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Results for “sensorimotor function”

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PubMed2002

Improving hand function in chronic stroke.

BACKGROUND: Recovery of function following stroke plateaus in about 1 year, typically leaving upper arm function better than that in the hand. Since there is competition among body parts for territory in the sensorimotor cortex, even limited activity of the upper arm might prevent the hand from gaining more control, particularly when the territory is reduced in size because of the stroke. Deafferentation of a body part in a healthy brain enhances cortical representations of adjacent body parts, and this effect is markedly increased by voluntary activity of the adjacent part. OBJECTIVE: To explore whether deafferentation of the upper arm, produced by a new technique of regional anesthesia during hand motor practice, helps recovery of hand function in patients with long-term stable weakness of their hand following stroke. METHODS AND RESULTS: Deafferentation, produced by a new technique of regional anesthesia of the upper arm during hand motor practice, dramatically improved hand motor function including some activities of daily living. The improvement was associated with an increase in transcranial magnetic stimulation-evoked motor output to the practice hand muscles. CONCLUSION: This is a novel therapeutic strategy that may help improve hand function in patients with long-term weakness after stroke.

Afferent Pathways↗

PubMed2004

Evidence for bilateral control of skilled movements: ipsilateral skilled forelimb reaching deficits and functional recovery in rats follow motor cortex and lateral frontal cortex lesions.

Unilateral damage to cortical areas in the frontal cortex produces sensorimotor deficits on the side contralateral to the lesion. Although there are anecdotal reports of bilateral deficits after stroke in humans and in experimental animals, little is known of the effects of unilateral lesions on the same side of the body. The objective of the present study was to make a systematic examination of the motor skills of the ipsilateral forelimb after frontal cortex lesions to either the motor cortex by devascularization of the surface blood vessels (pial stroke), or to the lateral cortex by electrocoagulation of the distal branches of the middle cerebral artery (MCA stroke). Plastic processes in the intact hemisphere were documented using Golgi-Cox dendritic analysis and by intracortical microstimulation analysis. Although tests of reflexive responses in forelimb placing identified a contralateral motor impairment following both cortical lesions, quantitative and qualitative measures of skilled reaching identified a severe ipsilateral impairment from which recovery was substantial but incomplete. Golgi-impregnated pyramidal cells in the forelimb area showed an increase in dendritic length and branching. Electrophysiological mapping showed normal size forelimb representations in the lesioned rats relative to control animals. The finding of an enduring ipsilateral impairment in skilled movement is consistent with a large but more anecdotal literature in rats, nonhuman primates and humans, and suggests that plastic changes in the intact hemisphere are related to that hemisphere's contribution to skilled movement.

Animals↗

PubMed2005

Functional topography of working memory for face or voice identity.

We used functional magnetic resonance imaging (fMRI) to investigate whether the neural systems for nonspatial visual and auditory working memory exhibits a functional dissociation. The subjects performed a delayed recognition task for previously unfamiliar faces and voices and an audiovisual sensorimotor control task. During the initial sample and subsequent test stimulus presentations, activation was greater for the face than for the voice identity task bilaterally in the occipitotemporal cortex and, conversely, greater for voices than for faces bilaterally in the superior temporal sulcus/gyrus (STS/STG). Ventral prefrontal regions were activated by both memory delays in comparison with the control delays, and there was no significant difference in direct voxelwise comparisons between the tasks. However, further analyses showed that there was a subtle difference in the functional topography for two delay types within the ventral prefrontal cortex. Face delays preferentially activate the dorsal part of the ventral prefrontal cortex (BA 44/45) while voice delays preferentially activate the inferior part (BA 45/47), indicating a ventral/dorsal auditory/visual topography within the ventral prefrontal cortex. The results confirm that there is a modality-specific attentional modulation of activity in visual and auditory sensory areas during stimulus presentation. Moreover, within the nonspatial information-type domain, there is a subtle across-modality dissociation within the ventral prefrontal cortex during working memory maintenance of faces and voices.

Attention↗

PubMed2000

Specialized neural systems underlying representations of sequential movements.

The ease by which movements are combined into skilled actions depends on many factors, including the complexity of movement sequences. Complexity can be defined by the surface structure of a sequence, including motoric properties such as the types of effectors, and by the abstract or sequence-specific structure, which is apparent in the relations amongst movements, such as repetitions. It is not known whether different neural systems support the cognitive and the sensorimotor processes underlying different structural properties of sequential actions. We investigated this question using whole-brain functional magnetic resonance imaging (fMRI) in healthy adults as they performed sequences of five key presses involving up to three fingers. The structure of sequences was defined by two factors that independently lengthen the time to plan sequences before movement: the number of different fingers (1-3; surface structure) and the number of finger transitions (0-4; sequence-specific structure). The results showed that systems involved in visual processing (extrastriate cortex) and the preparation of sensory aspects of movement (rostral inferior parietal and ventral premotor cortex (PMv)) correlated with both properties of sequence structure. The number of different fingers positively correlated with activation intensity in the cerebellum and superior parietal cortex (anterior), systems associated with sensorimotor, and kinematic representations of movement, respectively. The number of finger transitions correlated with activation in systems previously associated with sequence-specific processing, including the inferior parietal and the dorsal premotor cortex (PMd), and in interconnecting superior temporal-middle frontal gyrus networks. Different patterns of activation in the left and right inferior parietal cortex were associated with different sequences, consistent with the speculation that sequences are encoded using different mnemonics, depending on the sequence-specific structure. In contrast, PMd activation correlated positively with increases in the number of transitions, consistent with the role of this area in the retrieval or preparation of abstract action plans. These findings suggest that the surface and the sequence-specific structure of sequential movements can be distinguished by distinct distributed systems that support their underlying mental operations.

Adolescent↗

PubMed1995

The role of the left somatosensory cortex in human hand movement.

Hemispheric dominance for motor control in the human brain is still unclear. Here we propose asymmetric sensorimotor integration during human hand movements. We investigated the dexterity of hand movements and related sensory functions in four right-handed patients with cerebrovascular lesions in the postcentral gyrus. To clarify the distributions of cortical damage, semiquantitative analysis of regional cerebral blood flow (rCBF) was performed using single photon emission computed tomography (SPECT), and a three-dimensional surface display was generated from SPECT. Scores on motor and sensory tasks and rCBF values in the patients were compared with those in control subjects. All patients presented with asymmetric clumsiness of complex finger movements, in association with impairments of combined sensations such as stereognosis. These findings were indicative of a disorder of sensory information processing necessary to guide the movements. Two patients with left hemispheric damage showed bilateral clumsy hands, predominating on the right side, while the other two patients with right hemispheric damage showed only a left clumsy hand. In agreement with asymmetric clumsiness, measurement of rCBF along with a three-dimensional surface display revealed cortical hypoperfused areas, mainly in the perirolandic cortices, comprising the primary motor and somatosensory cortices. Perirolandic cortical hypoperfusion was bilateral in the two patients with bilateral clumsy hands, but only on the right side in the other two patients with left clumsy hands. These results suggest a dominant role of the left somatosensory cortex in sensorimotor integration for complex finger movements of humans.

Aged↗

PubMed1985

Neuropsychologic function in children with brain tumors: III. Interval changes in the six months following treatment.

Twenty-six children with primary brain tumors were studied prospectively with regard to their sensorimotor, intellectual, academic, and emotional status. Serial evaluations were conducted after surgery (pre-irradiation) and six months after the completion of radiation therapy. The timing of the second evaluation was chosen so as to antedate the late effects of irradiation. Children over 6 years old displayed significant improvement of intellectual function over time, with only 11% exhibiting deterioration on one or more cognitive parameters. In contrast, 68% of younger children clinically deteriorated in one or more areas of intellectual functioning, with prominent difficulties in memory and selective attention for age. Children under 6 years old with supratentorial tumors were less likely than those with posterior fossa tumors to improve their cognitive performance. At the second evaluation, 23% of the patients were functioning below normal (IQ less than 80) intellectually, with 50% of the younger children and 11% of the older children receiving special educational assistance. Approximately 40-50% of the patients manifested emotional adjustment problems at each evaluation. The results are discussed in terms of the clinical need to follow similar patient populations with formal psychological assessments over time, and in terms of the difficulties involved in defining factors that determine the functional status of children surviving brain tumors.

Achievement↗

PubMed2006

Neural responses to non-native phonemes varying in producibility: evidence for the sensorimotor nature of speech perception.

Neural responses to unfamiliar non-native phonemes varying in the extent to which they can be articulated were studied with functional magnetic resonance imaging (fMRI). Both superior temporal (auditory) and precentral (motor) areas were activated by passive speech perception, and both distinguished non-native from native phonemes, with greater signal change in response to non-native phonemes. Furthermore, speech-responsive motor regions and superior temporal sites were functionally connected. However, only in auditory areas did activity covary with the producibility of non-native phonemes. These data suggest that auditory areas are crucial for the transformation from acoustic signal to phonetic code, but the motor system also plays an active role, which may involve the internal generation of candidate phonemic categorizations. These 'motor' categorizations would then be compared to the acoustic input in auditory areas. The data suggest that speech perception is neither purely sensory nor motor, but rather a sensorimotor process.

Adolescent↗

PubMed1999

Intra-operative optical method using intrinsic signals for localization of sensorimotor area in patients with brain tumor.

The purpose of this study is intra-operatively to localize the sensorimotor area by intrinsic optical method detecting the changes in regional cerebral blood flow (rCBF) and cortical temperature following neuronal activity during median nerve stimulation. In 18 patients with brain tumors located around the sensorimotor cortex, cortical recording of somatosensory evoked potentials (SEPs) was performed and localized changes in rCBF during median nerve stimulation were measured by a laser-Doppler flowmeter on the locations of SEPs and around the activation area obtained by functional magnetic resonance imaging (fMRI). In two patients, cortical thermomapping was also performed during median nerve stimulation. In fMRI study, the significant activation area of sensorimotor could be obtained in 17 of 18 patients. In cortical recording of SEPs, the polarity reversal of N20 and P20 was observed in 14 of the 18 patients. In 9 of the 14 patients in whom SEPs could be recorded, the localized changes in rCBF, corresponding to the stimulation, were detected in the N20 area. In 2 of the 4 patients in whom N20 could not be recorded successfully, the localized changes in rCBF could be detected. The increase in rCBF during the stimulation was 18.3% +/- 5.3% (mean +/- SD, n = 11). Thermomapping could demonstrate the localized area, where the increase in rCBF was also detected, by observation of the changes in cortical temperature during the stimulation. The intra-operative intrinsic optical method detecting rCBF and cortical temperature in combination with recording of SEPs may be considered useful for brain functional localization related to neurosurgical disorders.

Aged↗

PubMed1983

Pure "aphasic" agraphia due to damage of the left superior parietal lobule.

A case of pure agraphia, due to an ischaemic lesion of the left superior parietal lobule, is reported. The neuropsychological analysis of writing performances suggests an aphasic nature of this patient's pure agraphia. The authors discuss the role played by diffuse and/or localized brain lesions in writing function, emphasizing that the left superior parietal lobule in man may be crucial for the sensorimotor linguistic integration needed for writing.

Aged↗

PubMed2004

A compensatory mechanism in unilateral akinetic-rigid syndrome: an fMRI study.

The motor mechanisms of a patient with unilateral hand clumsiness in the early stages of akinetic-rigid syndrome were assessed by functional magnetic resonance imaging (fMRI). Movements of the unaffected hand produced activation in the contralateral sensorimotor cortex (SMC) and ipsilateral SMC and superior parietal lobule (SPL). The affected hand activated the bilateral SMCs, supplementary motor areas, and SPLs. We speculated that the bilateral activation indicated recruitment of a pre-existing bilaterally organized large-scale neural network to perform the motor task.

Aged↗

PubMed2006

Motor imagery and EEG-based control of spelling devices and neuroprostheses.

A brain-computer interface (BCI) transforms signals originating from the human brain into commands that can control devices or applications. With this, a BCI provides a new non-muscular communication channel, which can be used to assist patients who have highly compromised motor functions. The Graz-BCI uses motor imagery and associated oscillatory EEG signals from the sensorimotor cortex for device control. As a result of research in the past 15 years, the classification of ERD/ERS patterns in single EEG trials during motor execution and motor imagery forms the basis of this sensorimotor-rhythm controlled BCI. The major frequency bands of cortical oscillations considered here are the 8-13 and 15-30 Hz bands. This chapter describes the basic methods used in Graz-BCI research and outlines possible clinical applications.

Communication Devices for People with Disabilities↗

PubMed1991

Sparing of function after neonatal frontal lesions correlates with increased cortical dendritic branching: a possible mechanism for the Kennard effect.

This study examined the possibility that the presence or absence of behavioral sparing following neonatal frontal lesions might be correlated with changes in the complexity of dendritic branching. Rats were given bilateral frontal lesions in either adulthood, the day of birth, or on day 10. Ninety days later the animals were trained in a spatial navigation task. The animals' brains were then processed for Golgi-Cox staining and the dendritic branching of the pyramidal cells in the parietal cortex was analyzed. Frontal cortical lesions in newborn rats produced a severe behavioral deficit in the water task whereas frontal removal at 10 days of age allowed sparing of function relative to adult operates (that is, the Kennard effect). Analysis of dendritic arbor in sensorimotor cortex revealed that the day-10 animals exhibited a dramatic proliferation of dendritic arbor relative to control rats. In contrast, the day-1 animals had slightly less dendritic branching than control animals. Rats with frontal lesions in adulthood showed a small, but significant, increase in dendritic branching. The correlation between behavioral sparing and the increase in dendritic arborization following neonatal lesions may be illustrative of a general mechanism underlying the Kennard effect.

Animals↗

PubMed1994

Temporal and kinematic properties of motor behavior reflected in mentally simulated action.

Related perceptual, motor, and cognitive performances were examined to reveal the accuracy of the properties of action spontaneously represented when mentally simulating moving one's hand. The kinematic configuration of the body represented and transformed in mental simulations was not fixed or canonical but corresponded to one's current configuration. Mental simulation time mimicked movement time for natural efficient movement from a posture midway between each of the hand's joint limits into many other postures. Equal time was required for simulated and real movements into more common, comfortable postures; shorter but proportional time was required for simulated movement than real movement into less common postures that involved longer trajectories, coordinated activity at more joints, motion near extremes of joint limits, and uncomfortable kinesthetic sensations. The findings suggest that sensorimotor structures support mental simulations of actions.

Functional Laterality↗

PubMed2006

Neurobehavioral and immunological consequences of prenatal immune activation in rats. Influence of antipsychotics.

Increasing evidence suggests that pre- or perinatal events that influence the immune system contribute to the development of behavioral or neuropsychiatric disorders. For instance, exposure of pregnant rats to the bacterial endotoxin lipopolysaccharide (LPS) disrupts sensorimotor information processing, as assessed by the prepulse inhibition test (PPI), and also the immune function in adult offspring, which might be of particular relevance as regards schizophrenia. However, the consequences of maternal LPS exposure during pregnancy on synaptic functioning in adult offspring and, more importantly, the therapeutic opportunity to re-establish PPI and immune function have still to be demonstrated. In this work, we analyzed the consequences of prenatal LPS exposure on dopaminergic neurotransmission and presynaptic markers in adult brain areas related to PPI circuitry. In addition, we tested whether oral treatment with the typical antipsychotic drug haloperidol (HAL) could reinstate PPI performances and cytokine serum levels in six-month-old male rats with prenatal LPS exposure. Both sensory information processing deficits and immune anomalies induced by prenatal exposure to LPS were accompanied by changes in dopaminergic neurotransmission and synaptophysin expression. It is important to note that PPI disruption and serum increases in cytokines induced by prenatal LPS exposure were both reversed by HAL. Taken together, these results demonstrate the critical influence of prenatal immune events on the functioning of adult nervous and immune systems, in association with the putative role of the immune system in the development of behavior relevant to schizophrenia.

Analysis of Variance↗

PubMed2002

Perception of self-generated action in schizophrenia.

INTRODUCTION: Self-generated actions involve central processes of sensorimotor integration that continuously monitor sensory inputs to ensure that motor outputs are congruent with our intentions. This mechanism works automatically in normal conditions but becomes conscious whenever a mismatch happens during the execution of action between expected and current sensorimotor reafferences. It is now admitted in the literature that sensorimotor processes as well as the ability to predict the consequences of our own actions imply the existence of a forward model of action, which is based on efference copies. Recently, it has been proposed that positive symptoms expressed by schizophrenic patients, such as delusions of control or thought insertions, arise because of a deficiency in this forward model, and more particularly, because of a lack of awareness of certain aspects of motor control derived from such an internal model. METHOD: To test further this hypothesis, 19 schizophrenic patients (10 with and 9 without Schneiderian symptoms) and 19 control subjects performed a visuo-motor conflict task and had verbally to report the felt position of their hand at the end of each trial. RESULTS: Under this experimental procedure, schizophrenic patients--whatever their clinical phenotype--failed to switch to a conscious representation of their hand movements, and then consequently to maintain their level of performance for the sensorimotor adjustment in comparison with controls. CONCLUSION: Our findings suggest two facts. First, that a functional monitoring of action, based on a forward.

Journal Article↗

PubMed2003

Cortical reorganization induced by task-oriented training in chronic hemiplegic stroke patients.

We investigated the effect of task-oriented training (TT) on the cortical activation pattern in four chronic hemiparetic stroke patients. A TT program, consisting of six tasks, which were designed to improve hemiparetic upper extremity function, was performed for 40 min/day, 4 days/week for 4 weeks. The functional status of the affected hand and fMRI were assessed before and after the TT program. fMRI was performed at 1.5 T in parallel with timed finger flexion-extension exercises at a fixed rate. The main cortical activation changes with functional recovery were a decrease in the unaffected and an increase in the affected primary sensorimotor cortex activities. In conclusion, it seems that cortical reorganization was induced by the TT program in chronic hemiparetic stroke patients.

Adult↗

PubMed2006

Rationale for a model of human systems integration: the need of a theoretical framework.

Human systems integration (HSI) involves augmented human design with the objectives of augmenting human capabilities and improving human performance using behavioral technologies. The fundamental matter of human systems integration and augmented human design is the organization and the nature of interactions that couple physiological systems, humans- and engineered systems, artifacts. By this definition, augmented human consists of interactive artefacts linked to physiological systems. This paper focuses on the rationale of a HSI model based on specific experiments (comparison of dynamical sensorimotor integration and motor performances in real and virtual environments) that confirm the hypothesis of functional interaction in the framework of Chauvet's mathematical theory of integrative physiology (MTIP). Epistemological constraints for HSI and the role of MTIP are briefly discussed in this context.

Adult↗

PubMed1986

The pathophysiology of dementia.

Dementia is a symptom of a variety of specific structural brain diseases as well as several system degenerations. Alzheimer's disease presently is the commonest cause in the developed world, causing a cortical-subcortical degeneration of ascending cholinergic neurons and large pyramidal cells in the cerebral cortex. Clinically, the disease reflects predominantly deterioration of function in the association cortex. Pharmacologically and pathologically, abnormalities are more diffuse and extend into sensorimotor cortical areas as well.

Aged↗