Role Of Sensory Input Research Articles

Role of Sensory Input and Muscle Strength in Maintenance of Balance, Gait, and Posture in Parkinson???s Disease

The purpose of this study was to simultaneously evaluate multiple components of disequilibrium in patients with idiopathic Parkinson's disease (PD) in ON and OFF states and healthy age- and sex-matched controls on tests of balance, gait, and dynamometry. Thirty subjects with Parkinson's disease and 30 controls were matched for age and sex. Isokinetic and balance laboratories of a clinical research center were used for assessment. Performance results for static and dynamic balance by dynamic posturography for sensory organization tests (SOT), limits of stability, clinical gait assessment, and dynamometric assessment for the trunk, hip, and ankle at different speeds for concentric muscle strength were obtained. Tests were done both in ON and OFF state in Parkinson's disease patients and results compared. Between OFF state and controls, a significant difference was observed for SOT-2 (proprioception, P < 0.005), SOT-6 (conflicting vision, P < 0.001), and SOT-4 (eyes open with sway support, P < 0.038), and there was less use of ankle strategy in SOT-3 (sway vision, P < 0.04). No significant difference was observed for vestibular function (SOT-5). Significant difference was also observed (P < 0.001) for all variables in limits of stability except for reaction time and for muscle strength of trunk, hip, and ankle (P < 0.001) between OFF state and controls. After antiparkinsonian medications, significant improvement was observed for gait velocity (P < 0.002), muscle strength (P < 0.001), and strategy score in SOT-3 between OFF and ON states. A positive correlation was observed between muscle strength (ankle, hip, and trunk) and gait velocity (ON state r = 0.37, OFF state r = 0.56) and movement velocity (ON state r = 0.39). A positive correlation was also seen between ankle strength and gait velocity in both ON (r = 0.393) and OFF states (r = 0.397) and between ankle strength and ankle strategy in all SOTs except SOT-3 in the OFF state. The quantitative reduction of muscle strength in the spine, hip, and ankle, along with impaired proprioception, visual sense, and smaller base of support, were the main causes for postural instability in Parkinson's disease patients. A correlation was seen between muscle strength, static and dynamic balance, and gait in both ON and OFF states. In contrast to the previous studies, the present study showed that medications improved the muscle strength, gait speed, and use of ankle strategy but did not worsen proprioceptive sense.

Role of sensory input from the lungs in control of muscle sympathetic nerve activity during and after apnea in humans.

We reasoned that, if the lung inflation reflex contributes importantly to apnea-induced sympathetic activation, such activation would be attenuated in bilateral lung transplant recipients (LTX). We measured muscle sympathetic nerve activity (MSNA; intraneural electrodes), heart rate, mean arterial pressure, tidal volume, end-tidal Pco(2), and arterial oxygen saturation in seven LTX and seven healthy control subjects (Con) before, during, and after 20-s end-expiratory breath holds. Our evidence for denervation in LTX was 1) greatly attenuated respiratory sinus arrhythmia and 2) absence of cough reflex below the level of the carina. During apnea, the temporal pattern and the peak increase in MSNA were virtually identical in LTX and Con (347 +/- 99 and 359 +/- 46% of baseline, respectively; P > 0.05). In contrast, the amount of MSNA present in the first 5 s after resumption of breathing was greater in LTX vs. Con (101 +/- 4 vs. 38 +/- 7% of baseline, respectively; P < 0.05). There were no between-group differences in apnea-induced hypoxemia or hypercapnia, hemodynamic, or ventilatory responses. Thus cessation of the rhythmic sympathoinhibitory feedback that normally accompanies eupneic breathing does not contribute importantly to sympathetic excitation during apnea. In contrast, vagal afferent input elicited by hyperventilation-induced lung stretch plays an important role in the profound, rapid sympathetic inhibition that occurs after resumption of breathing after apnea.

&lt;b&gt;Phantom limb pain and the phenomenology of body image &lt;/b&gt;

During the last decade, the neuromatrix theory proposed by Melzack has attracted considerable attention as a basis for exploring the mechanism underlying phantom limb pain. In the neuromatrix theory, emphasis is placed on the role of sensory input as well as motor output in synthesizing the neurosignature that gives rise to the quality of the self, the feeling that all parts of the body are uniquely one's own. This view resembles that of Husserlian phenomenology, which analyzes the formation of body image through changes in sensory experience induced by body movement, termed Kinesthese. The present paper analyzes various clinical findings in patients with phantom limb pain, who were treated by thalamic relay nucleus stimulation, from a phenomenological standpoint, and discusses how the results of such an analysis are reconciled with the neuromatrix theory. While attention has been paid mainly to disturbances of sensory input in investigating the mechanism of phantom limb pain, more research on the role of disturbances of motor output may be needed in order to clarify the exact picture of the pathophysiology of phantom limb pain and to establish an efficient therapeutic approach to this form of pain.

Sensory control of locomotion: reflexes versus higher-level control.

In the absence of sensory input, the central nervous system can generate a rhythmical pattern of coordinated activation of limb muscles. Contracting muscles have spring-like properties. If synergistic muscles are co-activated in the right way, sustained locomotion can occur. What is the role of sensory input in this scheme? In this chapter we first discuss the implications of positive force feedback control in hindlimb extensor reflexes in the cat. We then raise the question of whether the sensory-evoked responses, which are modest in size and quite delayed in the stance phase, contribute to any significant extent. A locomotor model is used to show that when centrally generated activation levels are low, stretch reflexes can be crucial. However, when these levels are higher, stretch reflexes have a less dramatic role. The more important role for sensory input is probably in mediating higher level control decisions.

The role of sensory input in motor neuron sprouting control

Primary sensory neurons project to motor neurons directly or through interneurons and affect their activity. In our previous paper we showed that intramuscular sprouting can be affected by changing the sensory synaptic input to motor neurons. In this work, motor axon sprouting within a peripheral nerve (extramuscular sprouting) was induced by nerve injury at such a distance from muscle so as not to allow nerve-muscle trophic interactions. Two different procedures were carried out: (1) sciatic nerve crush and (2) sciatic nerve crush with homosegmental ipsilateral L3-L5 dorsal rhizotomy. The number of regenerating motor axons innervating extensor digitorum longus muscle was determined by in vivo muscle tension recordings and an index of their individual conduction rate was obtained by in vitro intracellular recordings of excitatory postsynaptic end-plate potentials in muscle fibers. The main findings were: (1) there are more regenerated axons distally from the lesion than parent axons proximally to the lesion (sprouting at the lesion); (2) sprouting at the lesion was negatively affected by homosegmental ipsilateral dorsal rhizotomy; (3) the number of motor axons innervating extensor digitorum longus muscle extrafusal fibers counted proximally to the lesion increased following nerve injury and regeneration but this did not occur when sensory input was lost. A transient innervation of extrafusal fibers by n motor neurons may explain the increase of motor axons counted proximally to the lesion.

Restless Legs Syndrome In Peripheral Neuropathy

Restless legs syndrome (RLS) is increasingly recognized as a manifestation of various forms of peripheral neuropathy, and in particular in association with amyloidosis, uremia, diabetes, cryoglobulinemia, and Charcot‐Marie‐Tooth disease type 2. A previous study demonstrated a 5% prevalence of RLS in unselected neuropathies, but did not elucidate factors influencing the occurrence, or not, of RLS in peripheral neuropathy. We studied a series of unselected neuropathic patients to assess the prevalence of RLS, and to define the features of peripheral neuropathy associated with RLS. In a population of 70 consecutive patients with various forms of peripheral neuropathy (polyneuropathy in 65 cases, multiple mononeuropathy in 5 cases) we found RLS in 20 cases (28.6%). In particular, RLS was more often associated with cryoglubolinemic neuropathy (5/13), diabetic neuropathy (4/12), Charcot‐Marie‐Tooth disease (4/18), and chronic idiopathic axonal polyneuropathy (2/6). RLS was usually associated with a neuropathy of axonal type, and the onset of RLS was 0–10 (median 1) years after the onset of neuropathy; in 9 cases, RLS was an initial manifestation of neuropathy. Patients with pure sensory or mainly sensory neuropathy had RLS more often than patients with other patterns of neuropathy (13/37 vs. 7/33). Severity of neuropathy, as judged by Rankin score, did not differ in patients with or without RLS (13/20 with Rankin grade 2 or more, vs. 36/50). Prevalence of RLS in our population of neuropathic patients was higher than previously reported. Thus RLS may be viewed as a quite common manifestation of peripheral neuropathy in general, although more common in some forms, and it represents a treatable neuropathic symptom. Mechanisms of RLS are elusive, however a role of sensory inputs is supported by its greater incidence in association with sensory neuropathies.

Visual projections induced into the auditory pathway of ferrets: II. Corticocortical connections of primary auditory cortex

Although the development of corticocortical projections has been well studied, less is known about the role of sensory inputs in the specification of these connections. As part of an ongoing series of studies in our laboratory, we have examined the role of thalamic input modality in the development of corticocortical connections. These studies involve making unilateral lesions and inducing retinal inputs into the auditory thalamus (MGN) during early development in ferrets, thereby conferring visual responsiveness on primary auditory cortex (AI). In this way we can examine the role of input identity in cortical specification in general, and connectivity patterns specifically. A previous paper (Pallas et al. [1990] J. Comp. Neurol. 298:50-68) described the pattern of thalamocortical and corticothalamic connections of auditory cortex in normal and lesioned animals. This study compares the pattern of auditory corticocortical connections in normal and lesioned animals. We injected neuroanatomical tracers into AI and mapped out the distribution of retrogradely labelled cells in the cortex. We report that the cortical inputs to ferret AI resembled those in cats, and that the pattern of ipsi- and contralateral corticocortical connections of ferret AI with visual input was similar to the normal pattern. Auditory cortex with visual input did not make ectopic connections with visual cortex, but maintained its connections with other auditory cortical areas. These results suggest that the overall corticocortical connections of an area are not influenced by the modality or activity pattern of its inputs. In particular, altering the input activity to a cortical area does not seem to promote the formation of entirely new connections, although small changes in the strength of existing connections are possible (Sur et al. [1990] Trends Neurosci. 13:227-233).

The role of sensory input in maintaining output from the locust oviposition digging central pattern generator

A quantitative EMG analysis is presented of the effects of deafferentation on the motor program for oviposition digging in the locust Locusta migratoria. We examined the activity of two groups of antagonistic muscles, the opener and closer muscles of the ventral ovipositor valves, in terms of the cycle frequency, burst duration, and relative burst onset times. There were no significant differences between the pattern frequency produced in intact, semi-intact, or deafferented animals within 10 min of the onset of the pattern. Over time, however, the pattern in deafferented animals showed a significant decrease in frequency, which it did not do in intact or semi-intact animals. Seven out of 10 deafferented preparations ceased producing the digging rhythm within 35 min of onset, but none of the semi-intact preparations did so. Mechanosensory hairs cover the ovipositor valves, and are in a position to supply sensory input to the digging pattern generator during the natural behaviour. When nerves carrying sensory axons from these hairs were electrically-stimulated tonically, the motor pattern was restored in deafferented animals. The effects of the stimulation outlasted the stimulation itself for several minutes, and could be repeated several times. We suggest that tonic input is necessary for the maintenance of the digging rhythm, possibly by maintaining levels of some modulatory substance(s) within the CNS.

The role of the sensory input and its significance in the masticatory system

The role of the sensory input and its significance in the masticatory system

Abolition of CA1 population spike by sensory stimulation.

The effect of sensory stimulation, such as stroking of the animals' fur, on activation of the hippocampal CA1 field was studied in paralyzed and locally anaesthetized rats. CA1 population responses evoked either monosynaptically (ipsilateral CA3 stimulation) or trisynaptically (perforant pathway stimulation) decreased markedly when sensory stimulation was applied, and CA1 population spikes were absent during most periods of sensory stimulation. These results demonstrate the strong modulatory role of sensory inputs on hippocampal circuits.

The role of sensory inputs in insect flight motor pattern generation

Studies on intact flying locusts are revealing the important part played by phasic sensory inputs in regulating the flight motor output in insects and require a radical revision of the concept of the flight pattern generator.

Effects of Acoustico-Lateralis denervation in a facultative schooling fish: a nearest-neighbor matrix analysis

Spacing responses in schools of golden shiner fish were measured before and after surgical section of the posterior lateral line (acoustico-lateralis) nerves. Test fish swam closer to their five nearest schoolmates after surgery and maintained less parallel orientation to their nearest neighbors. These findings indicate a significant role of lateral line input in the spacing responses of these facultative-schooling freshwater fish. Fish maintained nonrandom patterns of spacing toward their five nearest schoolmates before surgery, distinguished by closer distances, more parallel orientation, and greater avoidance of positions behind schoolmates than expected by chance. Analysis revealed that both school structure and behavioral changes after lateral line surgery resemble what is known of obligate-schooling marine fish species. Results are discussed in the context of lateral line function in fish spacing responses and the role of sensory input in fish schooling.

Effects of bilateral limb-bud extirpation on motility and prehatching behavior in chicks.

AbstractThe role of sensory input in the performance of overt motility by the chick embryo has been a matter of controversy. Although it has been proven that embryonic motility is generated in the motor system of the spinal cord and does not require sensory input up to 15 days, it has been suggested that self‐stimulation and related “experiences” during embryonic development are instrumental in the structuration or facilitation of normal embryonic and post‐hatching motor patterns. Using microsurgical techniques, hind‐limb buds were extirpated bilaterally in chick embryos at three days of incubation in order to eliminate a major source of self‐stimulation to the head by the legs. The total motility of legless chicks in not significantly different from that of the control embryos between 11 and 17 days. Part of the pre‐hatching and hatching behavior repertory is also performed normally by the legless embryos. However, they do not hatch, probably because the bracing of the tarsal joints against the shell is necessary for the rotatory movements during hatching. Feeding, drinking and righting after hatching are normal.