SEARCH · PubMed Health

Results for “sensorimotor function”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,153 records · Page 64Linked to original sources

PubMed1977

[Mechanisms of participation of the sensomotor cortex in controlling movements].

Neuromorphological, neurophysiological and biomechanical studies in cats revealed cortical structural neuronal modules and functional units of different grades of complexity. Single systemic principle was determined for the sensorimotor cortex activity: structurally organized neuronal modules, having distributed outputs, can be involved in different functional units for purposeful movements. Specific lemniscal signals concerning the movements are the factor which filters inflow of teleceptive information to the neuronal modules and determines exact torographical relations of cortical motor outputs.

Animals↗

PubMed2003

The elusive concept of brain connectivity.

Neurons and neural populations do not function as islands onto themselves. Rather, they interact with other such elements through their afferent and efferent connections in an orchestrated manner so as to enable different sensorimotor and cognitive tasks to be performed. The concept of functional connectivity and the allied notion of effective connectivity were introduced to designate the functional strengths of such interactions. Functional neuroimaging methods, especially PET and fMRI, have been used extensively to evaluate the functional connectivity between different brain regions. After providing a brief historical review of these notions of brain connectivity, I argue that the conceptual formulations of functional and effective connectivity are far from clear. Specifically, the terms functional and effective connectivity are applied to quantities computed on types of functional imaging data (e.g., PET, fMRI, EEG) that vary in spatial, temporal, and other features, using different definitions (even for data of the same modality) and employing different computational algorithms. Until it is understood what each definition means in terms of an underlying neural substrate, comparisons of functional and/or effective connectivity across studies may appear inconsistent and should be performed with great caution.

Brain↗

PubMed2003

Does an imbalance between the dorsal and ventral striatopallidal systems play a role in Tourette's syndrome? A neuronal circuit approach.

Tourette's syndrome is characterized by simple, involuntary muscle contractions and/or more complex movements or stereotyped behaviors, including vocalizations. There are strong indications that the basal ganglia play an important role in the pathophysiology of Tourette's syndrome. The present account reviews the functional anatomy of the basal ganglia, with an emphasis on the prefrontal cortex-ventral striatopallidal system. Different parts of the basal ganglia and thalamocortical system, with a focus on the premotor and prefrontal cortices, are connected with each other via parallel, functionally segregated basal ganglia-thalamocortical systems. These parallel circuits, representing sensorimotor, cognitive and emotional-motivational behavioral processes, are connected with each other through specific pathways that serve to integrate these various functions. In the context of the discussion on the pathophysiological mechanisms that lead to the expression of tics, emphasis is placed on the pathways that lead from the ventral striatum via the dopaminergic substantia nigra to the dorsal striatum. The dorsal striatum is crucial for habit formation. A conclusion of this overview of the anatomical organization of the basal ganglia is that via dopaminergic pathways limbic-relation information can influence the expression of (fragments of) motor and behavioral repertoires. Whether such mechanisms indeed play a role in the expression of tics in Tourette's syndrome remains to be established.

Animals↗

PubMed2005

Surgical resection of an epileptogenic cortical dysplasia in the deep foot sensorimotor area.

Epileptogenic foci in the foot/leg motor area of cortex are rarely resected, due to the risks of the surgical procedures. A 31-year-old right-handed man with cortical dysplasia deep in the central sulcus suffered from disturbances in walking due to frequent daily seizures. Following subdural electrode implantation to define the epileptogenic area and assess cortical function, limited regions of cortex were removed from the foot/leg primary motor and sensory areas under local anesthesia until the epileptiform discharges disappeared. Postoperative motor weakness and sensory disturbances completely resolved within 2 weeks and 2 months, respectively; the patient has been free from seizures for more than a year and a half postsurgery. Intraoperative examination demonstrated that small and moderate cortical dysplasia in the depths of the central sulcus exhibits both intrinsic epileptogenicity and function. Focused resection of the lower extremity of the sensorimotor area may be a surgical strategy for intractable epilepsy if resolution of clinical symptoms with minimal dysfunction due to the limited size of the resection is expected to follow surgery.

Adult↗

PubMed2004

A detrimental role for nitric oxide synthase-2 in the pathology resulting from acute cerebral injury.

Nitric oxide (NO) synthesized from the inducible isoform of nitric oxide synthase (NOS-2) has been suggested to play both beneficial and deleterious roles in various neuropathologies. To define the role of nitric oxide in traumatic brain injury, we subjected male mice lacking a functional NOS-2 gene (NOS-2-/-) and their wild-type littermates (NOS-2+/+) to mild or severe aseptic cryogenic cerebral injury. Expression of NOS-2 mRNA and protein was observed in NOS-2+/+ animals following injury. Lesion volume (as measured by histology and brain imaging) and neurological outcome (using motor and cognitive behavioral paradigms) were assessed at various times after injury. While magnetic resonance imaging revealed the extent of edema of the 2 genotypes to be similar, histology showed a reduced (32%) lesion volume in severely injured NOS-2-/- compared with NOS-2+/+ mice. In addition, NOS-2-/- mice showed significant improvements in both contralateral sensorimotor deficits (grid test: p = 0.011) and cognitive function (Morris water maze: p = 0.009) after severe injury compared to their wild-type littermates. This indicates that lesion volume is reduced and neurological recovery is improved after acute traumatic injury in mice lacking a functional NOS-2 gene, and strongly suggests that the post-trauma production of NO from this source contributes to neuropathology.

Acute Disease↗

PubMed2005

Experimental diabetes attenuates cerebral cortical-evoked forelimb motor responses.

Poorly controlled diabetes leads to debilitating peripheral complications, including retinopathy, nephropathy, and neuropathy. Chronic diabetes also impairs the central nervous system (CNS), leading to measurable deficits in cognition, somatosensory, and motor function. The cause of diabetes-associated CNS impairment is unknown. In this study, sustained hyperglycemia resulting from insulin deficiency was shown to contribute to CNS motor dysfunction. Experimental diabetes was induced in rats by streptozotocin (STZ) injection. CNS motor function was assessed by intracortical microstimulation of the sensorimotor cortex. Experimental diabetes significantly (P < 0.01; n = 14) attenuated the number of motor cortical sites eliciting forelimb movements. The net area of the motor cortex representing the forelimb in diabetic rats was significantly reduced (4.0 +/- 0.5 [control] vs. 2.4 +/- 0.4 [STZ] mm(2); P < 0.05). Experimental diabetes attenuated the activation of some, but not all, forelimb motor cortical neurons. Insulin treatment of diabetic rats prevented the attenuation of cortical-evoked forelimb responses. Peripheral nerve-evoked responses were unaffected by this short period of diabetes, suggesting the absence of peripheral nerve dysfunction. This study showed that metabolic imbalance resulting from insulin deficiency elicits a marked attenuation of cortical-evoked motor function. Uncontrolled hyperglycemia, deficiencies of central insulin, or both may contribute to corticospinal motor dysfunction.

Animals↗

PubMed1998

Cognitive and motor slowing in Alzheimer's disease and geriatric depression.

While response slowing on psychological tasks is a symptom of both depression and Alzheimer's disease (AD), the underlying mechanisms may be quite different: a slowing of cognitive processing in AD and a motor retardation in depression. This hypothesis was tested by examining the rate at which participants performed a simple cognitive operation: subvocal pronunciation. Participants were shown words of between one and three syllables and were asked to decide whether each word ended in a particular sound. This task required participants to transform the written word into its phonological representation, an operation thought to involve subvocal pronunciation. Decision time rose linearly with the number of syllables in all three subject groups. The linear function of the AD patients had a significantly greater slope, indicating a slower rate of subvocal pronunciation, whereas the slope was the same for the normal old and depressed. Both the depressed and AD patients had a higher intercept than the normal old, suggesting a sensorimotor slowing. After treatment, the intercept of the linear function for depressed patients fell, but there was no change in the slope. Thus, this study suggests that AD produces a slowing in both cognitive and motor processes, whereas depression results solely in a motor retardation.

Aged↗

PubMed2000

Computational approaches to sensorimotor transformations.

Behaviors such as sensing an object and then moving your eyes or your hand toward it require that sensory information be used to help generate a motor command, a process known as a sensorimotor transformation. Here we review models of sensorimotor transformations that use a flexible intermediate representation that relies on basis functions. The use of basis functions as an intermediate is borrowed from the theory of nonlinear function approximation. We show that this approach provides a unifying insight into the neural basis of three crucial aspects of sensorimotor transformations, namely, computation, learning and short-term memory. This mathematical formalism is consistent with the responses of cortical neurons and provides a fresh perspective on the issue of frames of reference in spatial representations.

Animals↗

PubMed2005

Gait disorders: search for multiple causes.

Gait disorders predict functional decline in older adults. They are often the result of multiple causes, so a full assessment should consider different sensorimotor levels and should include a focused physical examination and evaluation of functional performance. Exercise and medical and surgical interventions are effective and can reduce the degree of gait disorder, but usually not without some residual impairment. Orthoses and mobility aids are also important interventions to consider.

Age Factors↗

PubMed1999

Oxytocin modulates psychotomimetic-induced deficits in sensorimotor gating.

Oxytocin plays an important role in the regulation of normal cognitive functions and behaviors, which are disturbed in schizophrenia. Several studies suggest that oxytocinergic function is abnormal in schizophrenia patients. Thus, oxytocin may be involved in the pathophysiology associated with this disorder. This study investigated the regulatory effects of oxytocin on deficits in prepulse inhibition (PPI) associated with schizophrenia. Prepulse inhibition (PPI) is an operational measure of sensorimotor gating which can be measured across many species. PPI is the normal suppression of the startle reflex when the intense startling stimulus ("pulse") is immediately preceded by a weaker stimulus ("prepulse"). Subcutaneously administered oxytocin (0.04-1.0 mg/kg) dose-dependently restored PPI that had been reduced in rats by dizocilpine, a non-competitive NMDA antagonist, and by amphetamine, an indirect dopamine agonist. Oxytocin did not produce a significant effect on baseline PPI or PPI decreased by the direct dopamine agonist, apomorphine. The underlying startle response amplitude was also not significantly altered by oxytocin. These results suggest that oxytocin may play an important role in the modulation of dopaminergic and glutamatergic regulation of PPI, and that it may act as a novel endogenous antipsychotic.

Amphetamine↗

PubMed1992

A cross-cultural test of the validity of occupational therapy assessments with patients with schizophrenia.

The validity and use of psychosocial assessments in occupational therapy are ongoing concerns (Moyer, 1984) and were the focus of this study. Fifty African patients with schizophrenia and 10 nondysfunctional African volunteers took an an assessment battery that included the Schroeder, Block, Campbell Adult Psychiatric Sensory Integration Evaluation (SBC) (Schroeder, Block, Trottier, & Stowell, 1978), a daily activity, work, and leisure activity interview based on the Model of Human Occupation (Kielhofner, 1985), and a culture-specific test of functional performance. Data on subjects' psychiatric histories and demographics were collected. Rationale for the assessments used, methods for devising the functional assessment, methods and procedures for data collection, and analysis are presented. A stronger relationship was found to exist between subjects' performances on the SBC and the functional activity test than between interviews based on the Model of Human Occupation and the functional activity test, both for patients and for the whole sample. All assessments were found to differentiate between patients and nonpatients, although the SBC was the best discriminator. Among psychiatric history variables, the strongest relationships were between measures of seriousness of illness and both the SBC and functional activity assessment. The most effective way to measure performance dysfunction and seriousness of illness in persons with schizophrenia was to measure the underlying sensorimotor impairment or to use a culture-specific test of functional performance.

Adult↗

PubMed1986

How does the limbic system assist motor learning? A limbic comparator hypothesis.

This paper offers a new hypothesis about how the limbic system might assist motor learning. It is proposed that interactions of limbic and sensorimotor-related systems are essential for learning what to do in a motor task (appropriate, relevant behavior) and how to do it best (motor skill). Limbic modulations of sensorimotor-related neural centers are envisaged to result from comparisons in various neural centers of converging inputs from the relevance-sensitive amygdala and from corollary, cortically-modulated recipients of amygdaloid information. Such comparisons of relatively 'raw' limbic inputs and their 'processed', corollary forms could be achieved in a side-loop manner resembling that in the cerebellum. This 'limbic comparator' hypothesis was prompted by studies of motor learning that show how monkeys develop skill only after gaining insight into appropriate, task-related behavior, and that inappropriate behavior during transition into the insightful state produces 'error' signals from the anterior cingulate cortex. Known sites of limbic projections that could serve corollary comparisons are examined with regard to their possible influence on motivation, appropriate, task-related behavior and motor skill. Anatomical and functional tests of convergence and comparison in sensorimotor-related neural centers are suggested in order to stimulate investigations of the limbic comparator hypothesis.

Animals↗

PubMed1999

Clinical Applications of [(15)O] H(2)O PET Activation Studies.

Localization of eloquent cortical regions is an important aspect of neurosurgical practice. When lesions lie close to or within areas such as somatosensory, motor or language cortex, the goal of surgical treatment is maximal resection without causing neurological deficit. Hence precise functional mapping combined with accurate delineation of the extent of pathology is important for deciding whether surgery is feasible at all and defining the safe limit of resection and the optimal operative approach. In addition, when the electroclinical pattern of intractable seizures suggests a specific localization in sensorimotor cortex (e.g., seizures originating in the face area), functional mapping may be of use in directing the surgical treatment at the seizure focus. Activation studies using positron emission tomography (PET) and the tracer [(15)O] labeled water ([(15)O]H(2)O) can be used in presurgical planning and in intraoperative surgical guidance in individual patients. The use of PET technology for these purposes is critically dependent on advances in registration or alignment of images acquired using different modalities; the development of neurosurgical guidance devices; and the development of methods of statistical analysis suitable for use in single subjects.

Journal Article↗

PubMed2003

Task-dependent modulations of cortical oscillatory activity in human subjects during a bimanual precision grip task.

Oscillations are a widespread feature of normal brain activity and have been reported at a variety of different frequencies in different neuronal systems. The demonstration that oscillatory activity is present in motor command signals has prompted renewed interest in the possible functions of synchronous oscillatory activity within the primate sensorimotor system. In the current study, we investigated task-dependent modulations in coupling between sensorimotor cortical oscillators during a bimanual precision grip task. The task required a hold-ramp-hold pattern of grip force to be exerted on a compliant object with the dominant right hand, while maintaining a steady grip with the nondominant hand. We found significant task-related modulation of 15- to 30-Hz coherence between magnetoencephalographic (MEG) activity recorded from the left sensorimotor cortex and electromyographic (EMG) activity in hand muscles on the right side. This coherence was maximal during steady hold, but disappeared during the ramp movements. Interestingly coherence between the right sensorimotor MEG and left-hand EMG showed a similar, although less deeply modulated, task-related pattern, even though this hand was maintaining a simple steady grip. No significant ipsilateral MEG-EMG coherence was observed in the 15- to 30-Hz passband for either hand. These results suggest that the cortical oscillators in the two sensorimotor cortices are independent to some degree but that they may share a common mechanism that attenuates the cortical power in both hemispheres in the 15- to 30-Hz range during movements of one hand. The results are consistent with the hypothesis that oscillatory activity in the motor system is important in resetting the descending motor commands needed for changes in motor state, such as those that occur in the transition from movement to steady grip.

Adult↗

PubMed2000

Synaptic organisation of the basal ganglia.

The basal ganglia are a group of subcortical nuclei involved in a variety of processes including motor, cognitive and mnemonic functions. One of their major roles is to integrate sensorimotor, associative and limbic information in the production of context-dependent behaviours. These roles are exemplified by the clinical manifestations of neurological disorders of the basal ganglia. Recent advances in many fields, including pharmacology, anatomy, physiology and pathophysiology have provided converging data that have led to unifying hypotheses concerning the functional organisation of the basal ganglia in health and disease. The major input to the basal ganglia is derived from the cerebral cortex. Virtually the whole of the cortical mantle projects in a topographic manner onto the striatum, this cortical information is 'processed' within the striatum and passed via the so-called direct and indirect pathways to the output nuclei of the basal ganglia, the internal segment of the globus pallidus and the substantia nigra pars reticulata. The basal ganglia influence behaviour by the projections of these output nuclei to the thalamus and thence back to the cortex, or to subcortical 'premotor' regions. Recent studies have demonstrated that the organisation of these pathways is more complex than previously suggested. Thus the cortical input to the basal ganglia, in addition to innervating the spiny projection neurons, also innervates GABA interneurons, which in turn provide a feed-forward inhibition of the spiny output neurons. Individual neurons of the globus pallidus innervate basal ganglia output nuclei as well as the subthalamic nucleus and substantia nigra pars compacta. About one quarter of them also innervate the striatum and are in a position to control the output of the striatum powerfully as they preferentially contact GABA interneurons. Neurons of the pallidal complex also provide an anatomical substrate, within the basal ganglia, for the synaptic integration of functionally diverse information derived from the cortex. It is concluded that the essential concept of the direct and indirect pathways of information flow through the basal ganglia remains intact but that the role of the indirect pathway is more complex than previously suggested and that neurons of the globus pallidus are in a position to control the activity of virtually the whole of the basal ganglia.

Animals↗

PubMed2000

Evidence for adaptive functional changes in the cerebral cortex with axonal injury from multiple sclerosis.

Axonal injury occurs even in the earliest stages of multiple sclerosis. Magnetic resonance spectroscopic imaging (MRSI) measurements of brain N:-acetylaspartate (NAA), a marker of axonal integrity, show that this axonal injury can occur even in the absence of clinically evident functional impairments. To test whether cortical adaptive responses contribute to the maintenance of normal motor function in patients with multiple sclerosis, we performed MRSI and functional MRI (fMRI) examinations of nine multiple sclerosis patients who had unimpaired hand function. We found that activation of the ipsilateral sensorimotor cortex with simple hand movements was increased by a mean of fivefold relative to normal controls (n = 8) and that the extent of this increase was strongly correlated (sigma = -0.93, P = 0.001) with decreases in brain NAA. These results suggest that compensatory cortical adaptive responses may help to account for the limited relationship between conventional MRI measures of lesion burden and clinical measures of disability, and that therapies directed towards promoting cortical reorganization in response to brain injury could enhance recovery from relapses of multiple sclerosis.

Aspartic Acid↗

PubMed1996

The effects of amphetamine on recovery of function after cortical damage in the rat depend on the behavioral requirements of the task.

The effects of amphetamine on the recovery of function following unilateral lesions of the rat somatic sensorimotor cortex (SMC) were examined. Rats with large SMC were tested on two measures of locomotor placing: the beam-walking test and the foot-fault test. Amphetamine produced an immediate and enduring facilitation of recovery on the beam-walking test. In contrast, the drug had no effect on the rats' ability to accurately place the forelimbs on the rungs of the elevated grid during locomotion on the foot-fault test. These data suggest that amphetamine may facilitate recovery when the requirements of the task produce a deficit in the initiation of locomotion but not when the animal is required to use somatosensory and proprioceptive cues to guide performance on the task. A second group of rats with smaller SMC lesions was evaluated with tactile-placing tests and the bilateral-tactile stimulation task. The forelimb placing reaction is elicited by unilateral tactile stimulation of the vibrissae or forelimb, whereas the ipsilateral asymmetry observed on the bilateral-tactile stimulation test has been interpreted as an impairment in processing stimuli presented on both sides of the body. On two measures of forelimb placing amphetamine produced a facilitation of recovery, but restoration of function was not observed during the period of drug intoxication. In contrast, amphetamine had no effect on recovery of function on the bilateral-tactile stimulation test. Taken together, these data suggest that the behavioral requirements of the task are an important factor in determining the facilitatory effects of amphetamine on recovery of function.

Animals↗

PubMed2001

Sensorimotor mapping of the human cerebellum: fMRI evidence of somatotopic organization.

Functional magnetic resonance imaging (fMRI) was employed to determine areas of activation in the cerebellar cortex in 46 human subjects during a series of motor tasks. To reduce the variance due to differences in individual anatomy, a specific transformational procedure for the cerebellum was introduced. The activation areas for movements of lips, tongue, hands, and feet were determined and found to be sharply confined to lobules and sublobules and their sagittal zones in the rostral and caudal spino-cerebellar cortex. There was a clear symmetry mirroring at the midline. The activation mapped as two distinct homunculoid representations. One, a more extended representation, was located upside down in the superior cerebellum, and a second one, doubled and smaller, in the inferior cerebellum. The two representations were remarkably similar to those proposed by Snider and Eldred [1951] five decades ago. In the upper representation, an intralimb somatotopy for the right elbow, wrist, and fingers was revealed. The maps seem to confirm earlier electrophysiological findings of sagittal zones in animals. They differ, however, from micromapping reports on fractured somatotopic maps in the cerebellar cortex of mammals. We assume that the representations that we observed are not solely the result of spatial integration of hemodynamic events underlying the fMRI method and may reflect integration of afferent peripheral and central information in the cerebellar cortex.

Adolescent↗