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PubMed1999

Cerebral midline structures in bimanual coordination.

In six healthy right-handed volunteers, we compared the cerebral activation pattern related to unimanual right- and left-hand movements and to bimanual in-phase and anti-phase movements using functional magnetic resonance imaging (fMRI). Internally paced unimanual finger-to-thumb opposition movements led to a strong contralateral activation of primary sensorimotor areas in all six subjects. Midline activity was lateralized to the left side during right-hand movements, but to both sides during left-hand movements. Activity patterns of bimanual in-phase movements resembled the combined activity patterns of the two unimanual conditions: right and left hemispheric activations of the primary sensorimotor cortices and predominantly left-sided medial frontal activity. In contrast, during anti-phase movements, we observed a clear increase in activity, in both right and left frontal midline areas and in right hemispheric, mainly dorsolateral premotor areas compared to in-phase movements. These results indicate that frontal midline activity is not specific for bimanual movements per se. It can already be involved during simple unimanual movements but becomes progressively more involved during more complex aspects of movement control.

Adult↗
PubMed2002

Motor cortex activation is related to force of squeezing.

Primate studies have demonstrated that motor cortex neurons show increased activity with increased force of movement. In humans, this relationship has received little study during a power grip such as squeezing, and has previously only been evaluated across a narrow range of forces. Functional MRI was performed in eight healthy subjects who alternated between rest and right hand squeezing at one of three force levels. During scanning, motor performances were recorded using a dynamometer. At each force level, activation volume was measured within left sensorimotor cortex, right sensorimotor cortex, and a midline supplementary motor area. In left sensorimotor cortex, % signal change was also assessed. The range of force generated across the three force levels varied from 4.9 N to 276 N. In left sensorimotor cortex, activation volume increased significantly with greater force. The % signal change also increased with greater force and correlated closely with activation volume. In supplementary motor area, activation volume increased significantly with increasing force, but with greater intersubject variability. In right sensorimotor cortex, a trend for larger activation volumes with greater force did not reach significance. The laterality index, an expression of the relative degree of contralateral vs. ipsilateral sensorimotor cortex activation, did not change across the three force levels. Increased force of squeezing is associated with increased contralateral sensorimotor cortex and supplementary motor area activation. This relationship was found across the full spectrum of forces that the human hand is capable of generating. Use of a valid, reliable method for assessing motor behavior during functional MRI may be important to clinical applications.

Adult↗
PubMed2006

The neural basis of motor sequencing: an fMRI study of healthy subjects.

The present study used functional MRI to clarify the brain regions activated during a series of motor sequencing tasks in healthy volunteers. Ten subjects were scanned while performing three soft signs tasks ranging from simple (PT: palm tapping), moderate (PS: pronation/supination) to complex movements (FEP: fist-edge-palm). The FEP task induced significant activations within the cortical networks including bilateral sensorimotor, SMA, left parietal, and right cerebellum, but no activation in the prefrontal area. Moreover, the percentage signal changes within the left sensorimotor, left thalamus and right cerebellum showed an increase in activation with task complexity. The present findings challenge the traditional belief that FEP was a task for frontal lobe function but suggest that successful performance of more complex neurological soft sign tasks like FEP requires the participation of more brain areas than simple motor sequencing and coordination task like PS and PT. These also provide the empirical data on the neural basis of neurological soft signs for further study in other clinical group like schizophrenia in the near future.

Adult↗
PubMed1994

Rat posterior parietal cortex: topography of corticocortical and thalamic connections.

Anatomical and functional findings support the contention that there is a distinct posterior parietal cortical area (PPC) in the rat, situated between the rostrally adjacent hindlimb sensorimotor area and the caudally adjacent secondary visual areas. The PPC is distinguished from these areas by receiving thalamic afferents from the lateral dorsal (LD), lateral posterior (LP), and posterior (Po) nuclei, in the absence of input from the ventrobasal complex (VB) or dorsal lateral geniculate (DLG) nuclei. Behavioral studies have demonstrated that PPC is involved in spatial orientation and directed attention. In the present study we used fluorescent retrograde axonal tracers primarily to investigate the cortical connections of PPC, in order to determine the organization of the circuitry by which PPC is likely to participate in these functions, and also to determine how the topography of its thalamic connections differs from that of neighboring cortical areas. The cortical connections of PPC involve the ventrolateral (VLO) and medial (MO) orbital areas, medial agranular cortex (area Fr2), portions of somatic sensory areas Par1 and Par2, secondary visual areas Oc2M and Oc2L, auditory area Te1, and retrosplenial cortex. The secondary visual areas Oc2L and Oc2M have cortical connections which are similar to those of PPC, but are restricted within orbital cortex to area VLO, and within area Fr2 to its caudal portion, and do not involve auditory area Te1. The cortical connections of hindlimb cortex are largely restricted to somatic sensory and motor areas. Retrosplenial cortex, which is medially adjacent to PPC, has cortical connections that are prominent with visual cortex, do not involve somatic sensory or auditory cortex, and include the presubiculum. We conclude that PPC is distinguished by its pattern of cortical connections with the somatic sensory, auditory and visual areas, and with areas Fr2, and VLO/MO, in addition to its exclusive thalamic connectivity with LD, LP and Po. Because recent behavioral studies indicate that PPC, Fr2 and VLO are involved in directed attention and spatial learning, we suggest that the interconnections among these three cortical areas represent a major component of the circuitry for these functions in rats.

Animals↗
PubMed2005

Functional magnetic resonance imaging at 3T as a clinical tool in patients with intracranial tumors.

PURPOSE: To investigate the potential of functional magnetic resonance imaging (fMRI) at 3T as a clinical tool in the preoperative evaluation of patients with intracranial tumors. High magnetic field strength such as 3T is of benefit for fMRI because signal-to-noise ratio and sensitivity to susceptibility changes are field-strength-dependent. MATERIAL AND METHODS: Twenty patients with tumors close to eloquent sensorimotor or language areas were studied. Motor, sensory, and two language paradigms (word generation, rhyming) were used; their effectiveness was determined as the percentage of patients in whom the functional area of interest was activated. Activation maps were calculated and their quality rated as high, adequate, or insufficient. The influence of fMRI on the neurosurgical decision regarding operability, surgical approach, and extent of the resection, was assessed. RESULTS: Paradigm effectiveness was 90% for motor and 95% for sensory stimulation, and varied from 79% to 95% for word generation and rhyming in combination. Ninety percent of the activation maps held high or adequate quality. fMRI proved useful: in the decision to operate (9 patients), in the surgical approach (13 patients), and in extent of the resection (12 patients). CONCLUSION: fMRI at 3T is a clinically applicable tool in the work-up of patients with intracranial tumors.

Adult↗
PubMed1991

The role of sensorimotor experience in object recognition. A case of multimodal agnosia.

Object recognition was studied in a 19-yr-old male patient who presented severe multimodal amnesia and agnosia without significant intellectual, linguistic or perceptual deficits. Bilateral temporal lobe lesions involved medial, polar and anterior infero-temporal structures. Although visual recognition was impaired to various extents for all categories of objects, preservation of certain capacities were demonstrated. In particular, the patient was able to determine specifically how to manipulate certain objects, in spite of his incapacity to define their function or their context of utilization. It is argued that object recognition involves different processing modes such that when direct access to representations of an object is impaired, sensorimotor information activated via alternative cortical and subcortical pathways may provide a limited mechanism for recognition.

Adult↗
PubMed2005

Virtual reality-induced cortical reorganization and associated locomotor recovery in chronic stroke: an experimenter-blind randomized study.

BACKGROUND AND PURPOSE: Virtual reality (VR) is a new promising computer-assisted technology to promote motor recovery in stroke patients. VR-induced neuroplasticity supporting locomotor recovery is not known. We investigated the effects of VR intervention on cortical reorganization and associated locomotor recovery in stroke patients. METHODS: Ten chronic stroke patients were assigned randomly to either the control group or the VR group. VR was designed to provide interactive real-life practice environments in which practice parameters can be individualized to optimize motor relearning. Laterality index (LI) in the regions of interests (ROIs) and locomotor recovery were measured before and after VR using functional MRI (fMRI) and standardized locomotor tests, respectively. The t test and nonparametric test were performed to compare the mean differences at P<0.05. RESULTS: There was a significant difference in the interval change in the LI score for the primary sensorimotor cortex (SMC) between the groups (P<0.05), indicating that VR practice produced a greater increase in LI for the control group. However, the interval changes in the other ROIs were not significantly different (P>0.05). Motor function was significantly improved after VR (P<0.05). CONCLUSIONS: Our novel findings suggest that VR could induce cortical reorganization from aberrant ipsilateral to contralateral SMC activation. This enhanced cortical reorganization might play an important role in recovery of locomotor function in patients with chronic stroke. This is the first fMRI study in the literature that provides evidence for neuroplasticity and associated locomotor recovery after VR.

Brain↗
PubMed2005

Sensorimotor and cognitive slowing in schizophrenia as measured by the Symbol Digit Substitution Test.

OBJECTIVES: A vast amount of studies demonstrates the presence of psychomotor slowing in schizophrenia. The objective of the present study was to investigate whether this overall psychomotor slowing can be divided into distinct processes that differentially affect cognitive functioning in schizophrenia. METHODS: The pen-tip movements of 30 schizophrenic inpatients and 30 matched controls were digitally recorded during performance of the Symbol Digit Substitution Test (SDST) and analysed to differentiate matching time and writing time, representing the cognitive and sensorimotor component of slowing, respectively. In addition, the results were compared to each other and to the scores of traditional neuropsychological tests that assess domains such as memory and attention. RESULTS: Both matching time and writing time were longer in the schizophrenic patients relative to the controls but did not correlate. Only matching time correlated significantly with the conventional neuropsychological test results. CONCLUSIONS: Although schizophrenic patients display both sensorimotor and cognitive slowing, the two processes are unrelated. Furthermore, only the cognitive component was associated with most of the cognitive deficits as measured by traditional neuropsychological tests.

Adult↗
PubMed2004

Simple and complex movement-associated functional MRI changes in patients at presentation with clinically isolated syndromes suggestive of multiple sclerosis.

Using functional magnetic resonance imaging (fMRI), we investigated whether movement-associated functional changes of the brain are present in patients who are, most likely, at the earliest stage of multiple sclerosis (MS). Functional MRI exams were obtained from 16 patients at presentation with clinically isolated syndromes (CIS) suggestive of MS and 15 sex- and age-matched healthy volunteers during the performance of three simple and one more complex motor tasks with fully normal functioning extremities. fMRI analysis was performed using statistical parametric mapping (SPM99). Compared to healthy volunteers, CIS patients had increased activations of the contralateral primary sensorimotor cortex (SMC), secondary somatosensory cortex (SII), and inferior frontal gyrus (IFG), when performing a simple motor task with the dominant hand. The increased recruitment of the contralateral primary SMC was also found during the performance of the same motor task with the non-dominant hand and with the dominant foot. In this latter case, an anterior shift of the center of activation of this region was detected. During the performance of a complex motor task with the dominant upper and lower limbs, CIS patients had an increased recruitment of a widespread network (including the frontal lobe, the insula, the thalamus), usually considered to function in motor, sensory, and multimodal integration processing. The comparison of brain activations during the performance of simple vs. complex motor tasks showed that the movement-associated somatotopic organization of the cerebral and cerebellar cortices was retained in patients with CIS. Cortical reorganization occurs in patients at presentation with CIS highly suggestive of MS. Local synaptic reorganization, recruitment of parallel existing pathways, and reorganization of distant sites are all likely to contribute to the observed functional changes. Hum. Brain Mapping 21:106-115, 2004.

Adult↗
PubMed2005

Opposite effects of short- and long-duration isolation on ultrasonic vocalization, startle and prepulse inhibition in rats.

Housing conditions change the sensorimotor gating and the emotional state of rats. The prepulse inhibition (PPI) is a reduction in the startle reflex to loud sounds when they are preceded by acoustic stimuli of low-intensity, and this test has been considered to be a useful measurement of the functioning of sensory gating in animals and man. Rats reared under conditions of isolation from the time of weaning, but not for 1 week at adult age, display clear deficits in prepulse inhibition and in sensorimotor gating. Ultrasound vocalizations (USVs) at 20-24kHz are the usual defensive responses of rats exposed to threatening conditions such as novel situations. The amount of emissions of ultrasound vocalizations at these frequencies depends on whether the aversive stimuli are presented either alone or in combination. Given this background we evaluated the prepulse inhibition and the emission of ultrasound vocalizations in response to novelty in rats isolated for 1 day or 2 weeks and compared the results to those in grouped rats. We also examined whether the anxiolytic agent midazolam (0.5 and 1.0mg/kg) could reverse the effects of isolation under the experimental conditions used. Rats isolated for 1 day showed a significant increase in the number and duration of USVs together with an enhancement in the startle response to loud sounds, which were antagonized in a dose-dependent manner by midazolam. On the other hand, 2-week isolation had the effect of reducing the number of USVs emitted at 20-24kHz without changing the startle response. The PPI was not changed by isolation, irrespective of the duration of isolation (1 day or 2 weeks). The results suggest that 1 day and 2 weeks of isolation have opposite effects on the emotional state of the animals. While short periods of isolation cause an anxiolytic-sensitive enhancement of the defensive responses, longer periods tend to reduce the defensive reaction of the animals to aversive stimuli. Based on these results, this work presents a novel method for induction of two different modes of defensive response, which are proposed to be mediated by separate neural substrates in rats. Also, isolation from 1 day to 2 weeks has no effect on the expression of prepulse inhibition and, by extension, on the functioning of the sensory gating.

Adaptation, Physiological↗
PubMed1985

Noradrenergic modulation of sensorimotor processes in intact rats: the masseteric reflex as a model system.

The masseteric jaw closure reflex was utilized as a model system with which to gauge the functional activity of central noradrenergic neurons. This system was chosen because it is a simple monosynaptic reflex the neuronal substrate of which receives a dense noradrenergic input. The modulatory effects of norepinephrine (NE) on this response in the intact, chloral hydrate-anesthetized rat were studied with a variety of pharmacological strategies. Initially, a reflex facilitation was obtained with the catecholamine precursor L-DOPA. Manipulations with greater specificity of action on the noradrenergic system were then employed. First, we used the presynaptic alpha-2 noradrenergic agonist clonidine, which acts to decrease noradrenergic transmission. Clonidine attenuated the amplitude of the reflex, and this suppression was blocked by pretreatment with the alpha-2 antagonist yohimbine. The effects of yohimbine itself were then examined, and a biphasic effect was obtained. At low doses, at which it preferentially acts as an antagonist at presynaptic alpha-2 receptors and increases noradrenergic transmission, yohimbine enhanced the reflex. At higher doses, at which it also displays postsynaptic alpha-1 antagonist activity, yohimbine depressed the reflex. This reflex modulation by yohimbine was blocked by pretreatment with the alpha-1 antagonist prazosin. The anatomical site of the observed effect was then localized to the direct noradrenergic innervation of the reflex circuitry by locally destroying, with 6-hydroxydopamine, the noradrenergic terminals in the trigeminal motor nucleus mediating the response. This significantly attenuated the reflex modulation by yohimbine, without affecting elicitation of the reflex itself.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Computerized system for quantitative measurement of sensorimotor aspects of human performance.

The purpose of this article is to describe an integrated system for measuring selected aspects of human sensorimotor performance. The system consists of a computerized test battery, a database, and multiple software packages to present results for different applications. The system includes measures classified into major functional categories including sensation, range of motion, isometric muscle strength, anthropometric features, speed, reactions, muscle tone, coordination, body stability, and manual dexterity. A microcomputer is used to coordinate basic measurements obtained from a series of short-duration tests. Raw data are recorded in physical units (eg, degrees, milliseconds). A database currently consisting of over 2,000 data records of normal sensorimotor performance has been collected, permitting immediate comparison of patient data to a group of age- and sex-matched norms. This system permits an objective, reliable, and standardized method for measuring selected aspects of sensorimotor performance essential for physical therapists to quantify individual patient performance, document disability, justify reimbursement, screen employees and athletes, and demonstrate efficacy of treatment.

Activities of Daily Living↗
PubMed2004

Integrating sensory and motor mapping in a comprehensive MEG protocol: clinical validity and replicability.

Considerable evidence supports the idea of magnetoencephalography (MEG) being a valuable noninvasive tool for presurgical mapping of sensory and motor functions. In this study, we test the validity and replicability of a new experimental paradigm for simultaneous sensory and motor mapping using MEG recordings. This comprehensive sensorimotor protocol (CSSMP), where external mechanic stimulation serves as a cue for voluntary movements, allows the recording of sensory and motor cortical responses during a single activation task. The stability and replicability of MEG-derived recordings during this paradigm were tested in a group of eight neurologically normal volunteers and six patients with perirolandic lesions. We found that a common sensorimotor cortical network, engaging sensory (S1, S2) and motor (M1) areas, was reliably activated in all subjects and patients and that the results remained exceptionally stable over time. Additionally, the clinical validity of the MEG-derived maps of activation was tested through intraoperative electrocortical stimulation mapping in the group of patients. The MEG-derived anatomical maps for specific sensory (S1) and motor (M1) responses were verified, by direct cortical mapping, and confirmed with the patient's surgical outcome. The results of this validation study show that the so-called CSSMP is a reliable and reproducible method for assessing simultaneously sensory and motor areas. This method minimizes methodological problems and improves our knowledge of the spatiotemporal organization of the sensorimotor cortical network and helps to optimize the surgical management of patients with perirolandic lesions.

Adult↗
PubMedDate not supplied

[Intercentral reticulo-cortical relations of brain electrical activity during "animal hypnosis" in rabbits].

The electrical activity of the right and left sensorimotor and premotor cortical areas and right and left medulary reticular formation was recorded during "animal hypnosis" in rabbits. In this state, the spectral power of potentials (predominantly, in the delta-range) recorded from the left reticular formation was higher than that recorded from the right side. The value of the function of coherence between the right and left reticular recordings was decreased to 0.1-0.2 in the whole frequency range. The tight-side intrahemispheric coherence between the activities recorded from the sensorimotor cortex and reticular formation was higher than respective left-side values, whereas the coherent relations between the activities recorded from the reticular formation and premotor cortex were not changed (as compared to nonhypnotic state).

Animals↗
PubMed1996

Treatment of advanced Parkinson's disease by posterior GPi pallidotomy: 1-year results of a pilot study.

The effects of posterior internal pallidal ablation (GPi pallidotomy) on parkinsonian signs and symptoms were studied in 15 patients with medically intractable Parkinson's disease (PD). The sensorimotor territory of the internal portion of the globus pallidus and the adjacent optic tract and internal capsule were identified with microelectrode recording and stimulation. Radiofrequency lesions were then created in the identified sensorimotor territory. Pallidotomy significantly improved all cardinal parkinsonian motor signs (tremor, rigidity, akinesia/bradykinesia, and gait dysfunction) and reduced drug-induced motor fluctuations and dyskinesias. The improvements occurred predominately contralateral to the lesion, but were also present ipsilaterally. Early postoperative (3-month), mean total United Parkinson's Disease Rating Scale scores improved by 30.1% from preoperative values. Mean combined "on/off" Schwab and England Scale scores, a measure of functional independence, increased from 48.8% to 73.0% postoperatively. The mean total United Parkinson's Disease Rating Scale and Schwab and England scores did not show a statistically significant decline over the 1-year postoperative period. Surgery resulted in little morbidity, including a lack of significant deficits on neuropsychological and psychiatric testing. Physical and social functioning and vitality measures on the Medical Outcome Scale also showed significant improvement over the postoperative period. The findings of this pilot study demonstrate that ablation of the sensorimotor portion of the internal pallidum is a highly effective treatment for advanced PD, with benefits sustained at 1 year.

Adult↗
PubMed1995

Functional activation of the human ventrolateral frontal cortex during mnemonic retrieval of verbal information.

Regional cerebral blood flow was measured with positron emission tomography during the performance of a verbal free recall task, a verbal paired associate task, and tasks that required the production of verbal responses either by speaking or writing. Examination of the differences in regional cerebral blood flow between these conditions demonstrated that the left ventrolateral frontal cortical area 45 is involved in the recall of verbal information from long-term memory, in addition to its contribution to speech. The act of writing activated a network of areas involving posterior parietal cortex and sensorimotor areas but not ventrolateral frontal cortex.

Adult↗