Identification of higher brain centres that may encode the cardiorespiratory response to exercise in humans

1. Positron emission tomography (PET) was used to identify the neuroanatomi cal correlates underlying 'central command' during imagination of exercise under hypnosis, in order to uncouple central command from peripheral feedba ck. 2. Three cognitive conditions were used: condition I, imagination of freewh eeling downhill on a bicycle (no change in heart rate, HR, or ventilation, (V) over dot(I)): condition II, imagination of exercise, cycling uphill (in creased HR by 12 % and (V) over dot(I) by 30 % of the actual exercise respo nse): condition III, volitionally driven hyperventilation to match that ach ieved in condition II (no change in HR). 3. Subtraction methodology created contrast A (II minus I) highlighting cer ebral areas involved in the imagination of exercise and contrast B (III min us I) highlighting areas activated in the direct volitional control of brea thing (n = 4 for both; 8 scans per subject). End-tidal P-CO2 (P-ET,P-CO2) w as held constant throughout PET scanning. 4. In contrast 8, significant activations were seen in the right dorso-late ral prefrontal cortex, supplementary motor areas (SMA), the right premotor area (PMA), superolateral sensorimotor areas, thalamus, and bilaterally in the cerebellum. In contrast B, significant activations were present in the SMA and in lateral sensorimotor cortical areas. The SMA/PMA, dorso-lateral prefrontal cortex and the cerebellum are concerned with volitional/motor co ntrol, including that of the respiratory muscles. 5. The neuroanatomical areas activated suggest that a significant component of the respiratory response to 'exercise', in the absence of both movement feedback and an increase in CO2 production, can be generated by what appea rs to be a behavioural response.