SUMMARY1. To determine if negative upper airway pressure causes reflex pharyngeal dilator muscle activation, we used intra-oral bipolar surface electrodes to record genioglossus electromyogram (EMG) activity in response to 500 ms duration pressure stimuli of 0. -25.-5.-15, -25 and -35 cmH2O (0-90 % rise time < 30 ms) in ten normal, conscious, supine subjects.2. WN&ith the subjects relaxed at end-expiration, stimuli were applied in each of three conditions: (i) glottis open (GO), (ii) glottis closed (GC) and (iii) controls with the mouth and nose closed.3. Six rectified and integrated EMG responses were bin averaged for each pressure in each experimental condition. Response latency was defined as the time when the EMG activity significantly increased above pre-stimulus levels. Response magnitude was quantified as the ratio of the EMG activity for 80 ms post-stimulus to 80 ms prestimulus; data from after the subject's voluntary reaction time (for tongue protrusion) were not analysed.4. Negative airway pressure activated the genioglossus. The median latency of activation (34 ms) was much faster than the time for voluntary activation (184 ms) indicating a reflex response.5. Significant activation, compared to 0 cmH20 controls and controls with mouth and nose closed, occurred with pressures of at least -5 cmH2O (GC) and -15 cmH2O (GO). , responses with GO were significantly greater than with GC.6. The magnitude ('strength') of the responses differed between subjects; these differences were repeatable.7. WTe conclude that negative airway pressure causes reflex pharyngeal dilator muscle activation in man. Responses with GC suggest that upper airway receptors can mediate the response but larger responses with GO indicate a contribution from subglottal receptors.

A simple model to characterize sympathetic and parasympathetic effects on heart rate (R) was tested during rest in 10 nonathletes and 8 world-class oarsmen. The model states that R = mnR0, where R0 is the intrinsic cardiac rate, and m and n depend only on sympathetic and parasympathetic activity, respectively. The multipliers, m and n, were determined by dual pharmacological blockade in two sessions under similar conditions, but in one session propranolol and in the other atropine was given first. In agreement with the model, when corrections were made for atropine-induced blood pressure changes, m and n did not depend on which blocking agent was administered first. In athletes the control heart rate [55 +/- 3.3 (SD) beats/min] and R0 (81 +/- 8.3 beats/min) were lower than in nonathletes (62 +/- 6.0, P less than 0.01 and 102 +/- 11, P less than 0.001, respectively). The sympathetic multiplier, m, was similar (1.18 +/- 0.06 vs. 1.20 +/- 0.05, P greater than 0.4) in the two groups, but n, the parasympathetic multiplier, was closer to 1 in the athletes (0.57 +/- 0.03 vs. 0.51 +/- 0.05, P less than 0.01). We conclude that the model is suitable for the quantitative study of sympathetic/parasympathetic heart rate control in humans, and that the lower resting heart rate in oarsmen is solely due to a reduction in intrinsic cardiac rate, and not to an increase in parasympathetic tone.

SUMMARY1. To determine the afferent pathways mediating pharyngeal dilator muscle activation in response to negative airway pressure in man, we recorded genioglossus electromyogram (EMG) activity (via intra-oral bipolar surface electrodes) in response to 500 ms duration pressure stimuli of -15 and -25 cmH20 in normal, conscious, supine subjects relaxed at end-expiration; responses were compared before and after upper airway anaesthesia.2. Six rectified and integrated EMG responses were bin averaged for pressure stimuli applied with the glottis open (GO) and closed (GC) and to the outside of the face only (controls). Response magnitude was quantified as the ratio of the EMG activity for an 80 ms post-stimulus period (before the subject's reaction time for tongue protrusion) to an 80 ms pre-stimulus period.3. In eight subjects, upper airway anaesthesia reduced the EMG responses with GC to a level indistinguishable from controls. After anaesthesia, responses with GO remained higher than those with GC.4. With GC, the mean EMG responses decreased by 43 % after selective anaesthesia of the nasal mucosa (trigeminal nerves) in two subjects, 32 % after selective anaesthesia of the laryngeal mucosa (superior laryngeal nerves) in six subjects and by 21 % after selective anaesthesia of the oropharyngeal mucosa (glossopharyngeal and lingual nerves) in four subjects.5. We conclude that upper airway afferents mediate pharyngeal dilator muscle activation in response to negative pressure with GC and that subglottal receptors cause the increased activation with GO. With GC, the trigeminal and superior laryngeal nerves mediate an important component of the responses with the glossopharyngeal nerves playing a less important role.

1. Positron emission tomography (PET) was used to identify the neuroanatomical correlates underlying 'central command' during imagination of exercise under hypnosis, in order to uncouple central command from peripheral feedback.2. Three cognitive conditions were used: condition I, imagination of freewheeling downhill on a bicycle (no change in heart rate, HR, or ventilation, V I ): condition II, imagination of exercise, cycling uphill (increased HR by 12 % and V I by 30 % of the actual exercise response): condition III, volitionally driven hyperventilation to match that achieved in condition II (no change in HR).3. Subtraction methodology created contrast A (II minus I) highlighting cerebral areas involved in the imagination of exercise and contrast B (III minus I) highlighting areas activated in the direct volitional control of breathing (n = 4 for both; 8 scans per subject). End-tidal P CO 2 (P ET,CO 2 ) was held constant throughout PET scanning.4. In contrast A, significant activations were seen in the right dorso-lateral 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 control, 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 CO 2 production, can be generated by what appears to be a behavioural response.

We have defined areas in the brain activated during speaking, utilizing positron emission tomography. Six normal subjects continuously repeated the phrase "Buy Bobby a poppy" (requiring minimal language processing) in four ways: A) spoken aloud, B) mouthed silently, C) without articulation, and D) thought silently. Statistical comparison of images from conditions A with C and B with D highlighted areas associated with articulation alone, because control of breathing for speech was controlled for; we found bilateral activations in sensorimotor cortex and cerebellum with right-sided activation in the thalamus/caudate nucleus. Contrasting images from conditions A with B and C with D highlighted areas associated with the control of breathing for speech, vocalization, and hearing, because articulation was controlled for; we found bilateral activations in sensorimotor and motor cortex, close to but distinct from the activations in the preceding contrast, together with activations in thalamus, cerebellum, and supplementary motor area. In neither subtraction was there activation in Broca's area. These results emphasize the bilaterality of the cerebral control of "speaking" without language processing.