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At least 541 records · Page 30Linked to original sources
PubMed1997

"Willed action": a functional MRI study of the human prefrontal cortex during a sensorimotor task.

Functional MRI (fMRI) was used to examine human brain activity within the dorsolateral prefrontal cortex during a sensorimotor task that had been proposed to require selection between several responses, a cognitive concept termed "willed action" in a positron emission tomography (PET) study by Frith et al. [Frith, C. D., Friston, K., Liddle, P. F. & Frackowiak, R. S. J. (1991) Proc. R. Soc. London Ser. B 244, 241-246]. We repeated their sensorimotor task, in which the subject chooses to move either of two fingers after a stimulus, by fMRI experiments in a 2.1-T imaging spectrometer. Echo-planar images were acquired from four coronal slices in the prefrontal cortex from nine healthy subjects. Slices were 5 mm thick, centers separated by 7 mm, with nominal in-plane spatial resolution of 9.6 x 5.0 mm2 for mean data. Our mean results are in agreement with the PET results in that we saw similar bilateral activations. The present results are compared with our previously published fMRI study of a verbal fluency task, which had also been proposed by Frith et al. to elicit a "willed action" response. We find a clear separation of activation foci in the left dorsolateral prefrontal cortex for the sensorimotor (Brodmann area 46) and verbal fluency (Brodmann area 45) tasks. Hence, assigning a particular activated region to "willed action" is not supported by the fMRI data when examined closely because identical regions are not activated with different modalities. Similar modality linked activations can be observed in the original PET study but the greater resolution of the fMRI data makes the modality linkages more definite.

Female↗
PubMed1998

A parametric analysis of the 'rate effect' in the sensorimotor cortex: a functional magnetic resonance imaging analysis in human subjects.

We studied the effects of different movement speeds of unimanual right hand movements on functional magnetic resonance signal changes in the sensorimotor cortex using echo planar imaging (EPI). Six healthy right-handed subjects were scanned at rest and while executing a finger tapping task with their right index finger. Movement frequency was visually paced at rates ranging from 0.5 to 5 Hz, separated by 0.5 Hz steps. The blood oxygen level dependent (BOLD) response within the left sensorimotor cortex was linearly and positively related to movement frequency. However, this relation holds (r2 = 0.91) only for movement frequencies faster than 1 Hz (1.5-5 Hz). For the slower frequencies there was an initial sharp increase of the BOLD response from 0.5 to 1 Hz followed by an activity drop for 1.5 Hz. These results are compatible with the idea that two different motor control modes are operative during slow or fast movements. During slow movements a computational demanding on-line feedback control mode is operative resulting in strong BOLD signals indicating extensive neural activity. During faster movements on the other hand a program-like motor control mode is operative resulting in less demanding neural computations. The amount of neural computation for the latter control mode increases with increasing movement speed.

Adult↗
PubMed2002

Interhemispheric reorganization of motor hand function to the primary motor cortex predicted with functional magnetic resonance imaging and transcranial magnetic stimulation.

The objective of this study was presurgical assessment of reorganization of motor hand function in an 11-year-old girl with intractable epilepsy and a right-sided hemiplegia resulting from an extensive perinatal left hemispheric stroke. Prior to a left functional hemispherectomy, functional magnetic resonance imaging (MRI) showed that both nonparetic and paretic motor hand function predominantly activated the right primary motor cortex, whereas no activation was found in the left hemisphere. Transcranial magnetic stimulation of the right central area yielded responses in both the nonparetic and the paretic hand, whereas no responses were obtained after stimulation of the affected hemisphere. Both techniques indicated that motor function was mediated by corticospinal fibers originating from the undamaged (primary) motor cortex and predicted no further loss of motor hand function after surgery. Indeed, subsequent functional hemispherectomy induced no new sensorimotor deficits. Functional MRI was repeated 22 months after surgery and matched preoperative sensorimotor functional MRI findings, confirming reorganization of the primary motor cortex. No additional reorganization was introduced by surgery.

Brain Infarction↗
PubMed1996

Presurgical identification of the primary sensorimotor cortex by functional magnetic resonance imaging.

The ability of functional magnetic resonance (MR) imaging to detect a selective sensorimotor cortex activation in healthy subjects and the feasibility of motor activation in patients with lesions around the central sulcus were investigated. Twenty-five healthy volunteers performed 100 motor activation trials, using a variety of motor tasks, which were monitored by several image analysis methods. The functional images were obtained using a 1.5-tesla standard MR imaging system magnet with blood oxygenation level-dependent contrast. Four patients were assessed using functional MR imaging and invasive cortical mapping. Rolandic cortex activation was observed in 98% of the trials performed on healthy subjects in which no head motion occurred. Nevertheless, the cortical response was not selective in a task-rest analysis due to concurrent activation of neighboring regions. Across-task comparison analyses were useful in cancelling nonrelevant activity in most cases (86%). In the patient group, the region identified as the sensorimotor cortex by invasive means corresponded accurately to the area that was activated in functional MR imaging. Present data support the feasibility of detecting selective activation of the rolandic cortex, even in the clinical setting, leading the authors to suggest the usefulness of this widely available technique in surgical planning.

Adult↗
PubMed2004

Multimodal functional mapping of sensorimotor cortex prior to resection of an epileptogenic perirolandic lesion.

The effects of chronic epileptogenic lesions on functional anatomy are under debate. Our recent experience during mapping and resection of a lesion in sensorimotor cortex supports the idea that epileptogenic lesions may prompt development of alternate cortical motor representations. Multimodal mapping may uncover alternate areas of functionality that make surgery feasible even when conventional neuroanatomy suggests otherwise. Newer methods such as electrocorticographic spectral analysis may complement traditional electrical cortical stimulation mapping.

Adolescent↗
PubMed2004

The effect of sensorimotor activation on functional connectivity mapping with MRI.

The correlations in the fluctuations in the blood oxygenation level-dependent (BOLD) MRI signal between anatomically distinct regions of the cortex that are known components of functional systems have been previously studied as possible indicators of functional connectivity. The objective of this study was to examine the effect of sensorimotor brain activity, as assessed by task-based functional magnetic resonance imaging (fMRI), on functional connectivity indices in the same region. Regions of activation for sequential finger motion were determined using a task-based, block-design fMRI study. Functional connectivity measurements based on interregional correlations were acquired at rest and during continuous, sequential finger motion. Connectivity indices were determined using normalized mean correlations within and between three regions of interest activated for the finger motion task. Connectivity indices were also determined for a control region that was not activated for the task. Continuous motor tasks performed during BOLD measurements did not significantly affect the functional connectivity as compared to the connectivity at rest within or between regions known to be activated by the task. However, there appeared to be a trend suggesting a slight reduction in connectivity indices during the motor task. The connectivity within and between those areas not activated for the task remained unchanged between conditions. These results suggest that in the motor system investigated, the recruitment of neurons to perform a specific task may moderately reduce the degree of hemodynamic coupling within and between regions.

Adult↗
PubMed2005

Assessment of infant oral sensorimotor and swallowing function.

The development of feeding and swallowing is the result of a complex interface between the developing nervous system, various physiological systems, and the environment. The purpose of this article is to review the neurobiology, development, and assessment of feeding and swallowing during early infancy. In recent years, there have been exciting advances in our understanding of the physiology and neurological control of feeding and swallowing. These advances may prove useful in furthering our understanding of the pathophysiology of dysphagia in infancy. Progress in developing standardized, reliable, and valid measures of oral sensorimotor and swallowing function in infancy has been slow. However, there have been significant advances in the instrumental analysis of feeding and swallowing disorders in infancy, including manometric analyses of sucking and swallowing, measures of respiration during feeding, videofluoroscopic swallow evaluations, ultrasonography, and flexible endoscopic examination of swallowing. Further efforts are needed to develop clinical evaluative measures of dysphagia in infancy.

Deglutition↗
PubMedDate not supplied

The Innsbruck Sensorimotor Activator and Regulator (ISMAR): construction of an intraoral appliance to facilitate ingestive functions.

Oral sensorimotor therapy is practiced widely with children who have neuromotor impairments, such as cerebral palsy and eating problems. Although improvement in ingestive skills can be achieved in the short term (5 months), long-term effects (over 12 months) remain to be examined. Interventions with intraoral appliances are used in children with moderate impairments of the oral-motor system and offer an opportunity for long-term treatment. Instead of the daily oral sensorimotor exercises, which must be provided by a qualified therapist, the intraoral appliance is worn during the night, so that the "therapy" is initiated and controlled by the child. The purpose of this paper is to describe the appliance: its prescription, fabrication and therapeutic use. A case study illustrates that improvement in ingestive skills, efficiency of eating, and marked weight gain can be achieved.

Cerebral Palsy↗
PubMed2006

Decreased desychronisation during self-paced movements in frequency bands involving sensorimotor integration and motor functioning in Parkinson's disease.

This study examined sensorimotor integration and motor functioning in seven patients with Parkinson's disease (PD) who had mild symptoms, and seven age-matched controls. Neuro-oscillations were recorded by high-density 128-channel electroencephalography (EEG). Participants were required to perform two tasks: simple tapping of the index finger and thumb and a complex Luria finger apposition task. Both tasks were performed unimanually and bimanually. There were no significant group differences in the task-related power (TRPow) within alpha 1 (mu1) or in beta 1 frequencies (beta1). In contrast, there were significant group differences in the alpha 2 (mu2) and beta 2 frequencies (beta2). Patients had less desychronisation than controls at the electrodes covering the central regions of the scalp. Alpha 2 and beta 2 frequencies have been associated with task-specific sensorimotor integration and motor function, respectively. This activity difference in patients with Parkinson's disease may be due to deficits in sensorimotor integration.

Aged↗
PubMed1996

Functional localization of sensorimotor cortex by somatosensory evoked potentials produced by femoral nerve stimulation.

Cortical somatosensory evoked potentials (SSEPs) can be used to localize the central sulcus during a craniotomy. In particular, contralateral median nerve stimulation producing SSEPs can disclose the location of the central sulcus around the sensorimotor hand representation area. However, the median nerve cannot be stimulated in patients who undergo craniotomy at locations other than the hand representation area. The present study attempts to localize the central sulcus in the lateral surface of the brain near the interhemispheric fissure by stimulating the contralateral femoral nerve to produce SSEPs. Somatosensory evoked potentials were recorded between the superior lip of the interhemispheric fissure and 1.5 to 2 cm laterally in the cortex. Only seven of the 12 patients studied showed a phase reversal of the initial component across the central sulcus. The polarity was negative in the postcentral gyrus and positive in the precentral gyrus. The other five patients did not show a phase reversal of the initial component across the central sulcus. The amplitude was highest in the postcentral gyrus and the polarity was positive. Based on these results, the authors hypothesize that stimulating the contralateral femoral nerve to produce SSEPs and then analyzing the distribution of the SSEPs may provide a method for functional localization of the sensorimotor cortex around the interhemispheric fissure during craniotomy.

Journal Article↗
PubMed2000

Long-term changes of GABAergic function in the sensorimotor cortex of amputees. A combined magnetic stimulation and 11C-flumazenil PET study.

Primary sensory and motor areas of the cerebral cortex contain organised maps of the body. These maps appear to reorganise after damage to the peripheral parts of the sensory or motor systems, so that the cortical representation of undamaged structures expands at the expense of the damaged parts. Several studies in animals have suggested that decreased activity of the inhibitory GABAergic neurones is responsible for driving these changes. However, whether similar mechanisms sustain the effects in the longer term in humans is unknown. The present study addressed this question by examining reorganisation of sensorimotor areas of cortex in six unilateral upper limb amputees several years after the initial injury. We measured two independent indices of GABAergic function. Volumes of distribution of GABA(A) receptors were determined from 11C-flumazenil binding measured with positron emission tomography (PET). The strength of inhibition in the motor cortex was measured with paired-pulse transcranial magnetic stimulation. In the six amputees taken as a whole and compared with 24 normal subjects, there was a highly significant increase in 11C-flumazenil binding in the upper limb region of primary sensorimotor cortex bilaterally and in medial frontal cortex of the hemisphere contralateral to the amputation. Surprisingly, however, there was no change in the time course or strength of intra-cortical inhibition in the motor cortex of the amputees compared with matched control subjects. The increased 11C-flumazenil binding may reflect up-regulation of GABA(A) receptors to compensate for a decrease in the GABA content or activity of inhibitory neurones. Up-regulation of GABA(A) receptors may also indicate that long-term changes require stabilisation of cortical organisation.

Adult↗
PubMed2005

Functional somatotopy in sensorimotor cortex.

In an effort to understand the highly distributed somatotopy of primary motor cortex, this review draws on principles derived from studies of auditory, visual and somatosensory cortical areas. In each case, a behaviorally important feature or function is overlaid in multiple locations on an underlying topographic map of the peripheral sensory surface. Recent studies of hand muscle synergies suggest the types of two-dimensional functional axes that might reasonably be mapped to the two-dimensional surface of the primary motor cortex. However, other research emphasizes that even a functional somatotopy must be extremely flexible.

Animals↗
PubMed2001

Functional neuroanatomical correlates of hysterical sensorimotor loss.

Hysterical conversion disorders refer to functional neurological deficits such as paralysis, anaesthesia or blindness not caused by organic damage but associated with emotional "psychogenic" disturbances. Symptoms are not intentionally feigned by the patients whose handicap often outweighs possible short-term gains. Neural concomitants of their altered experience of sensation and volition are still not known. We assessed brain functional activation in seven patients with unilateral hysterical sensorimotor loss during passive vibratory stimulation of both hands, when their deficit was present and 2-4 months later when they had recovered. Single photon emission computerized tomography using (99m)Tc-ECD revealed a consistent decrease of regional cerebral blood flow in the thalamus and basal ganglia contralateral to the deficit. Independent parametric mapping and principal component statistical analyses converged to show that such subcortical asymmetries were present in each subject. Importantly, contralateral basal ganglia and thalamic hypoactivation resolved after recovery. Furthermore, lower activation in contralateral caudate during hysterical conversion symptoms predicted poor recovery at follow-up. These results suggest that hysterical conversion deficits may entail a functional disorder in striatothalamocortical circuits controlling sensorimotor function and voluntary motor behaviour. Basal ganglia, especially the caudate nucleus, might be particularly well situated to modulate motor processes based on emotional and situational cues from the limbic system. Remarkably, the same subcortical premotor circuits are also involved in unilateral motor neglect after organic neurological damage, where voluntary limb use may fail despite a lack of true paralysis and intact primary sensorimotor pathways. These findings provide novel constraints for a modern psychobiological theory of hysteria.

Adolescent↗
PubMed1996

Monitoring of task performance during functional magnetic resonance imaging of sensorimotor cortex at 1.5 T.

Functional magnetic resonance imaging (fMRI) has found widespread clinical interest. Difficulties in clinical use of the fMRI technique arise, considering the lack of knowledge about activation task performance. This accounts especially for sensorimotor activation studies, in which performance of the sensorimotor activation task is-if at all-usually rated visually by subjective or semiquantitative methods (i.e., defining categories of performance such as neurological soft signs scales). Recently, instrumental methods for the measurement and analysis of motor performance have been developed. Pronation/supination (hand rotation) movement was shown to be an easily measurable and promising motor task. We have adapted a mechanic device (pronation/supination device, PSD) to monitor motor performance during the fMRI experiment. In a feasibility study, an investigation of fMRI activation strength dependence of sensorimotor cortices and supplementary motor area upon task frequency (25, 50, and 75 cycles/min) was carried out on 10 right-handed healthy volunteers. Furthermore, the authors report the observation of stimulus-induced activation changes in the cerebellum during pronation/supination movement.

Hand↗
PubMedDate not supplied

Interneuronal functional associations in the sensorimotor cortex of dogs.

The interneuronal functional associations were studied in two dogs with Nichrome semi-microelectrodes implanted into the deep layers of the motor and somatosensory regions of the cerebral cortex using the method of cross-correlation analysis. For this purpose the impulse activity of individual neurons was distinguished by form from the background multineuronal activity using the spike recognition technique. Values of a 0.5 and 1 msec-wide bin, and thereafter with a 1 msec step up to 40 msec, were used to plot the cross-interval histograms. The maximal analysis epoch was 2000 msec. The cross-interval associations were monotypal in character; they all presented fairly narrow extrema which were clearly distributed across three time ranges: short-latency associations up to 10 msec; associations with a medium latency up to 80 msec; and associations with late delays, greater than 80 msec. The fairly narrow peak of the association, especially in the case of associations with late delays, was a very difficult phenomenon to explain from the point of view of traditional theoretical perspectives. It is hypothesized that a mechanism exists in the cortex which is responsible for strictly synchronized and highly efficient synaptic transmission.

Animals↗
PubMed2005

Neurexophilin 3 is highly localized in cortical and cerebellar regions and is functionally important for sensorimotor gating and motor coordination.

Neurexophilin 3 (Nxph3) is a specific ligand of synaptic alpha-neurexins that are essential for efficient neurotransmitter release. Previous biochemical work demonstrated that Nxph3 interacts with an extracellular domain of alpha-neurexins in a tight complex; however, no information is available on the localization or functional role of Nxph3 in the brain. Here, we generated lacZ reporter gene knock-in mice to investigate the distribution of Nxph3 at the single-cell level and Nxph3 knockout mice to examine its functional importance. Nxph3 expression was restricted mostly to subplate-derived neurons in cortical layer 6b, granule cells in the vestibulocerebellum, and Cajal-Retzius cells during development. Colabeling experiments demonstrated that neurons expressing Nxph3 do not belong to a uniform cell type. Morphological analyses and systematic behavioral testing of knockout mice revealed no anatomical defects but uncovered remarkable functional abnormalities in sensory information processing and motor coordination, evident by increased startle response, reduced prepulse inhibition, and poor rotarod performance. Since Nxph3-deficient mice behaved normally while performing a number of other tasks, our data suggest an important role for Nxph3 as a locally and temporally regulated neuropeptide-like molecule, presumably acting in a complex with alpha-neurexins in select neuronal circuits.

Alleles↗
PubMed1999

Assessment of functional MR imaging in neurosurgical planning.

BACKGROUND AND PURPOSE: Presurgical sensorimotor mapping with functional MR imaging is gaining acceptance in clinical practice; however, to our knowledge, its therapeutic efficacy has not been assessed in a sizable group of patients. Our goal was to identify how preoperative sensorimotor functional studies were used to guide the treatment of neuro-oncologic and epilepsy surgery patients. METHODS: We retrospectively reviewed the medical records of 46 patients who had undergone preoperative sensorimotor functional MR imaging to document how often and in what ways the imaging studies had influenced their management. Clinical management decisions were grouped into three categories: for assessing the feasibility of surgical resection, for surgical planning, and for selecting patients for invasive functional mapping procedures. RESULTS: Functional MR imaging studies successfully identified the functional central sulcus ipsilateral to the abnormality in 32 of the 46 patients, and these 32 patients are the focus of this report. In epilepsy surgery candidates, the functional MR imaging results were used to determine in part the feasibility of a proposed surgical resection in 70% of patients, to aid in surgical planning in 43%, and to select patients for invasive surgical functional mapping in 52%. In tumor patients, the functional MR imaging results were used to determine in part the feasibility of surgical resection in 55%, to aid in surgical planning in 22%, and to select patients for invasive surgical functional mapping in 78%. Overall, functional MR imaging studies were used in one or more of the three clinical decision-making categories in 89% of tumor patients and 91% of epilepsy surgery patients. CONCLUSION: Preoperative functional MR imaging is useful to clinicians at three key stages in the preoperative clinical management paradigm of a substantial percentage of patients who are being considered for resective tumor or epilepsy surgery.

Adolescent↗