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Results for “sensorimotor function”

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PubMed1992

Responses of rat substantia nigra pars reticulata units to cortical stimulation.

In order to study the function of multiple pathways between the sensorimotor cortex (Cx) and the substantia nigra pars reticulata (SNr), responses of SNr units to stimulation of the Cx were studied in anesthetized rats. Most of the units (229 of 236) exhibited repetitive firing with fairly short, regular intervals. The other 7 units displayed long duration spikes, irregular firing intervals and slow spontaneous firing. Stimulation of the Cx usually resulted in a short latency excitation and occasionally a long latency inhibition in both types of units. When strong stimulation was applied, multiple excitatory and inhibitory responses alternating each other with about a 25 ms interval were observed. SNr units responded with different patterns and latencies to stimulation of different sites of the sensorimotor Cx. The results indicate that signals derived from the sensorimotor Cx reach the SNr via multiple pathways and converge on many SNr neurons.

Animals↗

PubMed2002

Spinal reflexes provide motor error signals to cerebellar modules--relevance for motor coordination.

The cerebellar olivo-cortico-nuclear network influencing rubro- and corticospinal tracts via the nucleus interpositus anterior (NIA) is one of the most thoroughly characterized mammalian motor systems involved in limb movement control. Recent findings indicate that climbing fibres innervating the NIA system mediate highly integrated sensorimotor information derived from spinal withdrawal reflex modules. In the present paper, the implications of this relationship between spinal and cerebellar neuronal networks for cerebellar sensorimotor processing are put in perspective of the modular organization of the NIA system. Data that should prove useful for computational models of cerebellar sensorimotor processing and motor learning, including functional spino-olivo-cortico-nucleo-spinal connectivity, are reviewed. It is argued that spinal 'pre-processing' of climbing fibre input constitutes a signal conversion from 'sensory' to 'motor' coordinates, providing the cerebellar modules with motor error signals relevant to the action of single limb muscles. Drawing upon their patterns of interconnectivity with spinal reflex modules it is hypothesized how cerebellar modules may adaptively coordinate transitions between agonist and antagonist muscle activity. This mechanism would contribute to the generation of the triphasic EMG patterns that are necessary for smooth acceleration and deceleration of single-joint movements.

Animals↗

PubMed1999

Mu rhythm modulation during changes of visual percepts.

Cooperation between vision and somatomotor behavior, such as manual exploration of objects, suggests close functional coupling between the visual and sensorimotor systems. We observed this type of interaction in human volunteers during binocular rivalry while following the level of sensorimotor mu rhythm with a whole-scalp neuromagnetometer. The observers viewed a weak vertical grating in the lower visual field of one eye and a strong horizontal grating in the same spatial window of the other eye. When stationary, the weak grating was permanently invisible because of its low contrast and spatial frequency. A sudden brief drifting movement of the weak grating wiped out the dominant grating, and the weak grating became visible for less than the 3-s interval between the movements. The postcentral 8- to 15-Hz mu rhythm was found in six of nine observers, and its level increased transiently by 10-15%, starting about 450 ms after the beginning of the movement. The mu level was also enhanced by the actual disappearance of the stronger stimulus, when it occurred in random order with the rivalry stimuli. Identical visual motion, when not accompanied by a perceptual dominance change, produced only minor effects on the mu rhythm. Our results show that a change in visual percept, even with no real or imagined motor response, is associated with modified activity of the postcentral gyrus. This modification may reflect visuohaptic interactions and/or activity of the distributed cortical network implementing visually guided movements.

Adult↗

PubMed2001

Changes in corticomotor representations induced by prolonged peripheral nerve stimulation in humans.

OBJECTIVE: Manipulation of afferent input can induce reorganization within the sensorimotor cortex which may have important functional consequences. Here we investigate whether prolonged peripheral nerve stimulation can induce reorganization within the human motor cortex. METHODS: Using transcranial magnetic stimulation, we mapped the scalp representation of the corticospinal projection to hand muscles in 8 normal subjects before and after 2h of simultaneous repetitive electrical stimulation of the ulnar and radial nerves at the wrist. Control mapping experiments were conducted in 6 subjects. RESULTS: Following nerve stimulation, larger motor-evoked potentials were evoked from more scalp sites. The induced changes were most apparent in first dorsal interosseous, but were also seen in other hand muscles. The increases in area of the representational maps were accompanied by changes in the location of the optimal site for evoking responses in first dorsal interosseous, and changes in the centres of gravity of the maps. CONCLUSIONS: Prolonged afferent stimulation induces an increase in excitability of the corticospinal projection. This is accompanied by a significant shift in the centre of gravity of the stimulated muscles which we propose is evidence of a non-uniform expansion in their cortical representation.

Adult↗

PubMed1996

Role of posterior parietal cortex in the recalibration of visually guided reaching.

Visually guided reaching requires complex neural transformations to link visual and proprioceptive inputs with appropriate motor outputs. Despite the complexity of these transformations, hand-eye coordination in humans is remarkably flexible, as demonstrated by the ease with which reaching can be adapted to distortions in visual feedback. If subjects attempt to reach to visual targets while wearing displacing prisms, they initially misreach in the direction of visual displacement. Given feedback about their reaching errors, however, they quickly adapt to the visual distortion. This is shown by the gradual resumption of accurate reaching while the prisms remain in place, and by the immediate onset of reaching errors in the opposite direction after the prisms have been removed. Despite an abundance of psychophysical data on adaptation to prisms, the functional localization of this form of sensorimotor adaptation is uncertain. Here we use positron emission tomography (PET) to localize changes in regional cerebral blood flow (rCBF) in subjects who performed a prism-adaptation task as well as a task that controlled for the sensory, motor and cognitive conditions of the adaptation experiment. Difference images that reflected the net effects of the adaptation process showed selective activation of posterior parietal cortex contralateral to the reaching limb.

Adaptation, Physiological↗

PubMed2006

Differential recovery of multimodal MRI and behavior after transient focal cerebral ischemia in rats.

The association between recovery of brain function and behavior after transient cerebral ischemia in animals and humans is incompletely characterized. Quantitative diffusion- (DWI), perfusion- (PWI), T(2)-weighted (T(2)WI), and functional magnetic resonance imaging (fMRI) were performed before, during, and up to 1 day after 20-mins transient middle cerebral artery occlusion (tMCAO; n=6) or sham operation (n=6) in male Sprague-Dawley rats. Viability thresholds were employed to calculate diffusion, perfusion, and T(2) lesion volumes. Region of interest analysis was used to evaluate structural and functional MR signal changes within the sensorimotor network, which were then related to corresponding behavioral measures. Post-mortem 2,3,5-triphenyltetrazolium chloride (TTC) staining was performed 24 h after ischemia. Transient middle cerebral artery occlusion produced lesions on DWI and PWI, which fully recovered by 30 mins after reperfusion. Ipsilesional fMRI responses to hypercapnia and forepaw stimulation were significantly impaired after ischemia and did not fully normalize until 3 and 24 h after tMCAO, respectively. No abnormalities were observed on imaging or TTC at 24 h despite significant behavioral dysfunctions including contralesional forelimb impairment and ipsilesional neglect. No MRI, behavioral, or TTC anomalies were observed in sham-operated rats. There were no significant correlations between MRI parameters, behavior, and TTC in either group. Together, these results suggest that normal findings on diffusion, perfusion, and T(2) imaging shortly after transient ischemia may not indicate normal tissue status as indicated by fMRI and behavior, which may help explain the persistence of neurologic deficits in patients with normal conventional MRI after cerebral ischemia.

Animals↗

PubMed1982

Cognition and language development in autism.

A nonverbal assessment procedure was designed to characterize cognition using a Piagetian framework. Six autistic children, five echolalic and one nonverbal, ranging in age from 4:8 to 15:2, participated in this study. Cognitive and language performance was assessed using a developmental stage model. All six children evidenced competence beyond sensorimotor Stage VI, and demonstrated cognitive functioning between the periods of early preoperational and concrete operations. For five of the six children, the stage of cognitive development exceeded that of language development. The application of a developmental model for assessment purposes and theoretical implications of the results are discussed.

Adolescent↗

PubMed1995

Benzodiazepine-insensitive mice generated by targeted disruption of the gamma 2 subunit gene of gamma-aminobutyric acid type A receptors.

Vigilance, anxiety, epileptic activity, and muscle tone can be modulated by drugs acting at the benzodiazepine (BZ) site of gamma-aminobutyric acid type A (GABAA) receptors. In vivo, BZ sites are potential targets for endogenous ligands regulating the corresponding central nervous system states. To assess the physiological relevance of BZ sites, mice were generated containing GABAA receptors devoid of BZ sites. Following targeted disruption of the gamma 2 subunit gene, 94% of the BZ sites were absent in brain of neonatal mice, while the number of GABA sites was only slightly reduced. Except for the gamma 2 subunit, the level of expression and the regional and cellular distribution of the major GABAA receptor subunits were unaltered. The single channel main conductance level and the Hill coefficient were reduced to values consistent with recombinant GABAA receptors composed of alpha and beta subunits. The GABA response was potentiated by pentobarbital but not by flunitrazepam. Diazepam was inactive behaviorally. Thus, the gamma 2 subunit is dispensable for the assembly of functional GABAA receptors but is required for normal channel conductance and the formation of BZ sites in vivo. BZ sites are not essential for embryonic development, as suggested by the normal body weight and histology of newborn mice. Postnatally, however, the reduced GABAA receptor function is associated with retarded growth, sensorimotor dysfunction, and drastically reduced life-span. The lack of postnatal GABAA receptor regulation by endogenous ligands of BZ sites might contribute to this phenotype.

Animals↗

PubMedDate not supplied

The Mary Sheridan Unit: an evaluation of the effects of a hospital unit on the development of visually-impaired multiply handicapped children.

The evidence in this study appears to indicate that adopting a goal-planning approach can provide demonstrable and clear improvements in the developmental functioning of multiply handicapped blind children. However, while the improvements in functioning for self-help and sensorimotor abilities are quite significant, those for communication and language skills are much less so. Three possible hypotheses have been advanced as to why this should be so. The hypothesis that the setting might be an institutionalizing one was rejected on the grounds that some of the evidence did not fit with that from other populations. The second hypothesis referred to the lack of formal speech and communication training on the unit. The best possible test of this hypothesis would be to employ a speech therapist to work on the unit and support for such a scheme is being sought. Finally, it was hypothesized that the way in which the staff interacted with the children was not being sufficiently modified to take account of the children's handicaps.

Activities of Daily Living↗

PubMed2004

Properties of an adult spinal sensorimotor circuit shaped through early postnatal experience.

During development, information about the three-dimensional shape and mechanical properties of the body is laid down in the synaptic connectivity of sensorimotor systems through adaptive mechanisms. This functional adaptation occurs through alteration of connection properties. Here, we characterize the differences between strong and weak connections in the nociceptive withdrawal reflex in adult decerebrate spinal rats, representing the preserved end product of the developmental adaptation process. Stronger excitatory reflex connections from the skin onto a muscle had relatively higher gain in their input-output relations, shorter onset latencies (up to approximately 150 ms) and lower trial-to-trial variability in relation to response amplitude (SD approximately mean(1/2)) than weaker pathways. Although inhibitory and excitatory nociceptive receptive fields of a muscle overlap to some degree, the results indicate that the inhibitory input is not a major determinant of the gain distribution within the excitatory receptive field and vice versa. The N-methyl-D-aspartate (NMDA) receptor antagonist, D-2-amino-5-phosphonovalerate (0.1-1 microg), applied topically on the spinal cord reduced the gain, whereas the response amplitude was mainly reduced by an absolute number by the alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptor antagonist, 6-nitro-7-sulfamoylbenzo(f)quinoxaline-2,3-dione (1-10 microg). The results indicate that NMDA receptors have a critical role in gain regulation in the nociceptive withdrawal reflex system. It is suggested that after normal postnatal experience-dependent adaptation, the number of connections from a given skin site onto the reflex encoding interneurons is a major determinant of the difference in gain.

Animals↗

PubMed2001

Multisensory cortical signal increases and decreases during vestibular galvanic stimulation (fMRI).

Functional magnetic resonance imaging blood-oxygenation-level-dependent (BOLD) signal increases (activations) and BOLD signal decreases ("deactivations") were compared in six healthy volunteers during galvanic vestibular (mastoid) and galvanic cutaneous (neck) stimulation in order to differentiate vestibular from ocular motor and nociceptive functions. By calculating the contrast for vestibular activation minus cutaneous activation for the group, we found activations in the anterior parts of the insula, the paramedian and dorsolateral thalamus, the putamen, the inferior parietal lobule [Brodmann area (BA) 40], the precentral gyrus (frontal eye field, BA 6), the middle frontal gyrus (prefrontal cortex, BA 46/9), the middle temporal gyrus (BA 37), the superior temporal gyrus (BA 22), and the anterior cingulate gyrus (BA 32) as well as in both cerebellar hemispheres. These activations can be attributed to multisensory vestibular and ocular motor functions. Single-subject analysis in addition showed distinctly nonoverlapping activations in the posterior insula, which corresponds to the parieto-insular vestibular cortex in the monkey. During vestibular stimulation, there was also a significant signal decrease in the visual cortex (BA 18, 19), which spared BA 17. A different "deactivation" was found during cutaneous stimulation; it included upper parieto-occipital areas in the middle temporal and occipital gyri (BA 19/39/18). Under both stimulation conditions, there were signal decreases in the somatosensory cortex (BA 2/3/4). Stimulus-dependent, inhibitory vestibular-visual, and nociceptive-somatosensory interactions may be functionally significant for processing perception and sensorimotor control.

Acoustic Stimulation↗

PubMed2005

Structural covariance in the human cortex.

The morphology of the human cortex varies remarkably across individuals, regardless of overall brain size. It is currently unclear whether related cortical regions covary in gray matter density, as a result of mutually trophic influences or common experience-related plasticity. We acquired a structural magnetic resonance imaging scan from 172 subjects and extracted the regional gray matter densities from 12 readily identifiable regions of interest involved in sensorimotor or higher-order cognitive functions. We then used these values to predict regional densities in the remaining areas of the cortex, using voxel-based morphometry. This revealed patterns of positive and negative covariance that provide insight into the topographical organization of multiple cortical regions. We report that the gray matter density of a region is a good predictor of the density of the homotopic region in the contralateral hemisphere, with the striking exception of primary visual cortex. Whereas some regions express patterns of regional covariance that are mirror symmetrical relative to the interhemispheric fissure, other regions express asymmetric patterns of regional covariance. Finally, patterns of covariance are remarkably consistent between males and females, with the exception of the left amygdala, which is positively associated with the left and right anterior inferior temporal cortex in males and with the right angular gyrus in females. Our study establishes that the density of different cortical regions is coordinated within an individual. The coordinated variations we report are likely to be determined by both genetic and environmental factors and may be the basis for differences in individual behavior.

Adult↗

PubMed2005

Sensory and motor neuropathy in a Border Collie.

A 5-month-old female Border Collie was evaluated because of progressive hind limb ataxia. The predominant clinical findings suggested a sensory neuropathy. Sensory nerve conduction velocity was absent in the tibial, common peroneal, and radial nerves and was decreased in the ulnar nerve; motor nerve conduction velocity was decreased in the tibial, common peroneal, and ulnar nerves. Histologic examination of nerve biopsy specimens revealed considerable nerve fiber depletion; some tissue sections had myelin ovoids, foamy macrophages, and axonal degeneration in remaining fibers. Marked depletion of most myelinated fibers within the peroneal nerve (a mixed sensory and motor nerve) supported the electrodiagnostic findings indicative of sensorimotor neuropathy. Progressive deterioration in motor function occurred over the following 19 months until the dog was euthanatized. A hereditary link was not established, but a littermate was similarly affected. The hereditary characteristic of this disease requires further investigation.

Animals↗

PubMed1987

Body schema and identity.

The author describes the body schema as the representation of the body in the mind which is organized throughout the process of development and has the characteristics of an internal object. She describes it as constantly fluctuating between the levels of symbol and of symbolic equation. As to the genesis of the body schema, she describes the relationship of the child with its parents and, in particular, with the mother, as the site of origin of the body schema. She also mentions the importance of the functioning body and hence of the sensorimotor period for the development of the body schema and of self-object differentiation. Finally, discussing body schema and identity, she describes the relations between these two entities and with the self, as relationships of mutual containment and representation. She relates these concepts to Klein's theory of the "assembly of internalized objects'. She then turns to psychopathology, which she regards as the results of a mutual invasion between the body schema, identity and the self. She gives a number of clinical examples to illustrate various aspects of psychopathology and of the relations between body schema and identity.

Anorexia Nervosa↗

PubMedDate not supplied

[Conjugation of unit activity in the visual and sensomotor areas of the rabbit neocortex during a conditioned reflex to sound and light].

Conjugation of unit activity in the visual and sensorimotor neocortical areas was studied by means of histograms of cross- and autocorrelation in rabbits with conditioned reflex to light (1st group) and sound (2nd group). Relative number of neurones pairs acting in correlation in the areas remote from each other, in intersignal intervals both before and after stimuli did not differ in the 1st and 2nd groups. At the same time delays in neuronal discharges in one area after the other were different. In the 1st group animals there was a predominance of the number of visual area neurones discharging after sensorimotor with a delay up to 125 ms, in comparison with the number of sensorimotor area neurones discharging after the visual one. In the 2nd group rabbits the number of visual area neurones with such a delay of discharges after sensorimotor was less and, on the contrary, a predominance of sensorimotor area neurones was observed discharging after the visual one. The obtained results allow to suggest that neurones of the visual and sensorimotor neocortex areas form a single functional system in cases when conditioned and unconditioned stimuli are addressed to these areas and when only one of the studied areas is the projection zone for the combined stimuli. Organization of the neurones activity in systems in these two cases is different.

Animals↗

PubMed1994

[Psychosomatic aspects of focal dystonia: two case reports].

Dystonic movements and other dyskinesias often cause diagnostic difficulties due to their complex symptomatology. Namely focal dystonias are frequently misdiagnosed as conversion reactions. Idiopathic dystonias are generally considered a nonstructural (neurobiochemical) disorder of the basal ganglia. Many case reports, however, have dealt with patients presenting with "atypical" dystonia whose symptoms were relieved by psychotherapy or hypnosis. We present the histories of two young women exhibiting focal dystonia emerging for the first time under circumstances of profound emotional trouble. We discuss the general difficulties in the diagnosis of dystonic movement disorders and review the criteria for the diagnosis of "psychogenic dystonia". The basal ganglia integrate limbic, proprioceptive and sensorimotor inputs to create emotionally and functionally appropriate voluntary movements. Therefore, the traditional dichotomy "psychogenic-somatogenic" appears to be inappropriate when applied to extrapyramidal movement disorders. In a psychosomatic understanding, the assumption of a psychogenic "trigger" for a somatic movement disorder does not mean a contradiction.

Adolescent↗

PubMed1998

Morphologic characteristics of physiologically defined neurons in the cat trigeminal nucleus principalis.

Although the principalis nucleus (Vp) contains trigeminothalamic and internuclear tract cells, the functional and morphologic differences between the two kinds of neurons have remained unsettled. The present study was aimed to address these problems by using the intracellular horseradish peroxidase injection technique in the cat. Of 20 neurons stained, 7 and 13 were located in the dorsomedial subnucleus (Vpd) and ventrolateral subnucleus (Vpv) of Vp, respectively. The Vpd neurons received input from the intraoral structures only but the Vpv neurons from the intraoral or facial structures. Nineteen neurons could be divided as class I and class II, based on the branching pattern of their stem axons. Class I (eight neurons) had an ascending stem axon without branching. Class II was divided into two subclasses (IIa and IIb). Class IIa (eight neurons) had an ascending stem axon from which branches were given off. Their branches formed a local-circuit restricted to the lower brainstem. Class IIb (three neurons) had a stem axon that formed the local-circuit only. The dendritic morphology was indistinguishable between different classes of neurons and between the subdivisions. Although the dendritic arborization pattern was governed by the location of the somata, it was suggested to be also important elements for determining primary afferent arborizations. In the brainstem nuclei, the jaw-closing motor nucleus received the highest density of projections from class II neurons with the receptive field involving the periodontal ligaments. The present study provides new findings that Vp neurons could be divided into three distinct populations and suggests that each population exerts a distinct function with respect to sensory discrimination, sensorimotor reflexes, or both.

Anatomy, Artistic↗

PubMed2005

Brain motor system function after chronic, complete spinal cord injury.

Most therapies under development to restore motor function after spinal cord injury (SCI) assume intact brain motor functions. To examine this assumption, 12 patients with chronic, complete SCI and 12 controls underwent functional MRI during attempted, and during imagined, right foot movement, each at two force levels. In patients with SCI, many features of normal motor system function were preserved, however, several departures from normal were apparent: (i) volume of activation was generally much reduced, e.g. 4-8% of normal in primary sensorimotor cortex, in the setting of twice normal variance in signal change; (ii) abnormal activation patterns were present, e.g. increased pallido-thalamocortical loop activity during attempted movement and abnormal processing in primary sensorimotor cortex during imagined movement; and (iii) modulation of function with change in task or in force level did not conform to patterns seen in controls, e.g. in controls, attempted movement activated more than imagined movement did within left primary sensorimotor cortex and right dorsal cerebellum, while imagined movement activated more than attempted movement did in dorsolateral prefrontal cortex and right precentral gyrus. These modulations were absent in patients with SCI. Many features of brain motor system function during foot movement persist after chronic complete SCI. However, substantial derangements of brain activation, poor modulation of function with change in task demands and emergence of pathological brain events were present in patients. Because brain function is central to voluntary movement, interventions that aim to improve motor function after chronic SCI likely also need to attend to these abnormalities of brain function.

Adult↗