Natural history of sucking patterns in infant goats: A comparative study.

Examined temporal organization of sucking patterns, the phase interaction of sucking and other rhythmical motor patterns, and the effects of feeding on sucking rate in 26 Nubian goats. No changes in sucking rate were noted over the 1st 3 mo. The precise rate concordance between sucking and tail movements suggested that peripheral motor rhythms are regulated by a central sequencing mechanism which in turn is modulated by organismic and peripheral factors. A comparison of sucking patterns in 10 human infants and Ss indicates that qualitative species differences in the prefunctional organization of sucking influence the nature of the interaction between sucking performance and organismic or peripheral factors. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genesis of spontaneous rhythmic motor patterns in the lumbosacral spinal cord of neonate mouse

The isolated spinal cord of the neonatal mouse spontaneously generates two different motor patterns of continuous rhythmic bursting: one in lumbar ventral roots in earliest postnatal preparations (P0-2) and another at the sacral level at later postnatal times (P3-5). Lumbar rhythmic motor discharges clearly alternate on contralateral roots and are in a frequency range (approximately 1 Hz) usually described for locomotor-like activity, while sacral motor sequences include mixed synchrony and irregular bilateral alternation that differ from typical locomotor-like activity. A significant decrease in the frequency and increase in the duration of spontaneous rhythmic bursts occur between lumbar and sacral motor patterns. In quiescent preparations from both postnatal periods, perfusion with Mg(2+)-free medium systematically induces a rhythmic activity at both lumbar and sacral level. Temporal characteristics of motor patterns under Mg(2+)-free medium are similar to spontaneous rhythms. Activating NMDA receptor channels by diminishing their Mg2+ block appears to be an efficient way of decreasing the threshold for genesis of the spinal rhythm in mouse. Bath application of NMDA and non-NMDA receptor antagonists blocks Mg(2+)-free-induced rhythmic activities in an irreversible or reversible manner, respectively. The effects of Mg(2+)-free medium and of glutamate antagonists provide evidence for the excitatory amino acid (EAA) dependence of both rhythmic motor patterns. Finally, the possibility that the recording of two different motor patterns may reflect a rostrocaudal developmental process is discussed.     

Long-term registration of cutaneous microcirculation during general anesthesia

The temporal dynamics of the systemic arterial pressure can be monitored noninvasively from the skin of the earlobe or forehead by photoplethysmography under the provision that the active control of the microcirculatory perfusion is eliminated. Using this approach, we have been able to detect a highly stable blood pressure rhythm in the range of 0.15 Hz during psychophysical relaxation or sleep. The aim of the present study was to investigate the occurrence and behavior of blood pressure rhythms below 0.2 Hz during general anesthesia. In 30 patients (ASA groups I-II) undergoing basic surgical procedures, photoplethysmographic recordings from the earlobe were made during the whole time of anesthesia. The recorded signals were divided into segments of 200 s of duration, the temporal structure of which was analyzed by fast Fourier transform. Different characteristic patterns of rhythmical behavior were detected: (1) absence of activity below 0.2 Hz ('low-frequency range'); (2) slow sinusoidal rhythmicity below 0.05 Hz; (3) 'chaotic' behavior, i.e. multiple incoherent fluctuations without stationary periods or amplitudes; (4) short-term rhythmical activity at about 0.15 Hz, and (5) long-term rhythmical activity at about 0.15 Hz. In patients sufficiently sedated to eliminate low-frequency activity, rhythmicity could sometimes be triggered by certain surgical stimuli, the response to which was suppressed by injection of opioids. The data presented strongly suggest that rhythmical perfusion patterns of the cutaneous microcirculation could serve as an indicator for the depth of anesthesia.     

The rhythmicity of sympathetic nerve activity

This review focuses on that most engaging feature of the sympathetic nervous system, its rhythmicity. In particular examining the nature of sympathetic nerve activity (SNA), its characteristics, the frequencies of these rhythms and possible mechanisms responsible for their generation. Sympathetic activity can be thought of as a complex output of the central nervous system providing subtle control over end organ function. This control is exerted in a number of frequency bands including rhythms related to the cardiac and respiratory cycles, 10 Hz, and between 0.2 and 0.4 Hz. The generation and control over the occurrence of each of these rhythms is likely to be quite separate. Although afferent feedback from sources such as baroreceptors can explain some of the rhythmical properties in each case there is good evidence for inherent generation of aspects of these rhythms. A variety of brainstem cell groups are thought to be involved in their generation with the rostral ventrolateral medulla, although unlikely to be solely responsible for tone generation, an important regulator of overall activity. SNA also varies in the number of nerves recruited to fire in each synchronized discharge. Little is known about this control other than it appears to be quite separate from the control over the timing of discharges. Spinal cord mechanisms are possibly involved. SNA frequencies above 0.7 Hz do not appear to directly induce oscillations in innervated vasculature, however, are likely to contribute to setting the level of vasconstrictive tone. Slower frequencies appear to directly cause oscillations in blood flow.     

Natural history of global and critical brain ischaemia. Part II: EEG and neurological signs in patients remaining unconscious after cardiopulmonary resuscitation

Of 125 patients who had no detectable cortical activity (DCA) on the electroencephalograph (EEG) immediately upon resuscitation from circulatory arrest of primary cardiovascular aetiology, 88 remained unconscious; these patients had their EEG and neurological status serially investigated until they died. Immediately upon re-establishment of circulation all cerebral functions could be absent; the brain death (irreversible loss of functions) was then signified by the appearance of poikilothermia, diabetes insipidus and reflex extension of the upper limb. Most often, some cranial nerve reflexes were present; the EEG configurations and related neurological signs then appeared in a sequence which resembled orderly postischaemic recovery: A phase without DCA was at first characterized by an exclusive presence of cranial nerve reflexes and then by the appearance of decerebrate posturing this phase was followed by another phase of intermittent cortical activity (ICA) with decorticate and stereotypic motor responses and a phase of continuous cortical activity (CCA) accompanied by stereotypic reactivity. These phases were most often incomplete due to failure of recovery of some cranial nerve reflexes or were abnormal due to the appearance of intermittent spikes and sharp waves. Progressive recovery could stagnate at any step and the cerebral functions be lost abruptly or gradually in reverse order of recovery. The decay was invariably due to cardiovascular or pulmonary complications. Brain autopsy revealed extensive neuronal loss and intravital autolytic changes in patients who had fulfilled clinical criteria of brain death for more than 72 h, but the histopathology showed no relationship to other clinical findings during the postischaemic course.     

Evidence that trigeminal brainstem interneurons form subpopulations to produce different forms of mastication in the rabbit

To determine how trigeminal brainstem interneurons pattern different forms of rhythmical jaw movements, four types of motor patterns were induced by electrical stimulation within the cortical masticatory areas of rabbits. After these were recorded, animals were paralyzed and fictive motor output was recorded with an extracellular microelectrode in the trigeminal motor nucleus. A second electrode was used to record from interneurons within the lateral part of the parvocellular reticular formation (Rpc-alpha, n = 28) and gamma- subnucleus of the oral nucleus of the spinal trigeminal tract (NVspo-gamma, n = 68). Both of these areas contain many interneurons projecting to the trigeminal motor nucleus. The basic characteristics of the four movement types evoked before paralysis were similar to those seen after the neuromuscular blockade, although cycle duration was significantly decreased for all patterns. Interneurons showed three types of firing pattern: 54% were inactive, 42% were rhythmically active, and 4% had a tonic firing pattern. Neurons within the first two categories were intermingled in Rpc-alpha and NVspo-gamma: 48% of rhythmic neurons were active during one movement type, 35% were active during two, and 13% were active during three or four patterns. Most units fired during either the middle of the masseter burst or interburst phases during fictive movements evoked from the left caudal cortex. In contrast, there were no tendencies toward a preferred coupling of interneuron activity to any particular phase of the cycle during stimulation of other cortical sites. It was concluded that the premotoneurons that form the final commands to trigeminal motoneurons are organized into subpopulations according to movement pattern.     

Patterns of eye–hand coordination in the first year of life.

The traditional reflex-to-voluntary behavior model of development is questioned, and an alternative hypothesis is proposed that reflex functions are distinct from the ontogenetic antecedents of voluntary behavior. An overview of patterns of eye–hand coordination in the 1st yr of life suggests that reflexes and cortically controlled instrumental activity share a parallel course of development, with the latter increasing in frequency and importance as development proceeds. Despite procedural problems in studying neonatal reaching there remains sufficient evidence that hand movements in infants under 8 wks of age are progressively coordinated with visual stimuli. Some new data are presented that show that up to at least 12 wks of age the left hand shows greater activity and orientation to visual stimuli than the right hand, which is contralateral to the dominance of neonatal reflexes. Experiments are reviewed that have studied the emergence of visually guided reaching and its development during the 2nd half of the 1st yr. The evidence is consistent with the hypothesis that this apparently new behavior, clearly distinct from reflexes, is in fact on a continuum with these earlier nonreflexive, instrumental behaviors. (French abstract) (79 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Simultaneous changes of rhythmic organization in brainstem neurons, respiration, cardiovascular system and EEG between 0.05 Hz and 0.5 Hz

Several neurons from different regions of the brainstem of anesthetized dogs were simultaneously recorded, together with various parameters of the cardiovascular system, respiration, efferent sympathetic neural activities and cortical activity. Often rhythmic changes of activity in the range 0.05-0.5 Hz could be observed in the simultaneously recorded signals. The rhythms were analysed in time domain and by power spectra and their changes depicted over the time. The most striking rhythms between 0.05 Hz and 0.5 Hz are the respiratory rhythm and those rhythms that originate in reticular neurons of the common brainstem system as well as their respective harmonics, i.e. the ranges around the integer multiple frequencies of these basic rhythms. The observed oscillations can vanish and reappear at times. Frequencies of basic oscillations and harmonics and their amplitudes are subject to distinct slow modulations. These modulations can have irregular as well as regular courses. The different rhythms can appear separately or simultaneously in the single signals. The most important phenomenon to be observed is that the rhythms mutually influence their frequencies, which follows the rules of 'relative coordination' as described by E. v. Holst. Such changes of rhythmic activities generally also concern the ranges of harmonics of the basic rhythms. Rhythmic influences on peripheral functional systems, e.g. the cardiovascular system, are most distinct at times when the different rhythms overlap in their frequency ranges. This holds not only for the ranges of basic frequencies, but also for the ranges of their harmonics. Further it was found that rhythms with the same basic frequencies may not only appear simultaneously, but also at various times in the different functional systems. The temporal course of changes of these rhythms, their interactions and their influence on the processing of cardiac rhythmic neuronal discharge patterns is demonstrated. The meaning of the mutually influencing rhythms for the functional organization of central nervous structures is discussed.     

The functional role of the septum

A study of the electrical activity (background and at sensory stimulation) of the motor and visual areas of the cortex, hippocampus, septum (in some cases the lateral geniculate body and the midbrain reticular formation) was carried out on rabbits by the method of spectral-correlation analysis. The method of driving reactions to electrical stimulation of the lateral and medial nuclei of the septum was used to investigate its functional role as a pace-maker. The spectograms of all the analyzed areas of the brain showed the presence of acquired rhythms during electrical stimulation at 4-30 Hz. The acquired rhythm was most prominent in cortical potentials. It is assumed that the generation of rhythmical cortical activity is due to physiological interaction of the cortex and septum.     

Three-dimensional organization of otolith-ocular reflexes in rhesus monkeys. I. Linear acceleration responses during off-vertical axis rotation

1. The dynamic properties of otolith-ocular reflexes elicited by sinusoidal linear acceleration along the three cardinal head axes were studied during off-vertical axis rotations in rhesus monkeys. As the head rotates in space at constant velocity about an off-vertical axis, otolith-ocular reflexes are elicited in response to the sinusoidally varying linear acceleration (gravity) components along the interaural, nasooccipital, or vertical head axis. Because the frequency of these sinusoidal stimuli is proportional to the velocity of rotation, rotation at low and moderately fast speeds allows the study of the mid-and low-frequency dynamics of these otolith-ocular reflexes. 2. Animals were rotated in complete darkness in the yaw, pitch, and roll planes at velocities ranging between 7.4 and 184 degrees/s. Accordingly, otolith-ocular reflexes (manifested as sinusoidal modulations in eye position and/or slow-phase eye velocity) were quantitatively studied for stimulus frequencies ranging between 0.02 and 0.51 Hz. During yaw and roll rotation, torsional, vertical, and horizontal slow-phase eye velocity was sinusoidally modulated as a function of head position. The amplitudes of these responses were symmetric for rotations in opposite directions. In contrast, mainly vertical slow-phase eye velocity was modulated during pitch rotation. This modulation was asymmetric for rotations in opposite direction. 3. Each of these response components in a given rotation plane could be associated with an otolith-ocular response vector whose sensitivity, temporal phase, and spatial orientation were estimated on the basis of the amplitude and phase of sinusoidal modulations during both directions of rotation. Based on this analysis, which was performed either for slow-phase eye velocity alone or for total eye excursion (including both slow and fast eye movements), two distinct response patterns were observed: 1) response vectors with pronounced dynamics and spatial/temporal properties that could be characterized as the low-frequency range of "translational" otolith-ocular reflexes; and 2) response vectors associated with an eye position modulation in phase with head position ("tilt" otolith-ocular reflexes). 4. The responses associated with two otolith-ocular vectors with pronounced dynamics consisted of horizontal eye movements evoked as a function of gravity along the interaural axis and vertical eye movements elicited as a function of gravity along the vertical head axis. Both responses were characterized by a slow-phase eye velocity sensitivity that increased three- to five-fold and large phase changes of approximately 100-180 degrees between 0.02 and 0.51 Hz. These dynamic properties could suggest nontraditional temporal processing in utriculoocular and sacculoocular pathways, possibly involving spatiotemporal otolith-ocular interactions. 5. The two otolith-ocular vectors associated with eye position responses in phase with head position (tilt otolith-ocular reflexes) consisted of torsional eye movements in response to gravity along the interaural axis, and vertical eye movements in response to gravity along the nasooccipital head axis. These otolith-ocular responses did not result from an otolithic effect on slow eye movements alone. Particularly at high frequencies (i.e., high speed rotations), saccades were responsible for most of the modulation of torsional and vertical eye position, which was relatively large (on average +/- 8-10 degrees/g) and remained independent of frequency. Such reflex dynamics can be simulated by a direct coupling of primary otolith afferent inputs to the oculomotor plant. (ABSTRACT TRUNCATED)     

Differentiation between hepatic cavernous hemangioma and malignant tumor with T2-weighted MRI: comparison of fast spin-echo and breathhold fast spin-echo pulse sequences

An in vitro jaw-attached brainstem preparation was developed to investigate the relationship between jaw opener and closer muscle activity during chemically induced rhythmical jaw movements in neonatal rats. In the majority of preparations examined, where a defined region of brainstem was isolated and the neuronal innervation of the jaw opener and closer muscles was left intact, bath application of the excitatory amino acid agonist N-methyl-D,L-aspartate (NMA, 20-40 microM) in combination with bicuculline (BIC 10 microM), a GABA(A) antagonist, produced rhythmical electromyogram (EMG) activity in jaw opener and closer muscles, bilaterally, in conjunction with rhythmical jaw movements. Low concentrations of NMA (20 microM) in combination with BIC produced temporally coordinated activity between the jaw opener and closer muscles, ipsilaterally. With higher doses of NMA (40 microM), each muscle group exhibited bursting, but temporal coordination between them was difficult to establish. Similarly, NMA application in combination with the glycine antagonist strychnine (STR, 10 microM), also produced rhythmical EMG activity from both opener and closer muscles, ipsilaterally, but showed no temporal coordination between the antagonist muscle pair. However, coordination of opener and closer muscle discharge could be restored by the addition of BIC to the bath. We suggest that there exist separate, but coordinated, rhythm generator circuits for opener and closer motoneuronal discharge located in close proximity to the trigeminal motor nucleus and under GABAergic control for production of temporal coordination between rhythmogenic circuits.     

Extracellular K+ induces locomotor-like patterns in the rat spinal cord in vitro: comparison with NMDA or 5-HT induced activity

Bath-application of increasing concentrations of extracellular K+ elicited alternating motor patterns recorded from pairs of various lumbar ventral roots of the neonatal rat (0-2 days old) spinal cord in vitro. The threshold concentration of K+ for this effect was 7.9 +/- 0.8 mM (mean +/- SD). The suprathreshold concentration range useful to evoke persistent motor patterns (lasting >/=10 min) was very narrow ( approximately 1 mM) as further increments elicited only rhythmic activity lasting from 20 s to a few minutes. On average, the fastest period of rhythmic patterns was 1.1 +/- 0.3 s. Intracellular recording from lumbar motoneurons showed that raised extracellular K+ elicited membrane potential oscillations with superimposed repetitive firing. In the presence of N-methyl--aspartate (NMDA) or non-NMDA receptor blockers [R(-)-2-amino-phosphonovaleric acid or 6-cyano-7-nitroquinoxaline-2,3-dione, respectively] extracellular K+ increases could still induce motor patterns although the threshold concentration was raised. Serotonin (5-HT) also induced alternating motor patterns (threshold 15 +/- 7 microM) that were consistently slower than those induced by high K+ or NMDA. Ritanserin (1 microM) prevented the locomotor-like activity of 5-HT but not that of high K+ provided the concentration of the latter was further increased. Subthreshold concentrations of K+ became effective in the presence of subthreshold doses of 5-HT or NMDA, indicating mutual facilitation between these substances. The fastest pattern frequency was observed by raising K+ or by adding NMDA. In the presence of 5-HT, the pattern frequency was never as fast even if NMDA (or high K+) was coapplied. Furthermore, application of 5-HT significantly slowed down the K+- or NMDA-induced rhythm, an effect strongly potentiated in the presence of ritanserin. It is suggested that the operation of the spinal locomotor network was activated by rises in extracellular K+, which presumably led to a broad increase in neuronal excitability. Whenever the efficiency of excitatory synaptic transmission was diminished (for example by glutamate receptor antagonism), a larger concentration of K+ was required to evoke locomotor-like patterns. The complex effect (comprising stimulation and inhibition) of 5-HT on alternating pattern generation appeared to result from a dual action of this substance on the spinal locomotor network.     

Motor-unit recruitment in self-reinnervated muscle

1. Recruitment order of motor units in self-reinnervated medial gastrocnemius (MG) muscles was studied in decerebrate cats 16 mo after surgical reunion of the cut MG nerve. Pairs of MG motor units were isolated by dual microelectrode penetration of ventral roots to measure their recruitment sequence during cutaneous reflexes in relation to their physiological properties. 2. Physiological properties of reconstituted motor units appeared normal, as expected. Also normal were the relationships among these properties: twitch and tetanic tension tended to increase with axonal conduction velocity and decrease with twitch contraction time. A small fraction of motor units (10/116) in reinnervated muscles produced either no measurable tension or unusually large amounts of tension compared with controls. This was the only distinct feature of the sample of reconstituted units. 3. In muscles reinnervated after nerve section, stretch was notably ineffective in eliciting reflex contraction of MG muscles or their constituent motor units (only 5/116 units). Incomplete recovery from nerve section was probably the cause of this impairment, because stretch reflexes were readily evoked in adjacent untreated muscles and in one reinnervated MG muscle that was studied 16 mo after nerve crush. In contrast with the ineffectiveness of muscle stretch, sural nerve stimulation succeeded in recruiting 49/116 units, a proportion fairly typical of normal MG muscles. 4. The contractions of the first unit recruited in cutaneous reflexes tended to be slower and less forceful than those of the other unit in a pair. By these measures, recruitment obeyed the size principle. This recruitment order with respect to unit contractile properties was not significantly different (P > 0.05) between untreated and reinnervated muscles but was significantly (P < 0.005) different from random order in both groups. The same recruitment pattern was observed for pairs of motor units sampled from the muscle reinnervated after nerve crush, whether units were recruited by muscle stretch or sural nerve stimulation. 5. The usual tendency for motor units with slower conduction velocity (CV) to be recruited in sural nerve reflexes before those with faster CV was not strong in reinnervated muscles. After nerve section the proportion of units exhibiting the usual recruitment pattern was not significantly different (P > 0.05) from a random pattern for CV. 6. The central finding is that the normal recruitment patterns recover from nerve injury in a muscle that is reinnervated by its original nerve. By contrast, stretch reflexes do not recover well from nerve section, and this deficiency may contribute to motor disability.     

Stereotypic muscle-torque patterns are systematically adopted during acquisition of a multi-articular kicking task

Motor-control mechanisms used to learn multi-joint (kinematically indeterminate) movements, which involve the control of intersegmental dynamics, are poorly understood, because the few kinetic studies which examined them studied only a few trials performed early and late in learning. Therefore, we examined changes in movement kinematics and kinetics accompanying multi-joint movement acquisition to address the following questions: Once subjects can produce accurate movements, do motor patterns (i.e. net muscle torques) change with further learning? Are motor patterns learned using a systematic strategy? Following learning, are the same motor patterns consistently used for movement production? Subjects performed 16 blocks of 16 trials of a discrete weighted (mass = 1.674 kg) kicking movement, involving hip, knee, and ankle motion. They attempted to perform 400 ms spatially accurate movements. Kinematics were recorded for the hip, knee, ankle, and toe of the kicking leg, and inverse dynamics were used to obtain net-muscle-torque profiles. Subjects did not adopt the motor patterns initially used to produce accurate movements. With further learning, net muscle torques became less variable both within and between blocks; inter-joint dependency of muscle torques increased, as evidenced by decreased variability in the pair of muscle torques which directly affect a segment's motion (i.e. hip-knee and knee ankle muscle torques); and inter-joint relationships of muscle torques became more phase-locked, with hip and knee torques being produced simultaneously, as were knee and ankle torques. As there was a progression across blocks until the preferred motor patterns were adopted, the learned stereotypic motor patterns were systematically selected.     

Respiration and the generation of rhythmic outputs in insects

In insects gas exchange may be: 1) entirely passive, when metabolic rate is low; 2) enhanced automatically by muscle contractions that produce movements, e.g., wing movements in flight; or 3) produced by ventilatory movements, particularly of the abdomen. In terrestrial insects such as locusts and cockroaches ventilatory movements are governed by a dominant oscillator in the metathoracic or anterior abdominal ganglion. The dominant oscillator overrides local oscillators in the abdominal ganglia and thus sets the rhythm for the entire abdomen, and it also controls spiracle opening and closing in several thoracic and abdominal segments. This ventilatory control mechanism appears to be different from that generating metachronal rhythms such as occur in the ventilatory and locomotory movements of aquatic arthropods. There are now several examples of rhythms, both ventilatory and locomotory, that can be generated by the central nervous system in the absence of phasic sensory feedback, but the mechanism of rhythm production is not known. Studies of ganglionic output suggest that neuronal oscillators can produce a range of frequencies and that some oscillators may be employed in more than one function or behavior. The mechanisms by which central oscillators are coupled to the output motorneurons are also not known; large phase changes suggest that in some cases different coupling interneurons are active. Intracellular recordings from identified neurons have begun to clarify the important roles of interneurons in the production of motor patterns.     

Sensitivity to time change: The role of context and skill.

Three experiments used a 2-alterative, forced-choice procedure to examine the performance of skilled (musician) and unskilled (nonmusician) participants in detecting small time changes embedded within the test cycles of rhythmical patterns. Relational versus statistical properties of rhythms as well as rate and magnitude of to-be-detected time changes were varied in Experiments 1 and 2. Experiment 3 continued to vary structural properties of sequences (relational vs. statistical) and of experimental sessions. In general, listeners were better with relationally simple than with complex patterns in spite of the fact that the former were, on average, more variable; in addition, musicians were superior to nonmusicians only with simple sequences. In Experiment 3, more marked effects of relational structure within both pattens and sessions were evident. Results were interpreted in terms of an oscillator model of dynamic attending. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discharge pattern of neurons in the nucleus tractus solitarii (NTS): its cardiac rhythm is modulated by firing rate of the neurons

In the nucleus tractus solitarii (NTS) neurons discharge in relation to cardiac rhythm. This cardiac rhythm exhibits various patterns designated as CRDPs (cardiac rhythmic discharge patterns). The CRDPs are estimated by post-event-time histograms (PETH) triggered by the R-waves of the ECG. Modulations of CRDPs appear as changes in the number and height of peaks in the PETHs. The amount of basic activity, which is not related to the cardiac cycle, alters CRDP. PETHs constructed during various phases of respiration reveal modulations of CRDPs within the respiratory cycle. As our previous work indicated, the NTS neurons exhibit typical reticular rhythms. In this paper we also found that the basic activity of NTS neurons was often changed by other influences for which no comparable patterns could be observed in other simultaneously acquired signals. When we constructed PETHs according to the activity level of the NTS neurons, i.e., firing level per cardiac cycle, modulations of CRDPs which were even stronger than respiratory or reticular rhythmical modulations became clear. The modulations of CRDPs caused by different origins were found to be present in the same neuron interlaced in time. The possible role played by these modulations of CRDPs in the coordination of different functional systems in the organism is discussed.     

Resonance constraints on rhythmic movement.

The component frequencies of rhythmic patterns forming rational ratios, either simple (e.g., 1:2, 1:3) or complex (e.g., 2:3, 2:5), are known as mode locks or resonances. A general theory of resonances is provided by the circle map, the Farey series, and continued fractions. Predictions were evaluated in which rhythms (simple and poly) were established implicitly; the S neither intended them nor knew their ratios. In Exp 1, a prescribed unimanual frequency was performed as the primary task while hearing another frequency irrelevant to the task. In Exps 2 and 3, a hand-held pendulum was oscillated at its natural frequency, while the other hand performed the primary task of following a metronome. The frequency ratio at the outset of a trial often changed during the trial. Consistent with the general theory, shifts were toward unimodular ratios of the Farey tree, and Fibonacci ratios tended to shift more than non-Fibonacci ratios. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The importance of time as stimulus of conditioned reflex activity.

"The formation of conditioned reflexes to time plays an important part in the systemic activity of the cerebral cortex, in the development of definite periodicity in physiological functions, and in the establishment of rhythmical pattern reactions in the working activity of man. By virtue thereof the question of the cortical mechanisms involved in the process of formation of conditioned reflexes to time acquires considerable theoretical and practical importance." Studies, from Russian laboratories, employing a variety of experimental animals, and man, are cited. Experimental variables are systematically described as well as the many theoretical issues. 34 refs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Increases in vocalization and motor reflex thresholds are influenced by the site of morphine microinjection: Comparisons following administration into the periaqueductal gray, ventral medulla, and spinal subarachnoid space.

The relative influence of morphine microinjected into the periaqueductal gray, ventral medulla (nucleus raphe magnus or nucleus reticularis gigantocellularis), or spinal subarachnoid space on the thresholds of responses organized at spinal (spinal motor reflexes, SMRs), medullary (vocalizations elicited during shock, VDSs), and rhinencephalic-diencephalic (vocalization afterdischarges, VADs) levels of the neuraxis was assessed. Dose-dependent increases in response thresholds differed with the site of morphine injection. These results indicate that μ opiate receptor-linked systems in the mesencephalon, medulla, and spinal cord exert differential antinociceptive effects on pain behaviors organized at different levels of the neuraxis. A hypothesis is offered regarding the mechanisms through which morphine inhibits nociceptive transmission through various levels of the CNS. VADs are promoted as a model system for analyzing the affective-motivational dimension of the pain experience. (PsycINFO Database Record (c) 2010 APA, all rights reserved)