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PubMed1992

Electrocortical arousal and spindles on physiological cortico-subcortical interactions.

The neuronal mechanisms of electrocortical arousal and sleep spindles were reviewed on the basis of intracellular analyses on the motor cortex in atraumatically maintained encéphale isolé cat preparations. When arousal is initiated by subcortical afferents from the brainstem, the cortical neurons respond with either excitation (E), inhibition (I), disfacilitation (DF), or disinhibition (DI), in a cascade pattern proceeding from the superficial to deep layers. These neuronal activities on arousal involve DF of the output neurons that may set the subcortical sensorimotor functions in a readiness state for a possible adaptive behavior of animals. This initial transient arousal termed phasic develops soon to the next, more sustained phase termed tonic by the action of other subcortical afferents. The cascade transmissions then occur again, producing E, I, DF, and DI in the cortical neurons but with a reverse laminar pattern proceeding from the deep to superficial layers. These neuronal activities on tonic and arousal deliver the cortical outputs to the subcortical systems that may trigger an orienting or searching behavior of animals in their environment. Sleep spindles also accompany the cascade transmissions that are partly common to those in arousal. Various modes of the cascade transmissions were further examined by applying electric shock stimuli to the cortical surface, the ventrolateral nucleus of the thalamus, and the cerebral peduncle to activate the subcortical afferents converging onto different cortical layers. The combined results from these experiments may imply that the cortico-subcortical interactions in which all the cortical neurons participate with dynamic harmony are instrumental to set a physiological sequence of animal behavior. If these interactions be impaired on the way of normal growth of the brain, as in the case of disorders with the Rett syndrome, many forms of ill adaptation may be brought about by dedifferentiation of sensorimotor functions.

Action Potentials↗

PubMed2002

Cognitive and neuropsychological outcomes: more than IQ scores.

Improved survival in preterm infants has broadened interest in cognitive and neuropsychological outcomes. The incidence of major disabilities (moderate/severe mental retardation, neurosensory disorders, epilepsy, cerebral palsy) has remained consistent, but high prevalence/low severity dysfunctions (learning disabilities, ADHD, borderline mental retardation, specific neuropsychological deficits, behavioral disorders) have increased. The follow-up literature contains methodologic problems that make generalizations regarding outcome difficult, and these are discussed. Although mean IQs of former VLBW infants generally are in the low average range and are 3-9 points below normal birth weight peers, these scores mask subtle deficits in: visual-motor and visual-perceptual abilities, complex language functions, academics (reading, mathematics, spelling and writing), and attentional skills. There is an increased incidence of non-verbal learning disabilities, need for special educational assistance, and behavioral disorders in children born prematurely. Males have more problems, and there is a trend for worsening outcome over time, due to emergence of more subtle deficits in response to increased performance demands. In addition to IQ and achievement testing in follow-up, there should be evaluation of executive functions and attention, language, sensorimotor functions, visuospatial processes, memory and learning, and behavioral adjustment.

Cognition Disorders↗

PubMed1990

Spinal functions in sensorimotor control of movements.

The transformation of sensory information to movement patterns in spinal interneuronal systems is far from just being a stereotyped reflex pattern. Information from the different sensory modalities (skin-, muscle, and joint receptors) is integrated at the interneuronal level and transformed into patterns of coordinated movements which are adapted to the current position and the phase of movement of a limb. In addition, spinal interneuronal systems are capable of generating rhythmic motor activities like locomotion or scratching without a sensory feed-back from the periphery and without a corresponding drive from supraspinal structures. The same interneuronal systems which are engaged in the reflexogenic control and generation of movements at the spinal level also convey information for the performance of supraspinally-induced, goal-directed ("voluntary") movements. The inherent convergence between descending and peripheral afferent information onto common interneuronal systems implies an improved coordination and adaptation of movements in dependence on the peripheral conditions. Disturbance of the supraspinal control of these interneuronal systems leads to an impairment of the transformation of sensory inputs into motor acts. Spasticity is probably partly caused by such a disturbed control of the transmission in the interneuronal systems.

Animals↗

PubMedDate not supplied

Sensorimotor central conduction time in comatose patients.

Motor evoked potentials (MEPs) following magnetic stimulation were recorded in 22 patients comatose as a result of head injury (13 cases), stroke (7 cases) or anoxia (2 cases). Somatosensory evoked potentials (SEPs) from median nerve were recorded as well in 19 cases in the same session. Thirteen patients died or remained vegetative (59.1%), 3 were severely disabled (13.6%) and 6 showed a good recovery (27.3%). MEPs were significantly related to the outcome; they appeared to be a more accurate prognostic indicator than the Glasgow Coma Scale (GCS). However, 1 out of 6 patients with bilaterally absent MEPs (16.7%) showed a good recovery. SEPs were significantly related to the outcome as well, but the combined use of SEP and MEP improved the outcome prediction, decreasing the rate of false negatives. Two patients had normal sensorimotor function, 13 a combined sensorimotor dysfunction, while 4 had a pure motor dysfunction. Our results suggest that SEPs and MEPs may improve the assessment of sensorimotor dysfunction in comatose patients. A significant relationship between MEPs and outcome appears to exist, but the assessment of MEP reliability requires further study.

Adolescent↗

PubMed2006

Epidural cortical stimulation enhances motor function after sensorimotor cortical infarcts in rats.

This study examined whether epidurally delivered cortical electrical stimulation (CS) improves the efficacy of motor rehabilitative training and alters neuronal density and/or cell proliferation in perilesion cortex following ischemic sensorimotor cortex (SMC) lesions. Adult rats were pre-trained on a skilled reaching task and then received partial unilateral SMC lesions and implantation of electrodes over the remaining SMC. Ten to fourteen days later, rats received daily reach training concurrent with anodal or cathodal 100 Hz CS or no stimulation (NoCS) for 18 days. To label newly generated cells, bromodeoxyuridine (BrdU; 50 mg/kg) was administered every third day of training. Both anodal and cathodal CS robustly enhanced reaching performance compared to NoCS controls. Neuronal density in the perilesion cortex was significantly increased in the cathodal CS group compared to the NoCS group. There were no significant group differences in BrdU-labeled cell density in ipsilesional cortex. Staining with Fluoro-Jade-B indicated that neurons continue to degenerate near the infarct at the time when cortical stimulation and rehabilitation were initiated. These data indicate that epidurally delivered CS greatly improves the efficacy of rehabilitative reach training following SMC damage and raise the possibility that cathodal CS may influence neuronal survival in perilesion cortex.

Analysis of Variance↗

PubMed2006

Forebrain D1 function and sensorimotor gating in rats: effects of D1 blockade, frontal lesions and dopamine denervation.

Prefrontal D1 hypoactivity is implicated in the pathophysiology of schizophrenia, and might contribute to sensorimotor gating deficits in schizophrenia patients, based on evidence that D1 blockade in the medial prefrontal cortex (MPFC) reduces prepulse inhibition of startle (PPI) in animal models. PPI is disrupted by systemic and intra-MPFC infusion of the D1 antagonist, SCH23390. We investigated the role of the MPFC in the PPI-disruptive effects of systemic SCH23390 administration, and more generally, in the dopaminergic regulation of PPI. PPI was measured in rats after forebrain manipulations, including systemic administration of SCH23390, ibotenic acid lesions of the MPFC, and 6OHDA-induced dopamine (DA) depletion from MPFC or nucleus accumbens. Systemic SCH23390 disrupted PPI; these effects were not opposed by ibotenic acid lesions of the MPFC. PPI remained intact after MPFC DA depletion, but--as predicted by Bubser and Koch [M. Bubser, M. Koch, Prepulse inhibition of the acoustic startle response of rats is reduced by 6 hydroxydopamine lesions of the medial prefrontal cortex, Psychopharmacology 113 (1994) 487-492]--a reduction in PPI from pre- to post-surgery correlated significantly with MPFC DA loss. The effects of systemic SCH23390 were not opposed by NAC DA depletion. D1 receptors regulate PPI in rats, but this effect does not appear to be mediated either by the MPFC or by increased mesolimbic DA activity.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1997

Mapping of the sensorimotor cortex: functional MR and magnetic source imaging.

PURPOSE: To assess the reliability and comparability of functional MR imaging and magnetic source imaging for mapping the somatosensory cortex. METHODS: Parallel studies were performed in eight volunteer subjects in whom both hemispheres were measured with the use of painless tactile stimulation of the tip of each index finger. Magnetic source imaging was performed using a 37-channel biomagnetometer; evoked magnetic fields were analyzed using the single-equivalent dipole representation to ascertain the neuronal source. Functional MR imaging was performed on a 1.5-T MR unit. Blocks of images during periods of rest and activation were acquired using gradient-echo echo-planar imaging. Correlation analysis identified pixels in which signal intensity correlated with the stimulus function. A subsequent requirement for spatial connectivity of activation was imposed to reduce the random occurrence of pixels satisfying the correlation criteria. RESULTS: Using temporal and spatial statistical criteria for activation, we found that functional MR imaging showed activation in 1 of 16 hemispheres. In three cases, this was accompanied by activity either frontally or ipsilateral to the stimulus. Magnetic source imaging showed parietal contralateral location in all 16 cases. Where successful localization was achieved with both methods, the separation between sources appeared to be between 1 and 4 cm. Functional MR imaging localizations tended to lie more superficially than the magnetic source imaging localizations. Performance of a simple motor task, rather than use of somatosensory stimulation, resulted in a cortical signal change detectable with a similar functional MR imaging approach in all cases, suggesting the more robust nature of this stimulus. CONCLUSIONS: Functional mapping of the somatosensory cortex can be achieved with functional MR imaging or magnetic source imaging. Functional MR imaging yields more spurious locations and fails to show localization more often. If neuronal signal propagation pathways are of interest, the temporal resolution of functional MR imaging alone may be inadequate. A combination of magnetic source imaging and functional MR imaging may allow improved sensitivity, fewer false-positive results, and high spatial and temporal resolution.

Adult↗

PubMed1992

Sensorimotor and cognitive consequences of middle cerebral artery occlusion in rats.

Rats were subjected to either right proximal middle cerebral artery (MCA) occlusion or sham operation, and examined for an extended period on a battery of tests designed to measure simple motor function, sensorimotor integration and cognitive function. Rats with MCA occlusion showed extensive neuronal loss in the dorsolateral striatum and variable neuron loss in the parietal, temporal and frontolateral neocortex. MCA occluded animals exhibited significant impairments in tests of postural reflex, visual and tactile forelimb placing, locomotor coordination, and a test of simultaneous bilateral tactile extinction. The reflex and sensorimotor function deficits recovered to pre-operative levels by Day 30 post-ischemia. Five weeks following surgery, rats were tested in 2 versions of the Morris water task. Rats with MCA occlusion demonstrated significant impairments in their ability to navigate to a hidden platform, but were not significantly impaired on the visible (cued) version of the task. This general pattern of transient sensorimotor and reflex deficits, but with more persistent cognitive impairments, is similar to that seen in humans following MCA infarcts.

Animals↗

PubMed1994

Predictors of nursing home placement and mortality of residents in intermediate care.

Assessments of sensorimotor function, cognitive status and health measures were made in 95 intermediate-care (hostel) residents (mean age 82.7 years). The residents were then followed up for 3 years to determine which measures were associated with nursing-home placement and/or death. Information on the outcome of 92 participants was available at the end of the 3-year period. At this time, 53 residents (58%) were still residing at the hostel, seven (8%) had been transferred to nursing homes and 32 residents (35%) had died. Sixteen of the 32 subjects who had died had been transferred to nursing homes. Discriminant function analysis identified tactile sensitivity, ankle dorsiflexion strength, reaction time, sway with eyes open on a compliant (foam rubber) surface and cognitive impairment as the variables that significantly discriminated between subjects who were still in intermediate care and subjects who had been transferred to nursing homes. This procedure correctly classified 88% of subjects into intermediate care or nursing home groups. These variables, with the exception of ankle dorsiflexion strength, were also included in the final discriminant model when predicting mortality, correctly classifying 71% of the subjects. The findings indicate that cognitive impairment and reduced functioning in a number of sensorimotor factors are strongly related to poor outcomes for residents in hostel care.

Accidental Falls↗

PubMed1990

Experience with the island inferior gluteal thigh flap compared with other local flaps for the reconstruction of the pelvic area.

The pelvic area can be one of the most difficult areas in the body to reconstruct. We divide pelvic wounds into three functional categories: spinal cord injury with no sensation or motor function, spinal cord injury with partial sensorimotor function, and miscellaneous injury, such as that resulting from congenital causes, trauma, or tumor resection. We have found the posterior thigh, particularly the island inferior gluteal thigh flap, to be an excellent choice for all three types of wounds, with the added advantages of sensate coverage and sparing of ambulation musculature in patients for whom such aspects are important. We have found that designing flaps based on the vascular territories of major blood vessels--the angiosome approach described by Taylor and Palmer--provides an excellent and reliable flap for most wounds in the pelvic area. In most patients, the major source vessel is the inferior gluteal artery and the flap is taken as an island flap. When this is not possible or when the island flap does not offer an advantage, we have chosen other local flaps. Our report covers our experience with 36 such procedures in 31 patients, with follow-up ranging from 3 months to 2 years.

Adolescent↗

PubMed2002

Sensorimotor and balance function in older adults with lumbar nerve root compression.

The purpose of this study was to determine how sensorimotor status and balance control would be affected by lumbar nerve root compression in older adults. The vibration sense, joint motion sense, and strength of the lower legs of healthy older adults and older patients with lumbar nerve root compression (n = 17 each group) were tested for sensorimotor function. The motion of the center of pressure during quiet standing, center of pressure during forward reach, and the score on Berg's functional balance test were examined for static, dynamic, and functional balance control abilities, respectively. It was found that the patient group had significantly weaker strength, greater center of pressure motion during quiet stance, slower center of pressure motion, shorter distance during forward reach test, and lower functional balance ability. No significant sensory deterioration was found. Older patients with lumbar nerve root compression had weaker leg muscle strength and poorer balance control than healthy older adults. A thorough examination of strength and balance should be included in the clinical treatment for patients with lumbar nerve root compression.

Age Factors↗

PubMed2004

Cerebral modeling and dynamic Bayesian networks.

The understanding and the prediction of the clinical outcomes of focal or degenerative cerebral lesions, as well as the assessment of rehabilitation procedures, necessitate knowing the cerebral substratum of cognitive or sensorimotor functions. This is achieved by activation studies, where subjects are asked to perform a specific task while data of their brain functioning are obtained through functional neuroimaging techniques. Such studies, as well as animal experiments, have shown that sensorimotor or cognitive functions are the offspring of the activity of large-scale networks of anatomically connected cerebral regions. However, no one-to-one correspondence between activated networks adn functions can be found. Our research aims at understanding how the activation of large-scale networks derives from cerebral information processing mechanisms, which can only explain apparently conflicting activation data. Our work falls at the crossroads of neuroimaging interpretation techniques and computational neuroscience. Since knowledge in cognitive neuroscience is permanently evolving, our research aims more precisely at defining a new modeling formalism and at building a flexible simulator, allowing a quick implementation of the models, for a better interpretation of cerebral functional images. It also aims at providing plausible models, at eht level of large-scale networks, of cerebral information processing mechanisms in humans. In this paper, we propose a formalism, based on dynamic Bayesian networks (DBNs), that respects the following constraints: an oriented, networks architecture, whose nodes (the cerebral structures) can all be different, the implementation of causality--the activation of the structure is caused by upstream nodes' activation--the explicit representation of different time scales (from 1 ms for the cerebral activity to many seconds for a PET scan image acquisition), the representation of cerebral information at the integrated level of neuronal populations, the imprecision of functional neuroimaging data, the nonlinearity and the uncertainty in cerebral mechanisms, and brain's plasticity (learning, reorganization, modulation). One of the main problems, nonlinearity, has been tackled thanks to new extensions of the Kalman filter. The capabilities of the formalism's current version are illustrated by the modeling of a phoneme categorization process, explaining the different cerebral activations in normal and dyslexic subjects.

Bayes Theorem↗

PubMed1989

Stroke rehabilitation: sensorimotor integrative treatment versus functional treatment.

This study compares the effectiveness of two occupational therapy approaches to treating cerebrovascular accident patients--the functional and sensorimotor integrative approaches. Subjects were 90 patients admitted to Holy Family Hospital in Vancouver, Canada, within 12 weeks after a first stroke. Consenting subjects were randomly assigned on admission to one of two occupational therapy treatment groups. All subjects received similar medical and nursing care and physical therapy. An independent clinical evaluator assessed subjects' function in self-care and mobility, meal preparation, and sensorimotor integration at specified times after admission. Neither the evaluator nor the subjects were aware of the treatment group to which they had been assigned. Results showed no statistically significant differences between the two treatment groups on the three outcome measures. We therefore concluded that any differences between the effectiveness of the two approaches are small.

Activities of Daily Living↗

PubMed2006

Vascular endothelial growth factor improves recovery of sensorimotor and cognitive deficits after focal cerebral ischemia in the rat.

Vascular endothelial growth factor (VEGF) is an angiogenesis factor with neurotrophic, neuroprotective and neuroproliferative effects. Depending on the dose, route and time of administration in relation to focal cerebral ischemia, VEGF can improve histological outcome and sensorimotor function in rodents. However, VEGF also increases vascular permeability, which can lead to brain edema and exacerbate ischemic brain injury. Thus, although VEGF is a candidate therapeutic for stroke and other ischemic disorders, its benefit relative to risk is uncertain. Considering that functional rather than histological measures of outcome are probably most relevant to therapeutic prospects for human stroke, we investigated the effects of VEGF after middle cerebral artery occlusion in rats using a series of behavioral tests. We report that VEGF improves functional outcome in ischemic rats, including both sensorimotor and cognitive deficiencies.

Animals↗

PubMedDate not supplied

Muscle strength and mass of lower extremities in relation to functional abilities in elderly adults.

BACKGROUND: Functional and physiological declines in advancing age may be significant limiting factors in reduced physical activity. Sarcopenia of aging, as a normative process or disease, cannot entirely explain reduced physical activity in the elderly. OBJECTIVE: The purpose of the study was to investigate the relationship between muscle loss and reduction in functional abilities in elderly adults and also to determine whether an exercise program can improve functional performance and muscle quality. METHODS: Anthropometric measurements and sensorimotor testing were conducted on 28 volunteers (12 men and 16 women, 82.7 +/- 2.4 years of age) who were permanent residents in a skilled nursing facility. Twenty-nine elderly adults (79.3 +/- 3.5 years of age) served as a control, nonexercising group. Anthropometric measurements included: weight, height, body fat, and thigh circumference. The muscle strength was tested with a medical isokinetic system. We assessed two sensorimotor functions including a 'timed up-and-go' test and a 3-min distance walking test. The institutionalized participants undertook an exercise training program lasting 12 weeks. RESULTS: No significant changes were observed in thigh circumference, body weight, or percentage of body fat in either gender as a result of the exercise training. An improvement in muscle strength was noticed in 82% of the relatively younger group (79-83 years of age) under a slow voluntary contraction at 60 degrees /s (p < 0.05). Post-training results showed a significant improvement in performance in the two sensorimotor tests (p < 0.05). The correlation coefficients between muscle strength and functional ability were weak: r = 0.60 and r = 0. 57 for males and females, respectively. CONCLUSIONS: This study confirmed the positive effects of an exercise program on functional performance in older adults. The improvement in functional abilities did not correlate with muscle strength, body weight, or body fat.

Adipose Tissue↗

PubMed2001

Subunit composition and novel localization of K+ channels in spinal cord.

Axonal K+ channels involved in normal spinal cord function are candidate targets for therapeutics, which improve sensorimotor function in spinal cord injury. To this end, we have investigated the expression, localization, and coassociation of Kv1 alpha and beta subunits in human, rat, and bovine spinal cord. We find that Kv1.1, Kv1.2, and Kvbeta2 form heteromultimeric complexes at juxtaparanodal zones in myelinated fibers. However, these same complexes are also present in paranodal regions of some spinal cord axons, and staining with antibodies against Caspr, a component of the paranodal axoglial junction, overlaps with these paranodal K+ channels. This latter observation suggests a unique role for these channels in normal spinal cord function and may provide an explanation for the sensitivity of spinal cord to K+ channel blockers. Moreover, the conservation of these characteristics between human, rat, and bovine nodes of Ranvier suggests an essential role for this defined channel complex in spinal cord function.

Animals↗

PubMed2000

Early exclusive use of the affected forelimb after moderate transient focal ischemia in rats : functional and anatomic outcome.

BACKGROUND AND PURPOSE: Previous work by researchers in our laboratory has shown that in the rat, the exclusive use of the affected forelimb during an early critical period exaggerates lesion volume and retards functional recovery after electrolytic lesions of the forelimb sensorimotor cortex. In the present study, we examined the effects of exclusive use of the affected forelimb after middle cerebral artery occlusion (MCAO). METHODS: Ischemia of moderate severity was produced in male Long-Evans rats through 45 minutes of occlusion of the left middle cerebral and both common carotid arteries. Exclusive use of either the affected or unaffected forelimb was forced through immobilization of either the ipsilateral (MCAO+ipsi) or contralateral (MCAO+contra) forelimb, respectively, for 10 days in a plaster cast, or the animal was left uncasted (MCAO+nocast). Sham surgeries were performed, and animals were also casted for 10 days or left uncasted. Sensorimotor testing was performed during days 17 to 38. At the end of sensorimotor testing, cognitive performance was tested with use of the Morris water maze. In a separate experiment, temperatures and corticosterone levels were measured during the 10-day period after 45-minute ischemia and casting. RESULTS: The MCAO+ipsi group performed worse on sensorimotor tasks than the MCAO+contra, MCAO+nocast, and sham groups. Infarct volume was significantly larger in the MCAO+ipsi group than in the sham and MCAO+contra groups but not in the MCAO+nocast group. No group differences were found with the Morris water maze, and no group differences were found in either temperature or plasma corticosterone level. CONCLUSIONS: The exclusive use of the affected forelimb immediately after focal ischemia has detrimental effects on sensorimotor function that cannot be attributed to hyperthermia or stress.

Animals↗

PubMed1995

Schizophrenia: a disconnection syndrome?

We review the evidence of pathophysiological changes in the prefrontal and temporal cortices of schizophrenic subjects and of abnormal integration of the physiological dynamics in these two regions. The argument we develop is that some schizophrenic phenomena are best understood in terms of abnormal interactions between different areas, not only at the levels of physiology and functional anatomy, but at the level of cognitive and sensorimotor functioning. We discuss recent functional imaging evidence suggesting abnormal prefronto-temporal interactions in relation to a psychological analysis of experiential symptoms in schizophrenia. Cortico-cortical interactions have been assessed in terms of functional connectivity and eigenimages, using time series of neurophysiological data obtained with positron emission tomography. The results of these analyses suggest that there is a profound disruption of large-scale prefronto-temporal interactions in schizophrenia. These disruptions are particularly relevant if one considers that many positive symptoms of schizophrenia reflect a failure to integrate intrinsically generated behaviour and concurrent perception.

Brain Mapping↗