locomotor and cardiovascular systems and thus contribute to the neurocircuitry of 'central command'.

Motor cortex stimulation is increasingly reported in the literature as a surgical option for the alleviation of neuropathic pain. The authors review the published literature and present their results including those demonstrated in a randomized controlled trial that confirmed the efficacy of the procedure. Patient selection and prediction of outcomes, however, remain difficult issues.