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PubMedDate not supplied

[The significance of multiple neuromediator activity in supporting integrative brain functions].

Properties were studied of reactions of neural cells of the sensorimotor cortical area to locally microionophoretically administered l-glutamate, acetylcholine, norepinephrine and gamma-aminobutyric acid. It is shown that neuronal reactions to the action of the above-mentioned transmitters differ both in direction of change in the impulse activity frequency and in temporal offracteristics (latency and duration of after-effect). It is substantiated that due to the specificity of temporal ranges of action of the transmitter on neural cells, the possibility of effective interaction and temporal coding of heterofunctional information is provided.

Acetylcholine↗

PubMed2000

Increasing CNS norepinephrine levels by the precursor L-DOPS facilitates beam-walking recovery after sensorimotor cortex ablation in rats.

The present investigation was conducted to document a role of L-threo-3,4-dihydroxyphenylserine (L-DOPS), precursor of L-norepinephrine (NE), in the functional recovery from beam-walking performance deficits in rats after unilateral sensorimotor cortex ablation. L-DOPS was administered simultaneously with benserazide (BSZ; a peripheral aromatic amino acid decarboxylase inhibitor), and the regional contents of NE in the cerebral cortex, hippocampus, and cerebellum were assayed. Behavioral recovery was demonstrated by the rats treated with L-DOPS and BSZ, and the rate of recovery was significantly different from that of either BSZ-treated or vehicle-treated control rats. The NE tissue levels in the three discrete regions of the rat brain were significantly elevated in the experimental rats receiving both L-DOPS and BSZ. The present studies indicate that increasing NE levels by the precursor L-DOPS may be responsible for facilitating behavioral recovery from beam-walking performance deficits in rats, and further suggest that L-DOPS may become one of the candidate compounds for further clinical human trials promoting functional recovery after injuries to the cerebral cortex.

Animals↗

PubMed2001

The cortical connections of area V6: an occipito-parietal network processing visual information.

The aim of this work was to study the cortical connections of area V6 by injecting neuronal tracers into different retinotopic representations of this area. To this purpose, we first functionally recognized V6 by recording from neurons of the parieto-occipital cortex in awake macaque monkeys. Penetrations with recording syringes were performed in the behaving animals in order to inject tracers exactly at the recording sites. The tracers were injected into the central or peripheral field representation of V6 in different hemispheres. Irrespective of whether injections were made in the centre or periphery, area V6 showed reciprocal connections with areas V1, V2, V3, V3A, V4T, the middle temporal area /V5 (MT/V5), the medial superior temporal area (MST), the medial intraparietal area (MIP), the ventral intraparietal area (VIP), the ventral part of the lateral intraparietal area and the ventral part of area V6A (V6AV). No labelled cells or terminals were found in the inferior temporal, mesial and frontal cortices. The connections of V6 with V1, and with all the retinotopically organized prestriate areas, were organized retinotopically. The connection of V6 with MIP suggests a visuotopic organization for this latter. Labelling in V6A and VIP after either central or peripheral V6 injections was very similar in location and extent, as expected on the basis of the nonretinotopic organization of these areas. We suggest that V6 plays a pivotal role in the dorsal visual stream, by distributing the visual information coming from the occipital lobe to the sensorimotor areas of the parietal cortex. Given the functional characteristics of the cells of this network, we suggest that it could perform the fast form and motion analyses needed for the visual guiding of arm movements as well as their coordination with the eyes and the head.

Animals↗

PubMed1996

The interactive use of magnetoencephalography in stereotactic image-guided neurosurgery.

OBJECTIVE: To expand the use of magnetoencephalography (MEG) functional mapping in the operating room as well as preoperatively, a method of integrating the MEG sensorimotor mapping information into a stereotactic database, using computed tomographic scans, magnetic resonance imaging scans, and digital angiography, was developed. The combination of functional mapping and the stereotactic technique allows simultaneous viewing of the spatial relationship between the MEG-derived functional mapping, the radiological/structural anatomic characteristics, and the pathological abnormality. METHODS: MEG data were collected using a MAGNES II Biomagnetometer and were incorporated into the COMPASS frame-based and REGULUS frameless stereotactic systems. The transformation process, by calculating a translational vector and a rotation matrix, integrates functional and anatomic information that is then directly available intraoperatively in the stereotactic database. This procedure was employed in 10 patients undergoing computer-assisted stereotactic volumetric resections for lesions involving the sensorimotor cortex. The principles of coregistration and coordinate transformation are reviewed in the context of preoperative functional mapping. We introduce innovations to apply these techniques to intraoperative stereotactic systems. RESULTS: Tests of the accuracy of the intraoperative integration of functional information in patients and calibration phantoms indicated close agreement with earlier preoperative methods. The intraoperative availability of functional information was a significant aid to the surgeon because it provided more accurate information on the location of functional tissue than could be derived solely by radiological criteria. CONCLUSION: The real-time availability of functional mapping information in an interactive fashion can reduce surgical risk and minimize functional morbidity. Within the ever-expanding realm of functional mapping and image-guided neurosurgery, further progress and integration of these methods is critical for resection of lesions involving eloquent cortex.

Adult↗

PubMed1983

Considerations for functional training in adults after head injury.

Functional deficits in head-injured patients are a major concern to physical therapists involved in the rehabilitation process. Functional outcomes are affected by deficits in behavior, cognition, communication, and sensorimotor abilities. These deficits interact frequently and must be considered in planning and implementing treatment. The purpose of this paper is to describe the deficits affecting functional abilities, to discuss the rationale for functional assessment, and to provide treatment suggestions for functional retraining. The suggestions include retraining of protective and equilibrium responses and advanced locomotor skills and use of assistive devices or orthoses. Problems are identified in functional outcome reporting methods. Research endeavors are addressed for physical management during the recovery process and its relationship to functional outcomes.

Adult↗

PubMed2005

The spatiotemporal pattern of auditory cortical responses during verbal hallucinations.

Functional magnetic resonance imaging (fMRI) studies can provide insight into the neural correlates of hallucinations. Commonly, such studies require self-reports about the timing of the hallucination events. While many studies have found activity in higher-order sensory cortical areas, only a few have demonstrated activity of the primary auditory cortex during auditory verbal hallucinations. In this case, using self-reports as a model of brain activity may not be sensitive enough to capture all neurophysiological signals related to hallucinations. We used spatial independent component analysis (sICA) to extract the activity patterns associated with auditory verbal hallucinations in six schizophrenia patients. SICA decomposes the functional data set into a set of spatial maps without the use of any input function. The resulting activity patterns from auditory and sensorimotor components were further analyzed in a single-subject fashion using a visualization tool that allows for easy inspection of the variability of regional brain responses. We found bilateral auditory cortex activity, including Heschl's gyrus, during hallucinations of one patient, and unilateral auditory cortex activity in two more patients. The associated time courses showed a large variability in the shape, amplitude, and time of onset relative to the self-reports. However, the average of the time courses during hallucinations showed a clear association with this clinical phenomenon. We suggest that detection of this activity may be facilitated by examining hallucination epochs of sufficient length, in combination with a data-driven approach.

Acoustic Stimulation↗

PubMed1976

Functional representation on the medial aspect of the frontal lobes in man.

Sensorimotor responses to stimulation of the medical frontal and cingulate area were studied in seven unrestrained, unsedated patients who suffered from intractable seizures. Complex postural synergies involving the trunk and proximal extremities appeared contralaterally or occasionally bilaterally. Contraversive turning of head and eyes was not observed. Sensory responses from the supplementary motor area were referred contralaterally and focally; those from the cingulate gyrus were widely referred. Speech impairment from stimulation of the supplementary motor area showed striking similarities with that obtained from stimulation in the frontostriatal region or lateral aspect of the frontal lobe. The observations support the hypothesis that interference with striatal function may be the basis of speech inhibition produced by stimulation of the frontal lobe.

Brain Mapping↗

PubMed2005

The functional neuroanatomy of coordinated orofacial movements: sparse sampling fMRI of whistling.

Whistling serves as a model for a skilful coordinated orofacial movement with sensorimotor integration of auditory and proprioceptive input. The neural substrate of whistling was investigated by sparse sampling functional MRI (fMRI) where the motor task occurred during a silent interval between successive image acquisitions to minimize task-related imaging artefacts. Whistling recruited a symmetrically represented neural network including primary motor and ventral premotor cortex (PMv), SMA, cingulate gyrus, basal ganglia, primary and secondary somatosensory cortex, amygdala, thalamus and cerebellum. A temporal analysis revealed higher activity of left sensory cortex, right PMv and cerebellum during late execution compared to initiation of whistling. Task-related signal changes in right PMv and right paravermal cerebellum were found to correlate with the amplitude of the whistle sound in a separate correlation analysis. The findings emphasize the role of ventral premotor cortex, cerebellum and somatosensory areas as integrators of afferent input within a distributed orofacial sensorimotor network.

Adult↗

PubMed2001

Effect of focal and nonfocal cerebral lesions on functional connectivity studied with MR imaging.

BACKGROUND AND PURPOSE: Functional connectivity MR (fcMR) imaging is used to map regions of brain with synchronous, regional, slow fluctuations in cerebral blood flow. We tested the hypothesis that focal cerebral lesions do not eradicate expected functional connectivity. METHODS: Functional MR (fMR) and fcMR maps were acquired for 12 patients with focal cerebral tumors, cysts, arteriovenous malformations, or in one case, agenesis of the corpus callosum. Task activation secondary to text listening, finger tapping, and word generation was mapped by use of fMR imaging. Functional connectivity was measured by selecting "seed" voxels in brain regions showing activation (based on the fMR data) and cross correlating with every other voxel (based on data acquired while the subject performed no task). Concurrence of the fMR and fcMR maps was measured by comparing the location and number of voxels selected by both methods. RESULTS: Technically adequate fMR and fcMR maps were obtained for all patients. In patients with focal lesions, the fMR and fcMR maps correlated closely. The fcMR map generated for the patient with agenesis of the corpus callosum failed to reveal functional connectivity between blood flow in the left and right sensorimotor cortices and in the frontal lobe language regions. Nonetheless, synchrony between blood flow in the auditory cortices was preserved. On average, there was 40% concurrence between all fMR and fcMR maps. CONCLUSION: Patterns of functional connectivity remain intact in patients with focal cerebral lesions. Disruption of major neuronal networks, such as agenesis of the corpus callosum, may diminish the normal functional connectivity patterns. Therefore, functional connectivity in such patients cannot be fully demonstrated with fcMR imaging.

Agenesis of Corpus Callosum↗

PubMed2005

Fatigue induced by intermittent maximal voluntary contractions is associated with significant losses in muscle output but limited reductions in functional MRI-measured brain activation level.

The main purpose of this study was to characterize brain activation patterns during a fatigue task involving repetitive maximal voluntary contractions (MVC) of finger flexor muscles. Fourteen young, healthy human participants performed approximately 100 handgrip MVCs (each 2-s contraction was followed by a 1-s rest) while their brain was imaged by functional MRI (fMRI). The handgrip force and electromyograms (EMG) of the finger flexors declined progressively to about 40% of the initial values at the end of the fatigue task, suggesting that significant muscle fatigue had occurred. In contrast, the level of the fMRI signal in the primary (sensorimotor), secondary (supplementary motor), and association (prefrontal and cingulate) motor-function cortices did not change significantly throughout the fatigue task (although the signal of the primary sensorimotor cortex showed a clear trend of decline). The fMRI data from the task of intermittent handgrip MVCs differed dramatically from those obtained in a 2-min sustained handgrip MVC published in a recent report, in which the overall fMRI-measured brain activation level was substantially lower and followed an increase-then-decrease pattern compared to the linear decreases in force and EMG. These results support the notion that the motor cortical centers control the tasks of repetitive and continuous muscle contractions differently and that there is a decoupling in the signal changes of the brain and muscles during muscle fatigue processes induced by maximal voluntary contractions.

Electromyography↗

PubMed2004

Brain mechanisms for preparing increasingly complex sensory to motor transformations.

Movements made in response to sensory cues require the brain to transform sensory information into an appropriate motor output. Sensorimotor mappings used in daily life range from direct or "standard" to highly complex. In "nonstandard" sensorimotor tasks, the visual stimulus guiding an action is often not the target of the action. A common example of such a nonstandard mapping is the use of a computer mouse on a horizontal surface to guide an object visible on a vertical monitor. The present study used event-related BOLD fMRI to examine how patterns of brain activity vary as sensorimotor mappings become progressively more complicated. We observed significantly different patterns of cortical activity depending on the level of dissociation between a sensory input and a required motor response. Our results suggest the presence of a functional network generally involved in performing the type of nonstandard sensorimotor tasks examined. This putative network includes regions of the primary motor cortex, medial motor areas, the superior parietal lobule (SPL), and the lateral premotor cortex. The extent of activity in active areas varied depending on the characteristics of the particular sensorimotor mapping used in performing a task. Furthermore, in addition to this putative network, specific task-related areas of activity were observed.

Adult↗

PubMed2000

Repetitive peripheral magnetic stimulation alleviates tactile extinction.

Despite its frequency in right brain damaged patients crucial mechanisms of tactile extinction are still obscure and treatments are unavailable. Recent PET observations suggest a hypometabolism in the primary and secondary somatosensory cortex of the lesioned hemisphere in patients with tactile extinction. Functional and morphological investigations have shown that the sensorimotor cortex has a remarkable capability of reorganization when the sensory inflow is changed. Repetitive peripheral magnetic stimulation (RPMS) applied in patients suffering from central paresis alleviates sensorimotor as well as cognitive deficits by the induction of proprioceptive inflow, thereby activating plasticity in the CNS. Based on the observation of reduced metabolic activity in patients suffering from tactile extinction we applied RPMS to explore the effects of peripheral sensory stimulation on tactile extinction. Fourteen right-hemisphere lesioned patients with tactile extinction were randomly allocated to an experimental and a control group. The experimental group received one single RPMS treatment of the left forearm as well as a condition of attentional cueing known to improve visual extinction. The control group, with comparable tactile extinction scores, neither received RPMS nor verbal cueing, but was tested twice to evaluate possible learning or test repetition effects. In the experimental group RPMS led to a significant reduction of left-sided extinctions in the recognition of different tactual surfaces, but had no effect on ipsilesional errors. In contrast, attentional cueing had no significant effect on left-sided extinction errors but unexpectedly increased right-hand extinction errors slightly but significantly. The control group showed stable extinction scores of the left- and right-hand stimulus across two measurements, thus ruling out learning or test repetition effects. These results show that sensory inflow is an important modulatory factor in tactile extinction. Furthermore, multiple RPMS may prove a promising way for the rehabilitation of patients with this disorder.

Adult↗

PubMed1980

Language comprehension in sensorimotor stages V and VI.

A cross-sectional study of language comprehension in relation to cognitive functioning in 48 to 10-to-21 month old children, 4 at each month of age, revealed significant correlations between comprehension and five sensorimotor subscales. Age, however, was the only significant predictor in multiple regression analyses adding either age or sensorimotor subscale in second. In specific instances in which sensorimotor tasks tapped hypothetical prerequisites to specific language comprehension items, the two domains corresponded closely; but the cognitive domain was not always the first to be passed. Comprehension items were ordered from easy to hard as follows: 1) understanding single words for present people or objects; 2) for actions; 3) for absent people or objects; 4) understanding two words for the semantic relations possessor-posession, action-object, and agent-action; 5) understanding three words for agent-action-object. Implications for the Cognition Hypothesis are discussed.

Age Factors↗

PubMed2006

Eye movement and visual search: are there elementary abnormalities in autism?

Although atypical eye gaze is commonly observed in autism, little is known about underlying oculomotor abnormalities. Our review of visual search and oculomotor systems in the healthy brain suggests that relevant networks may be partially impaired in autism, given regional abnormalities known from neuroimaging. However, direct oculomotor evidence for autism remains limited. This gap is critical since oculomotor abnormalities might play a causal role in functions known to be impaired in autism, such as imitation and joint attention. We integrate our oculomotor review into a developmental approach to language impairment related to nonverbal prerequisites. Oculomotor abnormalities may play a role as a sensorimotor defect at the root of impairments in later developing functional systems, ultimately resulting in sociocommunicative deficits.

Attention↗

PubMed2000

A PET study of visuomotor learning under optical rotation.

We measured the regional cerebral blood flow (rCBF) in six healthy volunteers with PET (positron emission tomography) and H(15)(2)O to identify the areas of the human brain involved in sensorimotor learning. The learning task was visually guided reaching with sensorimotor discrepancy caused by optical rotation. PET measurements were performed in the early and late stages of the adaptation to the sensorimotor perturbation. Control measurements were obtained during an eye movement task and a reaching task without optical rotation. The rCBF data of each learning stage were compared to those of both control conditions. During the early stage, rCBF increases were detected in the rostral premotor cortex bilaterally, the posterior part of the left superior parietal lobule (SPL), and the right SPL including the intraparietal sulcus (IPS). During the late stage, rCBF increases were detected in the left caudal premotor area, the left supplementary motor area proper, the left SPL, the right SPL including the IPS, and the right postcentral sulcus extending to the inferior parietal lobule. These results reveal that sensorimotor learning accompanies changes in the recruited cortical areas during different stages of the adaptation, reflecting the different functional roles of each area for different components of adaptation, from learning of new sensorimotor coordination to retention or retrieval of acquired coordination.

Adult↗

PubMed2001

Theta band oscillation and synchrony in the hippocampal formation and associated structures: the case for its role in sensorimotor integration.

The current review advances the argument that it is naïve to ascribe a unitary function to the hippocampal formation (HPC). Rather, it is more productive to consider the hippocampal formation as consisting of a number of subsystems, each subsystem defined by its own particular neural circuitry. Among examples of neural circuitry appearing in current hippocampal literature are theta, beta and gamma oscillations, sharp waves, place cells and head orientation cells. Data are reviewed supporting the case that theta band oscillation and synchrony is involved in mechanisms underlying sensorimotor integration. Specifically, the neural circuitry underlying the production of oscillation and synchrony (theta) in limbic cortex and associated structures function in the capacity of providing voluntary motor systems with continually updated feedback on their performance relative to changing environmental (sensory) conditions. A crucial aspect of this performance is the intensity with which the motor programs are initiated and maintained. The ascending brainstem HPC synchronizing pathways make the primary contribution in this regard. These pathways originate in the rostral pontine region, ascend and synapse with caudal diencephalic nuclei, which in turn send projections to the medial septal region. The medial septum functions as the node in the ascending pathways, sending both cholinergic and GABA-ergic projections to the HPC. An updated version of the sensorimotor integration model including anatomical details is presented and discussed.

Brain Stem↗

PubMed1990

Input-output relationships in the jaw and orofacial motor zones of the cat cerebral cortex.

Input-output relationships of the jaw and orofacial motor zones in the cerebral cortex of lightly anesthetized cats were studied. These relationships were examined by studying the motor effects produced by intracortical microstimulation (ICMS) and recording from single neuron. Jaw and orofacial motor effects were evoked by ICMS of the anterior part of the coronal and lateral sigmoid gyri (C-S motor zone) and the lateral wall of the presylvian sulcus (P motor zone). ICMS of the P motor zone produced more complex movements than that of the C-S motor zone. Repetitive stimulation of the P motor zone also evoked rhythmic jaw movements. Almost all cortical cells located in the C-S motor zone responded to tactile stimulation of cutaneous skin of the orofacial regions or the tooth, whereas those of the P motor zone received no cutaneous input from the orofacial regions. Cytoarchitectonically, the C-S motor zone was restricted to areas 3a, 6a beta and occasionally to area 4 gamma, whereas the P motor zone was represented to area 6a beta. Therefore, it is concluded that the C-S motor zone might be involved in sensorimotor integration of the jaw and orofacial motor functions, whereas the P motor zone might function only as a command area for jaw and orofacial movements.

Animals↗

PubMed1996

Sensorimotor impairments in Wistar Kyoto rats with cerebral infarction, induced by unilateral occlusion of the middle cerebral artery: recovery of function.

Wistar Kyoto (WKY) rats with cerebral infarction induced by permanent unilateral occlusion of the middle cerebral artery (MCA) and sham-operated rats were tested in a series of simple behavioral test 2, 16 and 37 days after surgery. In addition, the motility of the animals was measured over a period of 62 h, after the third test series. A subset of the tests appeared to be suitable to assess the effects of cerebral infarction, namely, grasping reflex of contralateral hindpaw, circling behavior, forelimb flexion, hindlimb flexion, and latency to fall off a square bridge. Except for the impaired grasping reflex of the contralateral hindpaw, there was spontaneous complete recovery of function by the third test session, 37 days after surgery. Some of the other tests might not have been sensitive enough to detect the effects of the unilateral MCA-occlusion (MCA-O) on behavior. Moreover, the WKY rats were very inactive in some of the tests, so that reliable scoring of the effects was not always possible. A rat strain other than the WKY strain might be more suitable to study the behavioral consequences of MCA-O.

Animals↗