Respiratory sinus arrhythmia (RSA), systolic and diastolic respiratory blood pressure waves (RBPWsyst, RBPWdiast), mean heart rate (HR), mean respiratory frequency (RF) and the heart beat to respiratory cycle ratio (HB/RC) were measured in 23 spontaneously breathing, normotensive or renal hypertensive dogs under light anaesthesia. No significant differences were found between conditions of normal and chronically elevated blood pressure. All these parameters were analyzed statistically by means of linear regression analysis and rank correlation coefficient (rs). A correlation was found to exist between RSA and mean systolic blood pressure (negative), RF (negative), RBPWsyst (positive), RBPWdiast (positive). RF correlated with both HB/RC (negative) and RBPWsyst (negative). A correlation was also seen between PA and both BPsyst (positive) and BPdiast (positive), BPsyst and BPdiast (positive) and between HR and RBPWdiast (negative); however, all the remaining, theoretically possible correlations were not significant. The results may be referred to resonance mechanisms in a common nervous oscillator system. 相似文献
For isometric tasks, shoulder muscle forces are assumed to scale linearly with the external arm load magnitude, i.e., muscle
force ratios are constant. Inverse dynamic modeling generally predicts such linear scaling behavior, with a critical role
for the arbitrary load sharing criteria, i.e., the “cost function”. We tested the linearity of the relation between external
load magnitude exerted on the humerus and shoulder muscle activation. Six isometric force levels ranging from 17 to 100% of
maximal arm force were exerted in 24 directions in a plane perpendicular to the longitudinal axis of the humerus. The direction
of maximum muscle activation, the experimentally observed so called Principal Action (PA), was determined for each force magnitude
in 12 healthy subjects. This experiment was also simulated with the Delft Shoulder and Elbow Model (DSEM) using two cost functions:
(1) minimizing muscle stress and (2) a compound, energy related cost function. PA, both experimental (PAexp) and simulated (PAsim), was expected not to change with arm forces magnitudes. PAexp of the mm. trapezius pars descendens, deltoideus pars medialis and teres major changed substantially as a function of external
force magnitude, indicating external load dependency of shoulder muscle activation. In DSEM simulations, using the stress
cost function, small non-linearities in the muscle force–external load dependency were observed, originating from gravitational
forces working on clavicular and scapular bone masses. More pronounced non-linearities were introduced by using the compound
energy related cost function, but no similarity was observed between PAexp and PAsim. 相似文献
When reaching for an object we usually look at it before we touch it with the hand. This often unconscious eye movement prior to the arm movement allows guiding of the final part of the hand trajectory by visual feedback. We examined the temporal and spatial coordination of this control system by psychophysical measurements of eye and arm movements of naive human subjects looking or looking and pointing as fast as possible to visual targets in physical and virtual-reality setups. The reaction times of saccades to a step-displaced target were reduced, and the number of corrective saccades decreased, when the subject had to produce a corresponding simultaneous hand movement to the same target. The saccadic reaction time was increased when saccade and hand movement went in opposite directions. In a double-step task the reaction time for the second saccade was longer than for the first. Co-use of the hand leads to an additional increase of saccadic reaction time. Taken together this study shows an improvement in initial saccades if they are accompanied by hand movements to the same target. This effect might ensure that the reach target is foveated early and accurately enough to support the visual feedback control of the hand near the target. Longer reaction times for the second saccade to double-step displaced targets might reflect a saccadic refractory time intensified by simultaneous arm movements. These results are discussed in the light of recent findings from our laboratory on saccade- and reach-related neurons in the superior colliculus of macaque monkeys. 相似文献
Chewing, swallowing, breathing, and vocalization in mammals require precise coordination of tongue movements with concomitant activities of the mimetic muscles. The neuroanatomic basis for this oro-facial coordination is not yet fully understood. After the stereotaxic microinjection of retrograde and anterograde neuronal tracers (biotin-dextran, Fluoro-Ruby, Fluoro-Emerald, and Fluoro-Gold) into the facial and hypoglossal nuclei of the rat, we report here a direct bilateral projection of hypoglossal internuclear interneurons onto facial motoneurons. We also confirm the existence of a small pool of neurons in the dorsal part of the brainstem reticular formation that project ipsilaterally to both facial and hypoglossal nuclei. For precise tracer injections, both motor nuclei were located and identified by the electrical antidromic activation of their constituent motoneurons. Injections of retrograde tracers into the facial nucleus consistently labeled neurons in the hypoglossal nucleus. These neurons prevalently lay in the ipsilateral side, were small in size, and, like classic intrinsic hypoglossal local-circuit interneurons, had several thin dendrites. Reverse experiments - injections of anterograde tracers into the hypoglossal nucleus - labeled fine varicose nerve fiber terminals in the facial nucleus. These fiber terminals were concentrated in the intermediate subdivision of the facial nucleus, with a strong ipsilateral prevalence. Double injections of different tracers into the facial and the hypoglossal nuclei revealed a small, but constant, number of double-labeled neurons located predominantly ipsilateral in the caudal brainstem reticular formation. Hypoglossal internuclear interneurons projecting to the facial nucleus, as well as those neurons of the parvocellular reticular formation that project to both facial and hypoglossal nuclei, could be involved in oro-facial coordination. 相似文献
OBJECTIVE: To suggest an empirically based school entry screening examination for the detection of deficits in attention, motor control and perception (DAMP) in 6-y-old children. MATERIAL AND METHODS: A population-based cohort of 113 children, 6-7 y of age (62 with and 51 without DAMP), compared on measures of attention, motor functions, language and cognition. RESULTS: Attention deficits were convincingly identified by both parents and paediatrician. The motor function tests clearly distinguished between the two groups. Linguistic and meta-linguistic tests demonstrated greater phonological processing difficulties in the DAMP group. The cognitive test revealed an overall lower IQ but no consistent characteristic pattern in the DAMP group. CONCLUSIONS: A simplified paediatric school entry examination test is suggested. Four motor tests (standing on one foot, Fog test, design copying and diadochokinesis) administered by the paediatrician, combined with a brief structured clinical observation and a structured parent interview, identified 80% of children with DAMP-and all those with severe DAMP-as well as a small number of false positives. 相似文献
Summary: Homopolymerization of 4‐methyl‐1,3‐pentadiene (MP) and copolymerization of 4‐methyl‐1,3‐pentadiene with alkenes (ethylene, 1‐pentene, 4‐methyl‐1‐pentene) were performed to investigate the effect of the so‐called backbiting coordination on the chemoselectivity of 1,3‐diene polymerization. Three homogeneous catalyst systems were used: CpTiCl3‐MAO, Cp2TiCl2‐MAO and Cp2TiCl‐MAO. Backbiting coordination is possible with the first catalyst, but not with the other two. The three catalysts gave similar results, which indicates that backbiting has no effect on the polymerization chemoselectivity, contrary to what has been reported in recent literature. An interpretation is presented for the formation of 1,4 units in MP/alkene copolymers. This interpretation is based on the fact that allyl groups have predominantly a syn configuration in MP homopolymerization, whereas allyl groups of anti configuration are formed in MP/alkene copolymerization. The role of backbiting in diene polymerization is discussed.
The effect of anti/syn isomerism on the chemoselectivity in the different polymerizations. 相似文献