Functions of Auerbach's plexus.
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Afferent Pathways↗
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[The thalamus of the cat and the monkey. Anatomic, hodologic and functional data. Part I. The specific sensorial nuclei and the group of ventral nuclei].
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Afferent Pathways↗
[Cat stellate ganglion pathways].
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Afferent Pathways↗
Pupil in clinical diagnosis. Light reflex anatomy and the afferent pupil defect.
The neuroanatomy for the light reflex has been reviewed. The importance of the semidecussation of visual pathways in the afferent portion of the system has been emphasized. The anatomy of the near synkinesis and its relation to the anatomy of the light reflex have been reviewed. The various abnormalities of sensory pupil function have been outlined. Particular stress has been placed on the value of the afferent pupil defect in the diagnosis of sensory lesions affecting the eye because of retinal or optic nerve disease. In addition, the value of the consensual pupil in the diagnosis of afferent defects has received special comment.
Accommodation, Ocular↗
c-fos expression in the rat hypothalamic paraventricular nucleus induced by LiCl: descending projections to the dorsal vagal motor nucleus.
Anorexia inducing lithium chloride is believed to involve descending projections from hypothalamus to preganglionic autonomic output neurons. A multiple-labelling technique has presently been used to analyze the anatomical projections of lithium chloride sensitive neurons in the hypothalamus. Immunolabelling of c-fos was performed to stain neurons activated after LiCl administration, while neurons projecting toward vagal parasympathetic preganglionic levels were identified by injection of diamidino yellow in the dorsal motor nucleus of the vagus. Perikarya of descending neurons were mainly observed in the ventral and lateral areas of the paraventricular hypothalamic nucleus. In contrast, lithium chloride activated neurons were observed mainly in the magnocellular division of the paraventricular nucleus and supraoptic nucleus. Double-labelled neurons were not observed. These data provide evidence that lithium chloride sensitive neurons in the paraventricular nucleus are clearly different from those descending toward preganglionic vagal outflow neurons.
Animals↗
Beyond Ashworth. Electrophysiologic quantification of spasticity.
Spasticity is a hallmark of upper motor neuron lesion, which is easily identified but is difficult to quantify and treat. The Ashworth scale lacks reliability. Available biomechanical and electrophysiologic studies offer a more reliable measure of spastic hypertonia but have limited clinical utility. A uniformly acceptable, reliable, and practical measure of spasticity continues to elude the clinician. This chapter reviews the basic neuroanatomy and physiology of the stretch reflex and the pathophysiology of the spasticity. Current biomechanical and electrophysiological techniques are used to quantify spasticity.
Afferent Pathways↗
Trigeminal integration of vestibular and forelimb nerve inputs.
Experiments were carried out on anaesthetized guinea pigs to evaluate whether vestibular and somatosensory informations converge upon the same trigeminal motoneurones and, if so, how they interact in the modulation of their activity. It was found that excitatory responses occurred in these motoneurones when an appropriate electrical stimulation was applied to the common radial nerve. The same was true if the electrical stimulus was applied to the vestibular ampullae. In another set of experiments the stimulation was applied both to the vestibular ampullae and to the common radial nerve at various time-intervals. The amplitude of the motoneuronal responses to common radial nerve stimulation was reduced when preceded by a vestibular stimulation. The same was true when the sequence of stimulations was reversed: in this case there was a decrease in amplitude of the testing response to vestibular stimulation. The degree of these reductions depended upon the time-interval elapsed between the afferent stimulations. The maximal degree of depression was observed at 4-6 ms time-interval for conditioning vestibular stimulation and at 10-12 ms time-interval for conditioning radial nerve stimulation. It appears, therefore, that somatosensory and vestibular signals may modulate the activity of trigeminal motor units innervating masticatory muscles, suggesting that extratrigeminal afferents may control the contraction of these muscles.
Afferent Pathways↗
Coordinated host defense through an integration of the neural, immune and haemopoietic systems.
Interactions between the neural and immune systems exist through humoral factors operating via the hypothalamic-pituitary-adrenal axis and cytokines acting over a relatively long distance. Anatomical evidence also suggests direct, hard-wired pathways of interaction and control through innervation of lymphoid organs and peripheral sites involved in host defense, including the thymus, spleen, lymph nodes, and skin. Recent evidence has demonstrated: 1) neural control of the bone marrow haemopoietic system, 2) interactions between peripheral nerve endings in the skin and epidermal Langerhans cells, and 3) peripheralization of leukocytes in the initial stages of stress. This leads us to propose that the nervous system is involved in host monitoring and coordination of host defense systems. If the brain is to have appropriate control of host defense mechanisms it must have: (a) afferent inputs monitoring host defense status, (b) efferent control pathways that modulate primary reactions to infection and damage, (c) efferent activation pathways to the myeloid defense system while the specific, lymphoid immune system is activated, and (d) inhibition of the proliferative lymphocytic response if the infection has been dealt with. We are investigating whether such a model, which allows for control and coordination of both the initial myeloid defense system and of the acquired immune response, is observed in mammals.
Animals↗
[Can the efferent auditory system be explored via early evoked potentials? Preliminary results in normal hearing subjects and people with tinnitus].
The use of masking in brainstem auditory evoked potential technic remains one of the important issue regarding the evaluation of different auditory control systems. Brainstem auditory evoked response wave form latencies and amplitudes have been studied on 14 normal hearing subjects. On one hand the contralateral masking which theoretically stimulates the medial contralateral efferent bundle did not modify the responses. On the other hand, the ipsilateral masking stimulating the lateral bundle reduced the amplitude of wave I and lengthened the latency of interwave I to V. The same protocol has been applied to 21 tinnitus patients. In these subjects before masking, the waves amplitude was lower and inter wave I-V latency was lengthened. The ipsilateral did not modify the responses as in the normal population. Comparing brainstem responses obtained in masking and no masking condition offers the possibility of evaluating the lateral efferent system function but we can conclude that the contralateral masking is of no use studying the medial system and that dysfunctions of the lateral efferent system could be one mechanism responsible for tinnitus.
Adult↗
Mapping of the motor pathways in rats: c-fos induction by intracortical microstimulation of the motor cortex correlated with efferent connectivity of the site of cortical stimulation.
The general goal of the present study was to investigate structural components of a neural system anatomically as well as functionally. The rat motor system, which is reasonably well understood, was selected and a new procedure was developed to combine a functional marker with axonal tracing methods (in the same animal). This was achieved by mapping c-fos induction immunocytochemically as a result of intracortical microstimulation in the distal forelimb area of the motor cortex. The anterograde tracers Phaseolus vulgaris-leucoagglutinin or biocytin were deposited at the site of intracortical microstimulation, the former three weeks and the latter two to three days before stimulation. Neuronal nuclei, labeled for the expressed c-fos protein, were present and mapped in the following structures: motor cortex; basal ganglia (caudate-putamen, globus pallidus); thalamus (reticular, ventromedial and posterior nuclei); subthalamic nucleus; substantia nigra; tectum; red nucleus; pontine nuclei; inferior olive; external cuneate nucleus; cerebellar cortex; deep cerebellar nuclei. Labeling was often bilateral but generally more substantial ipsilaterally, except in the cerebellum where it was mainly contralateral. Axonal labeling, including terminal branches and boutons, was also found in most of the above structures with the exception of the globus pallidus, deep cerebellar nuclei, cerebellar cortex and external cuneate nucleus. These expected exceptions demonstrate that activity changes in these latter structures, as revealed by c-fos labeled neurons, were induced over more than one synapse. This combined procedure might, therefore, be useful in deciding whether two structures in a given system are linked directly (monosynaptically) or indirectly (polysynaptically) to each other. In contrast to the 2-deoxyglucose technique, functional mapping by means of c-fos induction provides cellular resolution, making it possible to establish fine details of axonal contacts with target neurons: boutons in close apposition to c-fos labeled neurons were clearly observed here, for instance in the cerebral cortex, caudate-putamen, thalamus, subthalamic nucleus and pontine nuclei. Surprisingly, the ventrolateral and ventrobasalis nuclei of the thalamus contained numerous and dense axon terminals labeled with Phaseolus vulgaris-leucoagglutinin or biocytin, but the contacted neurons in the ventrolateral and ventrobasalis nuclei were not marked with c-fos. However, with respect to directly connected structures, there was, in general, a good correlation between structures with axonal labeling and those with c-fos labeled neurons.
Animals↗
Efferent subcortical projections of the laryngeal motorcortex in the rhesus monkey.
In order to better understand the descending voluntary vocal control pathway, the efferent subcortical projections of the laryngeal motorcortex were studied in the rhesus monkey (Macaca mulatta). For this purpose, the left motorcortex was exposed in three animals under narcosis. By electrical brain stimulation, sites were identified yielding vocal fold adduction. Effective sites were injected with the anterograde tracer biotin dextran amine. Subcortical projections could be traced within the forebrain to the putamen, caudate nucleus, claustrum, zona incerta, field H of Forel and a number of thalamic nuclei, with the heaviest projections to the nuclei ventralis lateralis, ventralis posteromedialis, including its parvocellular part, medialis dorsalis, centralis medialis, centrum medianum and reuniens. In the midbrain, labeling was found in the deep mesencephalic nucleus. In the lower brainstem, fibers terminated in the pontine and medullary reticular formation, locus coeruleus, nucleus subcoeruleus, medial parabrachial nucleus, nucleus of the spinal trigeminal tract, solitary tract nucleus and facial nucleus. No projections were found to the nucl. ambiguus. The fact that monkeys, in contrast to humans, lack a direct connection of the motorcortex with the laryngeal motoneurons suggests that this connection has evolved in the last few million years and might represent one of the factors that made speech evolution possible.
Afferent Pathways↗
Otoacoustic emission and auditory efferent function testing in patients with sensori-neural hearing loss.
OBJECTIVE: To examine the role of otoacoustic emissions and auditory efferent system function in evaluating auditory functional status in both normal and diseased conditions. METHODS: Spontaneous and transient evoked otoacoustic emissions and efferent function in terms of contralateral white noise induced transient evoked otoacoustic emission suppressions were tested and cross compared in 32 normal ears, 24 ears with cochlear hearing loss and 16 ears with retrocochlear hearing loss. RESULTS: Transient evoked otoacoustic emission amplitude and contralateral suppression, spontaneous otoacoustic emission incidence, peaks and frequency range were significantly reduced in cochlear hearing loss while in retrocochlear hearing loss transient evoked otoacoustic emission and spontaneous otoacoustic emission levels were significantly higher than in cochlear hearing loss group and showed no suppression. CONCLUSIONS: Contralateral acoustic stimulation induced transient evoked otoacoustic emission suppression as an index of efferent function is clinically feasible. Combined otoacoustic emission and efferent tests are of great significance in evaluating cochlea status and auditory central mechanisms. Auditory efferent function is weakened in cochlear lesions and severely damaged in retrocochlear lesions.
Adolescent↗
Role of the efferent and afferent vagus nerve in the development of ventromedial hypothalamic (VMH) obesity.
Hyperactivity of the vagus nerve and hypoactivity of the sympathetic nerves after VMH lesions both cooperatively contribute to the development of VMH obesity, mainly through hyperinsulinemia. Recently it has turned out that we should discriminate the role of the efferent vagus from that of the afferent vagus in the pancreatic hormone secretion. The hepatic branch is the main pathway of afferent fibers in the vagus, while the celiac (pancreatic) branch is the main pathway of efferent fibers. We investigated the role of the afferent and efferent vagus on the development of VMH obesity using the sectioning of the hepatic and celiac branch. Celiac vagotomy decreased insulin secretion and food intake, while hepatic vagotomy did not change them. The results suggested that the efferent vagus plays the main role in the development of VMH obesity, while the role of afferent vagus seems less apparent.
Afferent Pathways↗
Do efferent fibres to hair cells intervene in acoustic stimulus peripheral coding?
The functional roles suggested for Olivo-Cochlear Bundle (OCB) fibres innervating auditory receptors never received a fully convincing demonstration. Assuming that efferent fibres effects, at the level of hair cells, are inhibitory with regard to single auditory nerve fibre activity, a mathematical model of the peripheral auditory system is proposed in which the presence of the descending pathway is taken into account. Computer simulation of the model accounts for most of the salient features of the patterns of activity of single cochlear nerve fibres. In the light of the model predictions, the influence of OCB fibres on peripheral receptors is assumed to act in the direction of improving the signal-to-noise ratio, as a first step of information processing.
Acoustic Stimulation↗
Hypothalamic control of brown adipose tissue in Zucker lean and obese rats. Effect of electrical stimulation of the ventromedial nucleus and other hypothalamic centres.
Electrophysiological stimulation of the hypothalamic ventromedial nucleus (VMN) resulted in an increase in interscapular brown adipose tissue (BAT) temperature in both lean and obese (fa/fa) rats. Graded stimulations resulted in progressively larger temperature increases in both lean and obese (fa/fa) groups. Both intraperitoneal injection of propranolol and surgical denervation (but not sham denervation) abolished the increase in BAT temperature following VMN stimulation, in both lean and obese (fa/fa) groups. Electrical stimulation of the supraoptic region, and certain anterior hypothalamic regions also resulted in increases in BAT temperature of lean and obese (fa/fa) rats, but stimulation of the dorsomedial nucleus and regions of the lateral hypothalamus did not affect BAT temperature. All hypothalamic regions capable of activating BAT gave a similar maximum rise in temperature for a given stimulus in lean and obese (fa/fa) rats. These results suggest that the efferent sympathetic pathway from the VMN and other hypothalamic regions of BAT is normal in the obese (fa/fa) rat.
Adipose Tissue, Brown↗
Effects of chronic left vagal stimulation on visceral vagal function in man.
We examined the effects of chronic left vagal electrostimulation on afferent and efferent gastrointestinal vagal function in eight patients. Afferent function was assessed using cortical evoked responses to electrical stimulation of the esophagus and to direct vagal stimulation using the implanted left vagal electrode. Efferent gastrointestinal vagal function was measured by examining the basal, maximal, and sham fed stimulated gastric acid output prior to and with chronic left vagal electrostimulation. Esophageal electrostimulation produced a cortical evoked response consisting of three negative and three positive peaks within 400 msec after stimulation. Prior to vagal electrostimulation the mean conduction velocity of the afferent signal was measured at 8.72 +/- 3.39 m/sec, compatible with A-delta fibers involvement. Basal, maximal, and sham fed acid output were 1.11, 21.87, and 9.37 mmol/hour, respectively. The evoked response to esophageal electrical stimulation was not changed with chronic left vagal electrostimulation. Direct vagal stimulation also produced evoked potentials that were comparable to those obtained with esophageal stimulation. The mean conduction velocity was 6.26 +/- 2.72 m/sec (NS) so that there was no evidence of loss of myelinated fibers with chronic stimulation. No differences were detected in basal (1.29 mmol/h), maximal (21.64 mmol/h), or sham fed stimulated (8.03 mmol/h) acid output, showing that vagal electrostimulation has no effect on either total or vagally mediated acid output, an efferent vagal function. In conclusion, chronic left vagal electrostimulation has no significant adverse effect on gastrointestinal vagal function.
Adult↗
Ascending lateral line pathways to the midbrain of the clearnose skate, Raja eglanteria.
Efferent projections of the electroreceptive dorsal and the mechanoreceptive intermediate octavolateralis nuclei were revealed, in the brain of the clearnose skate Raja eglanteria, by means of silver degeneration and autoradiographic methods. Efferents from each nucleus give rise to ipsilateral and contralateral lemnisci and commissural components. Commissural fibers terminate within their respective nuclei of the opposite side. The lemnisci from each nucleus parallel each other as they course from medullary to mesencephalic levels; those from the dorsal nucleus assume a lateral position and terminate within the lateral part of the nucleus of the lateral line lemniscus and the lateral nucleus of the midbrain; those within the medial part of the lateral line lemniscal nucleus and the dorsomedial mesencephalic nucleus. A substantial number of fibers of each class course through the mesencephalic nuclei and terminate bilaterally within the central tectal zone. The segregation of electroreceptive and mechanoreceptive information is maintained from medullary to mesencephalic levels although there probably is convergence within the central tectal zone and the magnocellular nucleus, the only octaval center to receive terminals from secondary lateral line fibers.
Animals↗
Early estrogen treatment of female zebra finches masculinizes the brain pathway for learned vocalizations.
Telencephalic nucleus HVC and its two efferent targets, RA and X, play essential roles in the production of complex, learned vocalizations in the male zebra finch. Normal females do not produce these learned vocalizations; HVC, RA, and X are small in volume, and HVC and RA are not synaptically connected. We have shown that estrogen treatment during development causes females to learn and produce male-like vocalizations. This article describes the neural masculinization of these E2 females, replicating and extending the work of others. Female zebra finches were treated with 17 beta-estradiol (E2) at hatching, at 14-22 days of age, or as adults. In adulthood, the volumes of nucleus RA and area X were measured and the efferent projections of nucleus HVC examined using the anterograde tracer PHA-L. Early, sustained E2 treatment caused the greatest increase in the volume of RA and X, the innervation of RA and X by HVC axons, and the masculinization of auditory responses of cells in RA. Treatments that lasted for a shorter period or started later in development resulted in different patterns of partial brain masculinization. E2 treatment in adulthood had no effect on the volume of RA or X or their innervation by HVC. Bilateral lesions of the tracheosyringeal nerves or of HVC had the same effects on the male-typical vocalizations produced by E2 females as they do on the vocalizations produced by males. These results demonstrate that the neural masculinization of telencephalic nuclei induced by E2 treatment sets up a functional circuit in females similar to one in males that enables the learning and production of complex vocalizations.
Age Factors↗