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Results for “sensorimotor function”

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PubMed1984

Spinal reflex alterations as a function of intensity and frequency of vibration applied to the feet of seated subjects.

Sensorimotor system performance is known to be altered by vibration applied locally to tendons and muscles or to the whole body. The present study is an attempt to determine the influence of vibration amplitude, acceleration, and frequency on the excitability of the motoneurons as evaluated by the amplitude of electrically induced spinal reflex response in man. The results show that a vibration applied to the legs of a seated subject (S) decreased the reflex response. The effect is directly related to the vibration intensity. The reflex amplitude is minimal in the 10-30 Hz range. At constant acceleration, the depressive effect decreased beyond 20-30 Hz while, at constant displacement amplitude, the reflex inhibition was almost constant throughout the frequency range of 20-60 Hz. These observations suggest that the diminution of the reflex response is mainly related to the amplitude of the vibration, regardless of the frequency. The results are interpreted in light of current knowledge of the effect of locally applied vibration on muscle tendons. The marked inhibition observed in the 10-30 Hz range, even with moderate intensity, suggests that particular attention should be devoted to avoid vibration in that frequency range in vehicles in order to prevent alteration of the performance of sensorimotor systems.

Adolescent↗

PubMedDate not supplied

Structure of the human sensorimotor system. I: Morphology and cytoarchitecture of the central sulcus.

We have studied the morphology of the central sulcus and the cytoarchitecture of the primary sensorimotor cortex in 20 human brains obtained at autopsy. Although the surface appearance of the central sulcus varies greatly from brain to brain (and between hemispheres of individual brains), its deep structure is remarkably consistent. The fundus of the central sulcus is divided into medial and lateral limbs by a complex junction midway between the sagittal and Sylvian fissures. Based on functional imaging studies, this junction appears to be a structural hallmark of the sensorimotor representation of the distal upper extremity. We also identified and measured area 4 (primary motor cortex) and area 3 (primary somatic sensory cortex) in Nissl-stained sections cut orthogonal to the course of the central sulcus. Although the positions of the cytoarchitectonic boundaries in the paracentral lobule showed considerable interindividual variation, the locations of the borders of areas 4 and 3 along the course of the sulcus were similar among the 40 hemispheres examined. In addition to describing more thoroughly this portion of the human cerebral cortex, these observations provide a basis for evaluating lateral symmetry of the human primary sensorimotor cortex.

Cerebral Cortex↗

PubMed2004

Motor and cognitive function evaluation following experimental traumatic brain injury.

Traumatic brain injury (TBI) in humans may cause extensive sensorimotor and cognitive dysfunction. As a result, many TBI researchers are beginning to assess behavioral correlates of histologically determined damage in animal models. Although this is an important step in TBI research, there is a need for standardization between laboratories. The ability to reliably test treatments across laboratories and multiple injury models will close the gap between treatment success in the lab and success in the clinic. The goal of this review is to describe and evaluate the tests employed to assess functional outcome after TBI and to overview aspects of cognitive, sensory, and motor function that may be suitable targets for therapeutic intervention.

Animals↗

PubMed1991

Peripheral pain fiber function is relatively insensitive to the neurotoxic actions of acrylamide in the rat.

Acrylamide causes degeneration of sensory nerve axons in a range of experimental animals and in humans. Evidence of selective vulnerability of large diameter fibers has been derived largely from histological and electrophysiological measurements. We have examined the effect of repeated doses of acrylamide on the function of small diameter peripheral pain fibers in rats by measuring the intensity of neurogenic edema initiated by chemosensitive nerve endings and assessing the sensitivity of the hind paws to a noxious stimulus. These effects have been compared to the impaired sensorimotor performance (landing foot spread) resulting from acrylamide treatment and the change in functional integrity of the pain fibers following surgical lesioning of the sciatic nerves. Our results show that the selective vulnerability of large over small diameter sensory fibers previously reported in the literature is reflected in the differential impairment of proprioceptive and pain-related functions in the rat.

Acrylamide↗

PubMedDate not supplied

[Comparative evaluation of visual function computer examining methods for early diagnosis of glaucoma].

Computer methods for examining the visual functions are compared: computer-aided campymetry from the time of the sensorimotor reaction, computer-aided color campymetry, visocontrastometry, and threshold static perimetry (program 24-2) with Humphrey's visual field analyzer. These methods were used in examinations of 65 patients (105 eyes) with primary open-angle glaucoma at various stages of the disease. A complex of sufficiently sensitive psychophysical methods for examination of the visual functions has been defined, including computer-aided campymetry and visocontrastometry, which may be used for early diagnosis of glaucoma.

Aged↗

PubMed2003

Examination of sensorimotor performance following middle cerebral artery occlusion in rats.

Middle cerebral artery occlusion (MCAO) in rats is the most commonly used stroke model. Besides the infarct size, assessment of sensorimotor performance has become increasingly important in neuroprotective drug research. However, contradictions exist about procedures for testing functional outcome following MCAO. The aim of the present study was to evaluate a relatively simple set of neurological tests based on the most commonly used scoring systems, and to describe the functional recovery and correlation with the infarct size in rats sacrificed 2 or 14 days after permanent or transient MCAO. The smaller infarct size of rats with transient occlusion was reflected in the neurological scores only during the first 6h. By day 14, no recovery occurred in postural signs, lateral resistance and spontaneous activity, other signs showed different degrees of recovery. Correlation with the infarct size was found only on certain days in gait disturbance, placing reactions, daily body weight and spontaneous activity. According to our observations, the most commonly used sensorimotor tests provide a useful initial screening of functional deficits, but these tests most probably measure deficits caused by infarction of the core area. It is suggested that these tests should be completed by more refined tests when testing a neuroprotective drug which reduces the infarct size in penumbral areas.

Animals↗

PubMedDate not supplied

Pharmacological testing of intracortical interneuronal connections.

The present study comprises an attempt to investigate the influence of acetylcholine on the functional connections of the cortical cells and their frequency characteristics. The multineuronal activity was recorded in the sensorimotor cortex of immobilized and freely moving rats, and was subsequently analyzed using the method of cross-correlational analysis. In the first series of experiments, the influence of the neuromediator, acetylcholine (ACh), and calcium chelation, ethyleneglycol tetraacetate (EGTA), on the functional characteristics of adjacent neurons during the iontophoretic application of these substances to cells of the sensorimotor cortex of unanesthetized immobilized rats was investigated. In this case, the iontophoretic application of ACh led to a change in the frequency characteristics of individual neurons, and in the majority of cases did not influence the character of the interneuronal interactions. The application of EGTA led to a decrease in the average frequency of impulse activity for the majority of the neurons, as well as to the disappearance, independent of the running frequency, of excitatory connections in the cross-correlograms, with their subsequent recovery following the termination of exposure to the EGTA. In the second series of experiments, carried out in freely moving rats with a chronically implanted recording electrode, the systemic administration of the acetylcholinesterase blocker, galantamine, led to a substantial intensification of the impulse activity of the cortical neurons, and at the same time did not exert a substantial influence on the network activity of the same neurons. The hypothesis is advanced that the intracortical neuronal interactions may be accomplished independently of extracortical influences that are expressed in the fluctuations of the baseline impulse activity of individual cells. The qualitative assessment that was carried out of the influence of ACh on the functional characteristics of the cortical neurons does not make it possible to identify an influence of ACh (including a modulatory influence) on the formation of intracortical connections. The methods used in this investigation may be used for a further study of the influence of various mediator systems of the brain on the functioning of intracortical interneuronal connections.

Acetylcholine↗

PubMed1991

Creutzfeldt-Jakob disease--clinical picture analysis.

The early, late, and terminal features of (CJD) were analyzed, based on the clinical histories and picture evolution of 12 histologically-confirmed cases of CJD. The most essential features observed were sensorimotor disintegration, and impairment of both mental and higher cortical functions, occurring in various combinations. On the basis of a sampling of early symptoms and signs we were able to make an early differential diagnosis.

Adult↗

PubMed1993

Effect of unilateral motor cortex ablation on activity of choline acetyltransferase and levels of amino acid transmitter candidates in the spinal cord of adult monkeys.

Evidence that L-glutamate is a neurotransmitter of corticofugal fibers was sought by measuring changes in several biochemical markers of neurotransmitter function in discrete regions of spinal cord after ablation of sensorimotor cortex in monkeys. One and five weeks after unilateral cortical ablation, samples from six areas of spinal cord (ventral, lateral and dorsal regions of the left and right sides) were analysed for choline acetyltransferase (ChAT) activity and contents of amino acid transmitter candidates-glutamic acid (Glu), aspartic acid (Asp), glycine (Gly), taurine (Tau) and gamma-aminobutyric acid (GABA). During one to five weeks after unilateral cortical ablation of the monkey, prolonged hemiplegia in the contralateral side was observed. Histological examination of the spinal cord 5 weeks after unilateral (left) cortical ablation showed no apparent change in either control (ipsilateral, left) or affected (contralateral, right) sides of the cord as examined by the Klüver-Barrera method. The ChAT activity as a cholinergic marker was scarcely changed in any region of either left (control) or right (affected) side of the spinal cord at one and five weeks after unilateral (left side) ablation of the motor cortex. Amino acid levels in each region of the spinal cord were not significantly changed one week after unilateral ablation of the motor cortex. However, a significant decrease of Glu content was observed in the lateral column of the affected (right) side compared to the control (left) side of cervical and lumbar cord five weeks after cortical ablation of the left motor area. No concomitant alterations of other amino acids were detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗

PubMed1985

Topographical dopamine and serotonin distribution and turnover in rat striatum.

Topographic distribution of dopamine (DA), serotonin (5-HT), dihydroxyphenylacetic acid (DOPAC), hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) was determined in rat striatum using high-pressure liquid chromatography (HPLC) with electrochemical detection. The ratios of DOPAC:DA and 5-HIAA:5-HT were calculated as indices of turnover of DA and 5-HT. There was a rostro-caudal gradient for both DA and 5-HT, with DA highest in rostral striatum and 5-HT highest in caudal striatum (P less than 0.01). DA concentrations in the coronal plane showed a homogeneous distribution except at the level of the globus pallidus. DOPAC also showed a rostro-caudal gradient and concentrations were significantly increased in the nucleus accumbens (P less than 0.01). DOPAC:DA ratios were significantly increased in both the nucleus accumbens and the ventromedial striatum as compared to the remaining striatal punches. 5-HT was more heterogeneously distributed in the coronal plane with concentrations highest in the ventromedial and the ventrolateral quadrants, where they were 2-3-fold higher than in dorsal striatum (P less than 0.01). Concentrations of 5-HIAA were highest in the nucleus accumbens and ventromedial striatum but HIAA-5-HT ratios were highest in the dorsolateral striatum (P less than 0.01). DA turnover is therefore highest in limbic innervated (n. accumbens and ventromedial) striatum while 5-HT turnover is highest in sensorimotor innervated (dorsolateral) striatum. These findings provide further evidence for functional compartmentalization within the striatum.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1996

Event-related coherence as a tool for studying dynamic interaction of brain regions.

This paper demonstrates a simple approach to calculating time courses of coherence for data recorded during an event-related paradigm. Event-related coherence (ERCoh) was investigated between left and right sensorimotor areas, and between contralateral sensorimotor and SMA during discrete right index finger movements. It is demonstrated that ERCoh can provide information regarding the dynamic interaction of spatially separated brain regions. In the upper alpha band, the mu rhythm of the contralateral sensorimotor area is shown to be linearly phase-coupled to rhythmic activity recorded over the SMA. This synchrony between the rhythms decreases during planning and execution of movement when the respective areas become active. In the gamma band, a short-lasting increase in coherence is found between the contralateral sensorimotor area and the SMA prior to movement, indicating possible functional interaction of these areas during the final stages of movement preparation.

Electrodes↗

PubMed1980

Peripheral insulin in response to the sight and smell of food.

Twenty-five obese and 23 reference women were compared with respect to their peripheral insulin concentrations in response to the sight and smell of food. An additional 21 obese women were examined for different control purposes. The women were examined after fasting for approximately 16 hr. Venous blood samples for determination of glucose and insulin were drawn 20, 10, and 1 min prior to the demonstration of food for 5 min. After the food had been presented to the subjects, samples were drawn at 1, 2, 3, 4, 5, 6, 10, 15, and 20 min. The response was calculated in two different ways: method I--the difference between meal basal insulin values and mean insulin values during and/or after stimulation, and method II--the "insulin area" over the mean basal concentration was calculated for 0-20 min after start of food presentation. Both methods resulted in significantly higher insulin responses in obese as compared to reference subjects. However, when performing duplicate experiments in the same subjects only method II resulted in reproducible results and even with this method the error was as high as 60%-90%. The high error of the method was partly expected since the insulin elevation is most likely not only a function of controlled external cues but also dependent on unknown sensorimotor and cognitive-affective alterations. No insulin response was observed when obese women were exposed to an external cue that was not food related. Atropine completely blocked the insulin elevation in response to food related external stimuli indicating that this insulin response is mediated via vagus.

Adult↗

PubMed1993

Death of intermediolateral spinal cord neurons follows selective, complement-mediated destruction of peripheral preganglionic sympathetic terminals by acetylcholinesterase antibodies.

Systemically injected anti-acetylcholinesterase antibodies in rats cause selective lesions of preganglionic sympathetic neurons. Adult rats were examined up to four months after a single i.v. injection of murine monoclonal acetylcholinesterase antibodies or normal immunoglobulin G (1.5 mg). Within 4 h, antibody-treated rats developed ptosis, a sign of sympathetic dysfunction that was never reversed. Persistent pupillary constriction reflected preserved and unopposed parasympathetic function. Weight gain was depressed, but locomotor activity, excitability, and sensorimotor responses were normal, and gross neuromuscular performance was near normal. These findings were supported by biochemical evidence for selective sympathetic damage. Acetylcholinesterase activity was reduced for the whole period of observation in sympathetic ganglia and adrenal glands but fell only transiently in muscle and serum. At all times, choline acetyltransferase activity (a marker of presynaptic terminals) was unaffected in muscle but grossly depleted in ganglia. Light and electron microscopy showed that preganglionic sympathetic terminals of superior cervical ganglia were severely damaged while parasympathetic ganglia were less affected and motor endplates of skeletal muscle were apparently spared. Immunocytochemistry revealed punctate deposits of murine immunoglobulin G and complement component C3 in ganglionic neuropil 12 h after antibody injection. This finding was consistent with complement-mediated lysis of preganglionic terminals. Morphometric analysis of preganglionic neurons in the intermediolateral nucleus of the spinal cord showed progressive loss of cholinergic perikarya over several months. We conclude that antibody-induced destruction of ganglionic terminals leads to death of preganglionic sympathetic neurons and, hence, permanent dysautonomia.

Acetylcholinesterase↗

PubMed2006

The role of ventral premotor cortex in action execution and action understanding.

The human ventral premotor cortex overlaps, at least in part, with Broca's region in the dominant cerebral hemisphere, that is known to mediate the production of language and contributes to language comprehension. This region is constituted of Brodmann's areas 44 and 45 in the inferior frontal gyrus. We summarize the evidence that the motor related part of Broca's region is localized in the opercular portion of the inferior frontal cortex, mainly in area 44 of Brodmann. According to our own data, there seems to be a homology between Brodmann area 44 in humans and the monkey area F5. The non-language related motor functions of Broca's region comprise complex hand movements, associative sensorimotor learning and sensorimotor integration. Brodmann's area 44 is also a part of a specialized parieto-premotor network and interacts significantly with the neighbouring premotor areas. In the ventral premotor area F5 of monkeys, the so called mirror neurons have been found which discharge both when the animal performs a goal-directed hand action and when it observes another individual performing the same or a similar action. More recently, in the same area mirror neurons responding not only to the observation of mouth actions, but also to sounds characteristic to actions have been found. In humans, through an fMRI study, it has been shown that the observation of actions performed with the hand, the mouth and the foot leads to the activation of different sectors of Broca's area and premotor cortex, according to the effector involved in the observed action, following a somatotopic pattern which resembles the classical motor cortex homunculus. On the other hand the evidence is growing that human ventral premotor cortex, especially Brodmann's area 44, is involved in polymodal action processing. These results strongly support the existence of an execution-observation matching system (mirror neuron system). It has been proposed that this system is involved in polymodal action recognition and might represent a precursor of language processing. Experimental evidence in favour of this hypothesis both in the monkey and humans is shortly reviewed.

Animals↗

PubMed2004

Motor functions of the Broca's region.

Broca's region in the dominant cerebral hemisphere is known to mediate the production of language but also contributes to comprehension. This region evolved only in humans and is constituted of Brodmann's areas 44 and 45 in the inferior frontal gyrus. There is, however, evidence that Broca's region overlaps, at least in part, with the ventral premotor cortex. We summarize the evidence that the motor related part of Broca's area is localized in the opercular portion of the inferior frontal cortex, mainly in area 44 of Brodmann. According to our own data, there seems to be a homology between Brodmann area 44 in humans and the monkey area F5. The non-language related motor functions of Broca's region comprise complex hand movements, associative sensorimotor learning and sensorimotor integration. Brodmann's area 44 is also a part of a specialized parieto-premotor network and interacts significantly with the neighboring premotor areas.

Animals↗

PubMed2003

Expanding the biological basis of tinnitus: crossmodal origins and the role of neuroplasticity.

Tinnitus is most often initiated by modality specific otopathologic disturbances affecting peripheral and central auditory pathways. However, there is growing evidence indicating that the anatomical location generating tinnitus occurs at sites different from the initial pathology. Support for this notion is found in individuals where tinnitus can be triggered or modulated by inputs from other sensory modalities or sensorimotor systems (somatosensory, somatomotor, visual-motor). The use of functional imaging methods combined with psychophysics, detailed physical examinations and questionnaire-based assessments has reinforced and validated these observations. Available data suggest that tinnitus-related crossmodal interactions are more common than previously anticipated. This communication reviews these advancements and suggests that a relatively broad multimodal network of neurons is involved in generating and sustaining the tinnitus perception in some forms of the disorder. Also implicated as part of the tinnitus experience are interactions within large-scale neural networks subserving attention, cognition, and emotion. Incorporating this knowledge into contemporary psychophysiological models will help facilitate the conceptualization of this phantom perception in a more comprehensive manner.

Animals↗

PubMed2002

Congenital mirror movement: a study of functional MRI and transcranial magnetic stimulation.

Two male patients (a child and an adult) with congenital mirror movement were studied using functional MRI (fMRI) and transcranial magnetic stimulation (TMS). Bilateral primary sensorimotor cortices were activated during unilateral hand gripping on fMRI when the child patient was 8 years old andthe adult was 37 years old. Bilateral motor evoked potentials were induced from the hand and forearm muscles after TMS of each hemisphere. Bilateral motor responses were also induced from the arm muscles in the adult patient. Bilateral motor responses had short and similar latencies. Contralateral motor responses to TMS were smaller than ipsilateral ones in the hand muscles, while contralateral responses were larger than ipsilateral ones in the arm muscles. Contralateral hand motor responses reduced in amplitude or disappeared with increasing age while in the child patient, mirror movements decreased gradually. Our results suggest that bilateral activation of the primary sensorimotor cortices during intended unilateral hand movement and bilateral motor responses to TMS account, at least in part, for the pathophysiology of congenital mirror movement. Reduction of contralateral hand motor responses may be related to the decrease in mirror movements during development.

Adult↗

PubMed2002

What songbirds teach us about learning.

Bird fanciers have known for centuries that songbirds learn their songs. This learning has striking parallels to speech acquisition: like humans, birds must hear the sounds of adults during a sensitive period, and must hear their own voice while learning to vocalize. With the discovery and investigation of discrete brain structures required for singing, songbirds are now providing insights into neural mechanisms of learning. Aided by a wealth of behavioural observations and species diversity, studies in songbirds are addressing such basic issues in neuroscience as perceptual and sensorimotor learning, developmental regulation of plasticity, and the control and function of adult neurogenesis.

Aging↗