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PubMed1998

Regionalized sensorimotor plasticity after hemispherectomy fMRI evaluation.

This study demonstrates the transfer of both motor and sensory functions from one hemisphere to the other in children who had an entire cortical hemisphere surgically removed. The areas of the cortex responsible for these new functions in the remaining hemisphere are associative motor and sensory areas and do not include the typical primary motor and somatosensory regions, thus suggesting the regionalization of brain plasticity. This regionalization can be evaluated with functional magnetic resonance imaging, supporting this technique as an effective tool in the study of brain plasticity.

Adolescent↗

PubMed1998

[Motor and cognitive functions of the basal ganglia].

Basal ganglia have been known as a motor center because their lesions cause motor disturbances in involuntary movements such as chorea, ballism or akinesia in Parkinsonism. The different types of involuntary movements are closely related to the underlying muscle tone. Mechanisms of bradykinesia or akinesia have been elaborated in physiological studies on Parkinson's disease, and the significance of sensorimotor processing or attention, arousal has been disclosed as a relevant factor of bradykinesia. Cognitive functions of the basal ganglia have attracted attention, particularly in the disorder of Parkinson's disease. Subcortical dementia, difficulty in formation or changes of concepts, is encountered in advanced stages of Parkinson's disease. Whether cognitive functions in the frontostriatal system are primarily related to the motor function of the brain is an issue for future study.

Basal Ganglia↗

PubMed1996

Functional magnetic resonance imaging in clinical neurology.

Functional magnetic resonance imaging is a relatively new, noninvasive technique which has a maximum spatial resolution in the range of 1 mm and temporal resolution of 0.1-1 s. The technique is not quantitative but results have proved reliable and reproducible and studies are quick to perform. Already substantial progress has been made in mapping the visual, sensorimotor and auditory systems and promising results achieved in the study of higher cognitive function such as memory and linguistic processing. Clinical applications have been made in epilepsy surgery, the study of schizophrenia, genetic abnormality and cerebral injury.

Brain↗

PubMed2004

Preoperative blood oxygen level-dependent functional magnetic resonance imaging in patients with primary brain tumors: clinical application and outcome.

OBJECTIVE: This study sought to evaluate the ability of blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to successfully identify functional cortical areas in patients with primary brain tumors, to evaluate the use of the fMRI results in presurgical planning, and to assess the functional outcome of the patients with respect to the functional maps obtained with fMRI. METHODS: The study included 25 consecutive preoperative fMRI sessions in patients with primary brain tumors in or near sensorimotor and/or language cortices. All fMRI paradigms were analyzed and rated according to the degree of success. Several distances between tumor and functional cortex as delineated with BOLD fMRI were measured to assess the topographic relationship between these two structures. Pre- and postoperative neurological statuses were obtained from the patients' journals. RESULTS: Acquisition of BOLD fMRI images was successful in 80% of the cases. The primary cause of unsuccessful fMRI was echo-planar imaging signal voids that were the result of previous craniotomy; the secondary cause was excessive motion. The neurosurgeons used the fMRI results for preoperative planning in 75% of the cases in which fMRI was successful. The risk of postoperative loss of function tested with fMRI was significantly lower when the distance between tumor periphery and BOLD activity was 10 mm or more. CONCLUSION: The majority of patients with primary brain tumors were capable of satisfactorily performing the fMRI paradigms, and the information obtained was used in the preoperative planning. A distance of 10 mm or more between the functional cortex, as delineated with fMRI, and the tumor significantly reduced the risk of postoperative loss of function.

Adult↗

PubMed1993

Functional mapping of the rat brain during drinking behavior: a fluorodeoxyglucose study.

Autoradiographic techniques using the radiolabeled glucose analog [14C]2-fluoro-2-deoxy-D-glucose (FDG) were used to map the functional activity in the CNS during drinking behavior. Rats were trained to drink water during a 1-h session each day. Half of the rats were injected with FDG and allowed to drink, while the other half were satiated prior to FDG injection. Uptake of FDG for drinking and control groups of rats was quantified in 60 brain structures from frontal cortex to cervical spinal cord. The largest percent increase in activity (96%) during drinking was in the lateral hypothalamus. Limbic structures with significant metabolic increases included the lateral septum (48%), lateral habenula (44%), and nucleus accumbens (32%). Thalamic nuclei activated included intralaminar (60%), zona incerta (51%), ventroposteromedial (50%), anterior ventral (47%), and dorsal medial (40%). Other structures with increases were the caudal caudate nucleus (53%) and the spinal trigeminal nucleus (45%). The findings were interpreted in light of related metabolic mapping studies of the effects of orofacial stimulation, dehydration, ingestion, arousal, and reward. It was concluded that this FDG study revealed primarily the involvement of structures linked to rewarding and arousal components of motivated drinking behavior, as well as sensorimotor correlates of the orofacial stimulation. The findings provide the first comprehensive functional map of brain systems related to drinking behavior in adult animals.

Animals↗

PubMed2000

The functional neuroanatomy of simple calculation and number repetition: A parametric PET activation study.

We examined cerebral activation patterns with positron emission tomography (PET) in 12 right-handed normal volunteers while they were completing simple calculation tasks or merely repeating numbers. Using a parametric experimental design, during calculation we found activation in the medial frontal/cingulate gyri, left dorsolateral prefrontal cortex, left anterior insular cortex and right anterior insular cortex/putamen, left lateral parietal cortex, and the medial thalamus. Number repetition engaged bilateral inferior sensorimotor cortex, bilateral temporal areas, and left inferior frontal cortex. These results suggest a functional anatomical network for simple calculation, which includes aspects of attention, auditory, and motor processing and the phonological store and articulatory loop components of working memory; they add some support for a special role of the parietal cortex in calculation tasks.

Adult↗

PubMed1994

Deviation in cerebral excitability: possible clinical implications.

Schizophrenia, a chemical signaling disorder in the brain, is also a deteriorating neurological disorder. The deficit in cerebral excitability, and associated reduced synaptic density, imply a risk of cortical breakdown of circuitry accompanied by an insufficient fill-in mechanism, and persistent silent spots, but no total loss of function, only dysfunction. This is subjectively experienced as deficiencies of cognition, perception and sensorimotor phenomena depending upon localization and connections of the disconnected circuitry. Considering the adversity inherent in this neural network, both the fast Hebbian pre-post form of learning and the slow pre-modulatory coincidence form of learning are probably impaired. The use of Feed Back Loops which usually govern our behaviour might also be impaired. In addition, we have to consider the daily problem of insufficient drive and motivation. Manic depressive psychosis, a chemical signaling disorder in the brain, is a true functional psychosis. The raised excitatory drive and raised synaptic density imply raised risk of uncoupling of circadian rhythms via the direct glutamatergic input to the suprachiasmatic nucleus of hypothalamus (SCN). This episodic brain stem dysfunction illustrates how a deficit in inhibition renders the brain unstable. The requirements of the fast Hebbian form of learning should easily be met, and neither should the slow forms of learning present a problem in networks characterized by excessive density.(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebral Cortex↗

PubMed2000

Functional rewiring of brain and spinal cord after injury: the three Rs of neural repair and neurological rehabilitation.

Gains in the use of the upper extremities and in walking after brain and spinal cord injury or stroke depend especially upon the effectiveness of spared sensorimotor nodes in the networks for motor control. Biological interventions for neural repair and motor recovery may involve strategies that replace cells or signalling molecules and stimulate the regrowth of axons. The greatest success of these interventions will depend upon the functional incorporation of spared and new cells and their processes into motor networks. The distributed and modular organization of the motor neurons of the cortex and spinal cord offer a substrate that arranges or represents particular patterns of movement, yet is highly adaptable to training. Neurological impairments and related disabilities can be reduced through rehabilitative retraining protocols that engage these critical components of the sensorimotor network to promote use-dependent adaptations and functional rewiring.

Animals↗

PubMed1994

Effects of estrogen treatment on sensorimotor task performance and brain dopamine concentrations in gonadectomized male and female CD-1 mice.

In Experiment I, castrated male and female CD-1 mice +/- estradiol benzoate (EB) treatment were tested for their performance on a skilled sensorimotor task consisting of walking across beams of varying widths (6, 9, 12, and 21 mm). To evaluate whether behavioral performance was related to nigrostriatal dopaminergic function, tissue dopamine concentrations were determined from the corpus striatum as well as the hypothalamus and olfactory tubercle. In general, sensorimotor performance improved for all treatment conditions as the beam width increased. Castrated male mice treated with oil vehicle showed the worst performance as indicated by significantly greater amounts of time to cross the beam. Treatment of castrated males with EB significantly improved their performance. Performance of the castrated females was not changed by EB treatment and was similar to that observed with the castrated + EB males. Significant gender differences in dopamine concentrations (female > male) were obtained in the corpus striatum, as well as the olfactory tubercle and hypothalamus. Dopamine levels were unaltered by EB treatment. In Experiment II, behavioral and neurochemical determinations were directly compared between castrated and intact male mice. Behavioral performance of castrates was significantly reduced compared to intact males. No differences in dopamine concentrations were obtained between these two groups; however, the hypothalamic dopamine/DOPAC ratio of castrates was significantly greater than that of intact male mice. These results demonstrate significant modulatory effects of EB in castrated male, but not female, mice upon sensorimotor performance and indicate that this task may provide an effective means to partial out modulatory effects of gonadal steroid hormones upon skilled sensorimotor performance. When the data of Experiments I and II are combined, it appears that the basis of this sensorimotor deficit in the males is the absence of gonadal steroid hormones. In addition, these results reveal significant gender differences in various dopaminergic systems in these mice.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2005

Gastric motor and sensory function.

PURPOSE OF REVIEW: Abnormalities of gastric sensory and motor function are considered key players in the pathogenesis of upper gastrointestinal symptoms in functional dyspepsia and in gastroparesis. This review summarizes recent progress in our understanding of normal and pathologic gastric sensory and motor function. RECENT FINDINGS: Several novel tests have been developed to study gastric sensitivity and meal-induced accommodation, including scintigraphic analysis of meal distribution within the stomach, single photon emission computed tomography of gastric volumes, and nutrient or water challenge tests. Several studies have reported on the occurrence of delayed gastric emptying in functional dyspepsia and in gastroparesis, but the correlation with symptoms was generally poor. The pathways and neurotransmitter involved in gastric hypersensitivity are progressively being unraveled. Several studies have confirmed and focused on increased symptom occurrence after nutrient challenge in functional dyspepsia. The role of the proximal stomach in the control of food intake and the stomach as a target in the treatment of obesity are areas of intense research. Studies have reported on pharmacologic approaches as well as electric stimulation in the treatment of gastric sensorimotor dysfunction. SUMMARY: Progress in our understanding of normal and abnormal gastric sensory and motor function may lead to new or improved treatment modalities. Areas of major advances are the study of meal-induced symptoms in functional dyspepsia, unraveling of the role of the stomach in the control of food intake, and the use of gastric electric stimulation in gastroparesis and in obesity.

Animals↗

PubMed1988

Increases in both cerebral glucose utilization and blood flow during execution of a somatosensory task.

To investigate local metabolic and hemodynamic interrelationships during functional activation of the brain, paired studies of local cerebral glucose utilization (lCMRGlc) and blood flow (lCBF) were carried out in 10 normal subjects (9 right-handed, 1 ambidextrous) at rest and during a unilateral discriminative somatosensory/motor task--palpation and sorting of mah-jongg tiles by engraved design. The extent of activation was assessed on the basis of percentage difference images following normalization to compensate for global shifts. The somatosensory stimulus elevated lCMRGlc by 16.9 +/- 3.5% (mean +/- standard deviation) and lCBF by 26.5 +/- 5.1% in the contralateral sensorimotor cortical focus; smaller increments were noted in the homologous ipsilateral site. The increments of lCMRGlc and lCBF correlated poorly with one another in individual subjects. Stimulation of the right hand resulted in significantly higher contralateral lCMRGlc activation (19.6%) than did stimulation of the left hand (14.1%) (p less than 0.005), whereas the lCBF response was independent of the hand stimulated. Our results indicate that both glycolytic metabolism and blood flow increase locally with the execution of an active sensorimotor task and suggest that both measures may serve as reliable markers of functional activation of the normal brain.

Adult↗

PubMed1992

Gender differences in correlations of cerebral glucose metabolic rates in young normal adults.

Correlational analysis of normalized regional cerebral metabolic data obtained by positron emission tomography, in healthy subjects in the 'resting' state (eyes covered, ears plugged) using [18F]2-fluoro-2-deoxy-D-glucose, demonstrated gender differences in patterns of functional associations. Fifteen women and 18 men (less than 40 yr) were scanned with a Scanditronix PC1024-7B tomograph. The brain was divided into 65 regions of interest (ROIs). There were no differences between men and women in global or regional metabolic rates, or in metabolic right-left asymmetries. Although the total number of significant correlations did not differ between men and women, patterns differed: female correlations rF were most positive than male correlations rM more often than rM greater than rF; and most rF greater than rM cases involved left frontal and sensorimotor ROIs, whereas most rM greater than rF cases involved right sensorimotor and occipital ROIs. The findings demonstrate gender differences in the pattern of functional neocortical interactions at the 'resting' state.

Adult↗

PubMed2002

Single-shot interleaved z-shim EPI with optimized compensation for signal losses due to susceptibility-induced field inhomogeneity at 3 T.

A new single-shot echo-planar imaging (EPI) sequence with interleaved z-shim and optimized compensation for susceptibility-induced signal loss is proposed in this paper. Experiments on human brain demonstrated that the new method is able to regain signal dropout in brain areas with severe susceptibility-induced local gradients, while its image acquisition speed is comparable to that of conventional single-shot EPI techniques. Significant signal-to-noise ratio improvements were demonstrated in the ventral prefrontal and lateral temporal lobes with the new technique compared to a conventional EPI. Brain activation experiments with a bilateral finger-tapping task were performed with intentionally introduced local gradients near the left sensorimotor cortex, by a small gadolinium (Gd)-doped bottle placed on the left side of the head. The results of the functional experiments showed that the interleaved z-shim EPI sequence effectively recovered the signal loss caused by the Gd-doped bottle and reliably detected activation signals in bilateral sensorimotor regions, while the activation signals on the left side diminished considerably in a conventional EPI technique. The new technique, with the capability of reducing susceptibility artifacts and rapid scanning speed, may be particularly useful for event-related functional MRI experiments in the base of the brain, which are of great importance in neuropsychiatric studies.

Adult↗

PubMed2005

Modulation of behavior and cortical motor activity in healthy subjects by a chronic administration of a serotonin enhancer.

UNLABELLED: SSRIs are postulated to modulate motor behavior. A single dose of selective serotoninergic reuptake inhibitors (SSRIs) like fluoxetine, paroxetine, or fluvoxamine, has been shown to improve motor performance and efficiency of information processing for simple sensorimotor tasks in healthy subjects. At a cortical level, a single dose of SSRI was shown to induce a hyperactivation of the primary sensorimotor cortex (S1M1) involved in the movement (Loubinoux, I., Boulanouar, K., Ranjeva, J. P., Carel, C., Berry, I., Rascol, O., Celsis, P., and Chollet, F., 1999. Cerebral functional magnetic resonance imaging activation modulated by a single dose of the monoamine neurotransmission enhancers fluoxetine and fenozolone during hand sensorimotor tasks. J. Cereb. Blood Flow Metab. 19 1365--1375, Loubinoux, I., Pariente, J., Boulanouar, K., Carel, C., Manelfe, C., Rascol, O., Celsis, P., and Chollet, F., 2002. A Single Dose of Serotonin Neurotransmission Agonist Paroxetine Enhances Motor Output. A double-blind, placebo-controlled, fMRI study in healthy subjects. NeuroImage 15 26--36). Since SSRIs are usually given for several weeks, we assessed the behavioral and cerebral effects of a one-month chronic administration of paroxetine on a larger group. In a double-blind, placebo controlled and crossover study, 19 subjects received daily 20 mg paroxetine or placebo, respectively, over a period of 30 days separated by a wash-out period of 3 months. After each period, the subjects underwent an fMRI (active or passive movement, dexterity task, sensory discrimination task) and a behavioral evaluation. Concurrently, a TMS (transcranial magnetic stimulation) study was conducted (Gerdelat-Mas, A., Loubinoux, I., Tombari, D., Rascol, O., Chollet, F., Simonetta-Moreau, M., 2005. Chronic administration of selective serotonin re-uptake inhibitor (SSRI) paroxetine modulates human motor cortex excitability in healthy subjects. NeuroImage 27,314--322). RESULTS: On the one hand, paroxetine improved motor performances at the finger tapping test (P=0.02) without affecting choice reaction time, strength and dexterity significantly. Subjects were also faster in processing the spatial incongruency between a stimulus and the motor response (P=0.04). In order to differentiate behavioral components, a principal component analysis was performed on all motor tests, and several characteristics were differentiated: strength, speed, skill, attention, and motor response coding. Paroxetine would improve the efficiency of motor response coding (MANOVA on the factors; factor 3, P=0.01). On the other hand, the chronic administration induced a significant hypoactivation of S1M1 whatever the task: motor or sensory, simple or complex (random effect analysis, P<0.05). The hypoactivation correlated with the improvement of performances at the finger tapping test (P<0.05) suggesting more efficiency in cerebral motor processing. CONCLUSIONS: Our results showed a clear modulation of sensory and motor cerebral activation after a chronic paroxetine administration. An improvement in both behavior and cerebral efficiency was suggested. It could be hypothesized that monoamines, by an unspecific effect, may tune the response of pyramidal neurons to optimize performances.

Adult↗

PubMed2004

Optimality principles in sensorimotor control.

The sensorimotor system is a product of evolution, development, learning and adaptation-which work on different time scales to improve behavioral performance. Consequently, many theories of motor function are based on 'optimal performance': they quantify task goals as cost functions, and apply the sophisticated tools of optimal control theory to obtain detailed behavioral predictions. The resulting models, although not without limitations, have explained more empirical phenomena than any other class. Traditional emphasis has been on optimizing desired movement trajectories while ignoring sensory feedback. Recent work has redefined optimality in terms of feedback control laws, and focused on the mechanisms that generate behavior online. This approach has allowed researchers to fit previously unrelated concepts and observations into what may become a unified theoretical framework for interpreting motor function. At the heart of the framework is the relationship between high-level goals, and the real-time sensorimotor control strategies most suitable for accomplishing those goals.

Adaptation, Physiological↗

PubMed1993

The cerebellum as a predictor of neural messages--I. The stable estimator hypothesis.

To describe how the central nervous system combines sensory messages, the hypothesis of a "stable estimator" is proposed: the central nervous system would construct internal estimates of the physical variables characterizing the body movements (e.g. head rotational velocity in space), while a regulating circuit would optimize the process of estimation of each variable, according to the available information and the overall performances of the sensorimotor reactions. The stable estimator of each variable would be embedded in a definite folium of the cerebellar cortex and the related cerebellar and brainstem nuclei. It would be controlled by the related part of the inferior olive. The estimate of each physical variable would be constructed by complementing the message from a dedicated sensory system (e.g. the semi-circular canals, which measure head rotational velocity in space) by neural messages related to the same variable (e.g. eye velocity in the head and retinal slip). Thus, the estimate would be accurate over the widest possible physiological ranges of frequency and velocity. The complementing signals would result from combining estimates of other variables (such as gaze velocity and eye velocity in the orbit), according to rules reproducing the relationships between physical variables. From the same complementing signals, the message from the dedicated sensory system would be predicted, and it is argued that this predictive function resides in the cerebellar cortex. The inferior olive would compare an actual signal about the performance of a sensorimotor reaction to signals of expected performance, computed from the various internal estimates of the variables which determine this performance. Any erroneous setting in a stable estimator would cause differences between the actual and the expected values. Then the inferior olive would compute an error signal directing compensatory functional plasticity. Finally, the whole estimating circuit would be regulated so that the internal coherence between neural messages and the performance of sensorimotor reactions would be achieved. Anatomical identifications and rules of functional plasticity are proposed.

Adaptation, Psychological↗

PubMed2002

Nigral and pallidal inputs to functionally segregated thalamostriatal neurons in the centromedian/parafascicular intralaminar nuclear complex in monkey.

In primates, thalamostriatal projections from the centromedian (CM) and parafascicular (Pf) nuclei are strong and organized according to a strict pattern of functional connectivity with various regions of the striatal complex. In turn, the CM/Pf complex receives a substantial innervation from the internal globus pallidus (GPi). In this study, we demonstrate that the substantia nigra pars reticulata (SNr) also provides a massive input to Pf in monkeys. These pallidothalamic and nigrothalamic projections provide routes whereby information can flow in functional loops between the basal ganglia and the intralaminar nuclear group. To understand better the anatomical organization and the degree of functional specificity of these loops, we combined retrograde and anterograde labeling methods from functionally defined regions of the striatum and GPi/SNr to determine the relationships between thalamostriatal neurons and basal ganglia afferents. Together with previous studies, our data suggest the existence of tightly connected functional circuits between the basal ganglia and the CM/Pf in primates: 1) A "sensorimotor" circuit links together the medial two-thirds of CM, the postcommissural putamen, and the ventrolateral part of the caudal GPi; 2) a "limbic" circuit involves the rostral one-third of Pf, the ventral striatum, and the rostromedial pole of GPi; and 3) an "associative"circuit exists between the caudal two-thirds of Pf, the caudate nucleus, and the SNr. An additional "associative" circuit that involves the caudate-receiving territory of GPi (dorsal one-third), the dorsolateral Pf (Pfdl), and the precommissural putamen was also disclosed. In conclusion, findings of this study provide additional evidence for the high degree of functional specificity of the thalamostriatal system through which CM/Pf may provide attention-specific sensory information important for conditional responses to the primate striatum.

Animals↗

PubMed2002

Integration of sulcal and functional information for multimodal neuronavigation.

OBJECT: The authors present the use of cortical sulci, segmented from magnetic resonance (MR) imaging, and functional data from functional (f)MR imaging and magnetoencephalography (MEG) in the image-guided surgical management of lesions adjacent to the sensorimotor cortex. METHODS: In an initial set of 11 patients, sulci near lesions were automatically segmented from MR imaging data sets, then MEG and fMR imaging examinations were performed. Relevant functional information was preoperatively interpreted and selected from MEG and fMR imaging and subsequently transferred to the navigation system for selected sulci. A neuronavigation system consisting of a surgical microscope with enhanced reality overlay display was used. Data were displayed as contours on the cut-plane images of a stereotactic workstation and as contours on the overlay screen of the head-up display within the optical path of the right eyepiece of the surgical microscope. CONCLUSIONS: This method, in which both sulcal and functional mapping are used for surgery planning and neuronavigation, provides helpful information. It is a promising procedure for the treatment of patients who harbor lesions in areas around the eloquent cortex.

Adult↗