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PubMed1981

Lateral hypothalamic regulation of electrocortical activity.

The EEG power spectrum of normal and split-brain cats was analysed before and after unilateral hypothalamic lesion at sites which prior to lesion had ICSS or aversive properties on stimulation, and which gave rise to sensorimotor neglect after lesion. A filter-gain function was calculated to describe the lesions' effect upon the ipsilateral EEG spectrum in stable conditions, and was found to be approximated by a specific gamma function. This partially defines the action that the lateral hypothalamus may exert on electrocortical activity.

Animals↗
PubMed1985

Hippocampal theta rhythm during paradoxical sleep. Effects of afferent stimuli and phase relationships with phasic events.

Hippocampal theta rhythm and phasic events (i.e., vibrissa, body and ocular movements and ponto-geniculo-occipital (PGO) spikes) were recorded in rats and cats during paradoxical sleep (PS). Single pulse stimulation of some afferent structures (i.e., medial septum, mesencephalic reticular formation and entorhinal cortex) were performed during PS. Hippocampal afferent stimulation determined the phase resetting of hippocampal theta waves during PS in a similar form to that during wakefulness. All studied phasic events tend to occur at a preferred phase of the theta cycle. Theta waves begin to synchronize some time before movements. These results suggest that PS is an active state during which hippocampal theta rhythm may have functions similar to those occurring during wakefulness, e.g. sensorimotor integration.

Afferent Pathways↗
PubMed1995

Influence of place learning on somatostatin levels in the rat brain following environmental deprivation.

We have previously reported increased somatostatin levels in the cerebral cortex of rats housed in impoverished environment and subsequently subjected to a behavioural testing procedure, consisting of open-field exposure and spatial learning. The aim of the present study was to evaluate the degree of neurochemical specificity of the activation of somatostatin neurotransmission and to examine whether the altered levels were due to learning stimulation. Adult rats, previously housed individually for 30 days, were exposed to repeated sessions of a spatial learning task (2 days or 14 days) or repeated sessions of free swimming (14 days). The training sessions of the 14 day group consisted in recurrently changed position of the platform in a learning-set paradigm. Our data showed increased somatostatin immunoreactivity, and unchanged substance P immunoreactivity in the posterior part of the cerebral cortex. However, somatostatin levels increased to a similar extent following 14 days of repeated spatial learning sessions as free swimming sessions. We conclude that the activity of the cortical somatostatin system appears to be sensitive to environmentally induced sensorimotor stimulation in general, rather than learning per se. Thus, external stimulation of early clinical dementia patients with preserved sensorimotor receptivity, in an attempt to restore cognitive function, might be associated with altered somatostatin levels.

Analysis of Variance↗
PubMed2005

Processing of spatial visual information along the pathway between the suprageniculate nucleus and the anterior ectosylvian cortex.

This study describes the visual information coding ability of single neurons in the suprageniculate nucleus (Sg), and provides new data concerning the visual information flow in the suprageniculate/anterior ectosylvian pathways of the feline brain. The visual receptive fields of the Sg neurons have an internal structure rather similar to that described earlier in the anterior ectosylvian visual area (AEV). The majority of the Sg units can provide information via their discharge rate at the site of the visual stimulus within their large receptive fields. This suggests that they may serve as panoramic localizers. The sites of maximum responsivity of the Sg neurons are distributed over the whole investigated part of the visual field. There is no significant difference between the distributions of spatial location of maximum sensitivity of the AEV and the Sg neurons. The mean visual response latency of the Sg units was found to be significantly shorter than the mean latency of the AEV neurons, but there was no difference between the shortest latency values of the thalamic and the cortical single-units. This suggests that the visual information flows predominantly from the Sg to the AEV, though the cortico-thalamic route is also active. The Sg seems to represent a thalamic nucleus rather similar in function to both the first-order relays and the higher-order thalamic nuclei. These results, together with the fact that the superior colliculus provides the common ascending source of information to the suprageniculate/anterior ectosylvian pathway, suggest a unique function of the AEV and the Sg in sensorimotor integration.

Action Potentials↗
PubMed2000

Functional assessments in mice and rats after focal stroke.

This paper presents a comprehensive assessment of sensorimotor deficits in the mouse after focal ischaemia induced by occlusion of the middle cerebral artery. Twenty four hours after induction of middle cerebral artery occlusion, mice showed deficits in a range of sensory and motor tasks as assessed by the SHIRPA protocol. In addition they exhibited a decrease in rotarod performance and locomotor activity. Some behaviours, such as locomotor activity, were also impaired in sham operated animals compared to normal controls, although these impairments were not as marked as those exhibited by the ischaemic mice. This is the first comprehensive analysis of the short term effects of permanent focal ischaemia in mice. In a second series of experiments in the rat, rates of recovery over time were examined. Simple (neurological grades, rotarod) and complex (sticky label test) tasks were examined in rats after middle cerebral artery occlusion up to 7 days post-ischaemia. Ischaemic rats had a profound deficit in contralateral performance on the sticky label task with no evidence of recovery. A less marked deficit was also observed in ipsilateral performance of this task. These deficits were still present 7 days after ischaemia. Ischaemic rats also exhibited a deficit on rotarod performance but this had recovered 7 days post-ischaemia. Thus different sensorimotor tasks have different rates of recovery after focal cerebral ischaemia in the rat. Further characterisation of these tasks will enhance their utility meaningful preclinical means of assessing functional recovery of the administration of potential neuroprotective and regenerative therapies.

Animals↗
PubMed2003

Internal forward models in the cerebellum: fMRI study on grip force and load force coupling.

Internal models are neural mechanisms that can mimic the input-output or output-input properties of the motor apparatus and external objects. Forward internal models predict sensory consequences from efference copies of motor commands. There is growing acceptance of the idea that forward models are important in sensorimotor integration as well as in higher cognitive function, but their anatomical loci and neural mechanisms are still largely unknown. Some of the most convincing evidence that the central nervous system (CNS) makes use of forward models in sensory motor control comes from studies on grip force-load force coupling. We first present a brief review of recent computational and behavioral studies that provide decisive evidence for the utilization of forward models in grip force-load force coupling tasks. Then, we used functional magnetic resonance imaging (fMRI) to measure the brain activity related to this coupling and demonstrate that the cerebellum is the most likely site for forward models to be stored.

Adult↗
PubMedDate not supplied

A numerical grading scale for peripheral nerve function.

A numerical grading scale for median and ulnar function is outlined. This system, based upon the known pathophysiology of chronic nerve compression, creates a hierarchical scale of mutually exclusive categories for motor and sensory function. The scale is responsive to incorporating new technologies for sensorimotor evaluation if these should offer advantages in computer-assisted evaluation, validity, or reliability. The scale is assumed to be nonuniform, and nonparametric statistical analysis, such as use of the Wilcoxon rank-sum test, is appropriate. Where motor function may predominate the peripheral nerve function, such as the ulnar nerve, in contrast to the median nerve, the scale may be uniquely defined to reflect this attribute. Pilot study examples of application of the numerical scoring system are given, and specific areas to better define the scale through research are suggested.

Carpal Tunnel Syndrome↗
PubMed2003

Neural basis for impaired time reproduction in Parkinson's disease: an fMRI study.

Studies involving brain-lesioned subjects have used the paced finger tapping (PFT) task to investigate the neural systems that govern motor timing. Patients with Parkinson's disease (PD), for example, demonstrate abnormal performance on the PFT, characterized by decreased accuracy and variability changes, suggesting that the basal ganglia may play a critical role in motor timing. Consistent with this hypothesis, an fMRI study of healthy participants demonstrated that the medial frontostriatal circuit (dorsal putamen, ventrolateral thalamus, SMA) correlated with explicit time-dependent components of the PFT task. In the current fMRI study, PD patients and healthy age-matched controls were imaged while performing the PFT. PD patients underwent 2 imaging sessions, 1 on and the other off dopamine supplementation. Relative to controls, PD patients were less accurate and showed greater variability on the PFT task relative to controls. No PFT performance differences were observed between the on and off medication states despite significantly greater motor symptoms on the Unified Parkinson's Disease Rating Scale (UPDRS) in the off medication state. Functional imaging results demonstrated decreased activation within the sensorimotor cortex (SMC), cerebellum, and medial premotor system in the PD patients compared to controls. With dopamine replacement, an increase in the spatial extent of activation was observed within the SMC, SMA, and putamen in the PD patients. These results indicate that impaired timing reproduction in PD patients is associated with reduced brain activation within motor and medial premotor circuits. Despite a lack of improvement in PFT performance, PD patient's brain activation patterns were partially "normalized" with dopamine supplementation. These findings could not be attributed to greater head movement artifacts or basal ganglia atrophy within the PD group.

Acoustic Stimulation↗
PubMed2001

Investigation of AM-36: a novel neuroprotective agent.

1. The neurochemical sequelae following cerebral ischaemia are complex, involving excess release of excitatory amino acids, particularly glutamate, disruption of ionic homeostasis due to Na+ and Ca2+ influx and generation of toxic free radicals, ultimately leading to cell death by both necrosis and apoptosis. 2. Drugs that block components of this biochemical cascade, such as glutamate receptor antagonists, sodium channel blockers and free radical scavengers, have been investigated as putative neuroprotective agents. The knowledge that multiple mechanisms contribute to neuronal injury in ischaemia have led to the general recognition that a single drug treatment is unlikely to be beneficial in the treatment of cerebral ischaemia. 3. AM-36 [1-(2-(4-chlorophenyl)-2-hydroxy)ethyl-4-(3,5-bis(1,1-dimethyl)-4-hydroxyphenyl)methylpiperazine] is one of a series of hybrid molecules designed to incorporate multiple neuroprotective mechanisms within the one structure. Primary screening tests demonstrated that AM-36 inhibited binding to the polyamine site of glutamate receptors, blocked neuronal sodium channels and had potent anti-oxidant activity. In neuronal cell cultures, AM-36 inhibited toxicity induced by N-methyl-D-aspartate (NMDA) and the sodium channel opener veratridine and, in addition, inhibited veratridine-induced apoptosis. 4. In a middle cerebral artery occlusion model of stroke in conscious rats, systemic administration of AM-36 markedly reduced both cortical and striatal infarct volume and significantly improved functional outcome in motor performance, neurological deficit and sensorimotor neglect tests. AM-36 was neuroprotective even when administration was delayed until 3 h systemically, or 5 h intravenously, after induction of stroke. 5. These studies indicate that AM-36 is a unique neuroprotective agent with multiple modes of action, making it an attractive candidate for the treatment of acute stroke in humans.

Animals↗
PubMed1996

Interjoint coordination during pointing movements is disrupted in spastic hemiparesis.

Approaches to the rehabilitation of movement in spastic hemiparetic patients depend on knowledge of the underlying mechanisms of movement deficits. The goals of this study were to characterize end-point trajectories and interjoint coordination of arm pointing movements to different targets on a horizontal planar surface and to correlate disruptions in motor control in the affected arm of hemiparetic subjects with the level of spasticity and the degree of functional impairment measured clinically. Arm movements were studied in six normal and 10 hemiparetic subjects. Data from the affected arms of hemiparetic subjects were compared with those from their non-affected arms and to data from the arms of normal subjects. Subjects were seated in front of a horizontal surface adjusted to the height of the sternal notch with the trunk stabilized. They made planar arm reaching movements (20 and 40 cm) to four different targets located directly in front of them and in the ipsilateral and contralateral workspace. Kinematic data from the finger, wrist, elbow and shoulder were recorded with a three-dimensional optical tracking system. Results showed that movement amplitudes were lower and movement times were significantly prolonged in the affected arms. Although trajectories were marked by deviations from smooth straight lines and characterized by increased dispersion and segmentation, even those subjects with the most severe spasticity could reach into all parts of the workspace with both their affected and non-affected arms. This indicated that movement planning in terms of extrapersonal space was unaffected in these subjects. On the other hand, the interjoint coordination of movements made into or out of the typical extensor or flexor synergies was equally disrupted. These findings suggest a bi-level control organization of pointing movements in both normal and hemiparetic subjects: the level of trajectory planning in extrapersonal space and the level specifying interjoint coordination according to the trajectory plan. Deficits in motor performance in stroke patients may be associated with problems at the second control level. This implies some strategies for the rehabilitation of stroke patients with motor disorders. Treatment aimed at improving arm function should be oriented toward restoring the normal sensorimotor relationships between the joints. We also found that while clinical spasticity scores were correlated with some aspects of motor performance, they provided little information about the movement deficit itself.

Adult↗
PubMed2003

Short-lasting impairment of tactile perception by 0.9Hz-rTMS of the sensorimotor cortex.

To test whether low-frequency repetitive transcranial magnetic stimulation (rTMS) of sensorimotor cortex (SM1) has prolonged effects on somatosensory function, eight subjects were given 900 TMS pulses over the left hand SM1 (0.9Hz, 90% of the resting motor threshold) or at sites 3 cm anterior or posterior to it. Tactile threshold of the right hand was increased for a short duration after rTMS over SM1, but two-point discrimination and median nerve SEPs were unaffected after rTMS at any sites.

Adult↗
PubMed2004

Clinical and electrodiagnostic testing of carpal tunnel syndrome: a narrative review.

Carpal Tunnel Syndrome (CTS) is a pressure-induced neuropathy that causes sensorimotor disturbances of the median nerve, which impair functional ability. A clear history that elicits relevant personal and work exposures and the nature of symptoms can lead to a high probability of a correct diagnosis. Hand diagrams and diagnostic questionnaires are available to provide structure to this process. A variety of provocative tests have been described and have variable accuracy. The Phalen's wrist flexion and the carpal compression tests have the highest overall accuracy, while Tinel's nerve percussion test is more specific to axonal damage that may occur as a result of moderate to severe CTS. Sensory evaluation of light touch, vibration, or current perception thresholds can detect early sensory changes, whereas 2-point discrimination changes and thenar atrophy indicate loss of nerve fibers occurring with more severe disease. Electrodiagnosis can encompass a variety of tests and is commonly used to assess the presence/severity of neuropathic changes and to preclude alternative diagnoses that overlap with CTS in presentation. The pathophysiologic changes occurring with different stages of nerve compression must be considered when interpreting diagnostic test results and predicting response to physical therapy management.

Carpal Tunnel Syndrome↗
PubMed1999

Presurgical motor and somatosensory cortex mapping with functional magnetic resonance imaging and positron emission tomography.

OBJECT: Accurate identification of eloquent cortex is important to ensure that resective surgery in the region surrounding the central sulcus is performed with minimum risk of permanent neurological deficit. Functional localization has traditionally been accomplished using intraoperative cortical stimulation (ICS). However, this technique suffers from several disadvantages that make the development and validation of noninvasive methods desirable. Functional localization accomplished by activation studies in which positron emission tomography (PET) scanning and the tracer [15O]H2O have been used has been shown to correlate well with the results of ICS. Another noninvasive method for functional localization is functional magnetic resonance (fMR) imaging. We compared the locations of activation peaks obtained in individual patients using fMR and [15O]H2O PET imaging. METHODS: Twenty-six combined PET activation-fMR imaging studies were performed in 11 patients who were admitted for evaluation before undergoing surgery in the region surrounding the central sulcus. The PET scans were obtained using bolus injections of the cerebral blood flow tracer [15O]H2O (10 mCi). Multislice T2*-weighted gradient-echo echoplanar images were acquired using a 1.5-tesla MR imaging system. Activation maps were aligned with anatomical MR images and transformed into stereotactic space, after which the locations of activation peaks obtained using both modalities were compared. The average distance between activation peaks obtained using fMR imaging and those obtained using PET imaging was 7.9+/-4.8 mm (p>0.05), with 96% of the peaks being located on either the same or adjacent sulci and gyri. Overlapping of voxels activated by each modality occurred in 92% of the studies. Functional MR imaging failed to activate the primary sensorimotor cortex in one study and produced results that were ambiguous in the clinical setting in three cases. CONCLUSIONS: Overall, fMR imaging produced activation that correlated well with that obtained using PET scanning. Discrepancies between the sites of activation identified using these two techniques may reflect differences in their physiological bases.

Brain Diseases↗
PubMedDate not supplied

[Changes in heterogenous neuron populations in the postresuscitation period after heart arrest in rats].

Morphometric examination of neurons of the Vth layer of the sensorimotor cortex and Purkinje's cells in two functionally different parts of the cerebellum was carried out in various periods after resuscitation in rats exposed to 10 or 15-min heart arrest. General regularities and differences in the reaction of heterogenous neuronal populations on ischemia of various duration were detected. The time course of restructuring of the neuronal populations was traced. A relationship between the detected shifts and the rate of neurological resuscitation of the animals was established. Neurons of various compartments of the brain and various types of cells in the heterogenous neuronal populations were found to be characterized by different sensitivity to ischemia.

Animals↗
PubMedDate not supplied

[Effect of polarization of different levels of the visual and motor analyzers on instrumental conditioned reflexes in dogs].

Dogs with stabilized instrumental conditioned reflexes of tonic form to a bell and flickering light, exhibited a depression or complete inhibition of the reflexes after a short anode polarization of the lateral geniculate body (LGB). Polarization of the superior colliculi exerted a similar influence but to a lesser degree. Prolonged polarization of the visual cortex completely inhibited conditioned reflexes to light at the very first or second minute of its action. The degree of inhibition depended on the current intensity, the area of its action and the functional state of the animal. Polarization of the sensorimotor cortex resulted in a delay and often in complete inhibition of the instrumental reflexes. Polarization of the red nucleus also inhibited the reflexes. Evoked potentials recorded from the LGB, the superior colliculi and the visual cortex underwent considerable changes (decrease of the primary response and disappearance of the secondary response) after polarization of the sensorimotor cortex.

Animals↗
PubMed2005

Functional mu opioid receptors are expressed in cholinergic interneurons of the rat dorsal striatum: territorial specificity and diurnal variation.

Striatal cholinergic interneurons play a crucial role in the control of movement as well as in motivational and learning aspects of behaviour. Neuropeptides regulate striatal cholinergic transmission and particularly activation of mu opioid receptor (MOR) inhibits acetylcholine (ACh) release in the dorsal striatum. In the present study we investigated whether this cholinergic transmission could be modulated by an enkephalin/MOR direct process. We show that mRNA and protein of MORs are expressed by cholinergic interneurons in the limbic/prefrontal territory but not by those in the sensorimotor territory of the dorsal striatum. These MORs are functional because potassium-evoked release of ACh from striatal synaptosomes was dose-dependently reduced by a selective MOR agonist, this effect being suppressed by a MOR antagonist. The MOR regulation of cholinergic interneurons presented a diurnal variation. (i) The percentage of cholinergic interneurons containing MORs that was 32% at the beginning of the light period (morning) increased to 80% in the afternoon. (ii) The MOR-mediated inhibition of synaptosomal ACh release was higher in the afternoon than in the morning. (iii) While preproenkephalin mRNA levels remained stable, enkephalin tissue content was the lowest (-32%) in the afternoon when the spontaneous (+35%) and the N-methyl-d-aspartate-evoked (+140%) releases of enkephalin (from microsuperfused slices) were the highest. Therefore, by acting on MORs present on cholinergic interneurons, endogenously released enkephalin reduces ACh release. This direct enkephalin/MOR regulation of cholinergic transmission that operates only in the limbic/prefrontal territory of the dorsal striatum might contribute to information processing in fronto-cortico-basal ganglia circuits.

Acetylcholine↗
PubMed2001

[Clinical applications of functional magnetic resonance imaging].

Despite its immediate success as a tool for basic research, the clinical application of functional MRI(fMRI) is still limited. FMRI has proven useful for presurgical functional mapping of the eloquent cortices. Localization of the sensorimotor cortex by fMRI may be of relatively limited value because the sensorimotor cortex can often be readily localized by means of anatomical methods. In contrast, the language cortices may not be localized anatomically and the language dominant hemisphere has been determined by invasive Wada test. Previous reports have shown that fMRI can be a promising alternative to the Wada test. A recent clinical trial has suggested that fMRI can be used to diagnose Alzheimer's disease in its earliest stage, detecting subclinical deterioration of the memory function. FMRI may be useful to predict the future decline of memory in people with genetic risks. Monitoring of the functional recovery of post-stroke brains may be another promising clinical application of fMRI. FMRI has demonstrated functional reorganization of the brain that may be related to the restoration of motor and language functions.

Brain Diseases↗