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At least 1,711 records · Page 95Linked to original sources
PubMed2006

Diabetic Goto-Kakizaki rats display pronounced hyperglycemia and longer-lasting cognitive impairments following ischemia induced by cortical compression.

Hyperglycemia has been shown to worsen the outcome of brain ischemia in several animal models but few experimental studies have investigated impairments in cognition induced by ischemic brain lesions in hyperglycemic animals. The Goto-Kakizaki (GK) rat naturally develops type 2 diabetes characterized by mild hyperglycemia and insulin resistance. We hypothesized that GK rats would display more severe cerebral damage due to hyperglycemia-aggravated brain injury and, accordingly, more severe cognitive impairments. In this study, recovery of motor and cognitive functions of GK and healthy Wistar rats was examined following extradural compression (EC) of the sensorimotor cortex. For this purpose, tests of vestibulomotor function (beam-walking) and combined tests of motor function and learning (locomotor activity from day (D) 1 to D5, operant lever-pressing from D14 to D25) were used. EC consistently reduced cerebral blood flow in both strains. Anesthesia-challenge and EC resulted in pronounced hyperglycemia in GK but not in Wistar rats. Lower beam-walking scores, increased locomotor activity, impairments in long-term habituation and learning of operant lever-pressing were more pronounced and observed at later time-points in GK rats. Fluoro-Jade, a marker of irreversible neuronal degeneration, revealed consistent degeneration in the ipsilateral cortex, hippocampus and thalamus at 2, 7 and 14 days post-compression. The amount of degeneration in these structures was considerably higher in GK rats. Thus, GK rats exhibited marked hyperglycemia during EC, as well as longer-lasting behavioral deficits and increased neurodegeneration during recovery. The GK rat is thus an attractive model for neuropathologic and cognitive studies after ischemic brain injury in hyperglycemic rats.

Animals↗
PubMed1997

Visual-motor transformations required for accurate and kinematically correct saccades.

The goal of this study was to identify and model the three-dimensional (3-D) geometric transformations required for accurate saccades to distant visual targets from arbitrary initial eye positions. In abstract 2-D models, target displacement in space, retinal error (RE), and saccade vectors are trivially interchangeable. However, in real 3-D space, RE is a nontrivial function of objective target displacement and 3-D eye position. To determine the physiological implications of this, a visuomotor "lookup table" was modeled by mapping the horizontal/vertical components of RE onto the corresponding vector components of eye displacement in Listing's plane. This provided the motor error (ME) command for a 3-D displacement-feedback loop. The output of this loop controlled an oculomotor plant that mechanically implemented the position-dependent saccade axis tilts required for Listing's law. This model correctly maintained Listing's law but was unable to correct torsional position deviations from Listing' s plane. Moreover, the model also generated systematic errors in saccade direction (as a function of eye position components orthogonal to RE), predicting errors in final gaze direction of up to 25 degrees in the oculomotor range. Plant modifications could not solve these problems, because the intrisic oculomotor input-output geometry forced a fixed visuomotor mapping to choose between either accuracy or Listing's law. This was reflected internally by a sensorimotor divergence between input-defined visual displacement signals (inherently 2-D and defined in reference to the eye) and output-defined motor displacement signals (inherently 3-D and defined in reference to the head). These problems were solved by rotating RE by estimated 3-D eye position (i.e., a reference frame transformation), inputting the result into a 2-D-to-3-D "Listing's law operator," and then finally subtracting initial 3-D eye position to yield the correct ME. This model was accurate and upheld Listing's law from all initial positions. Moreover, it suggested specific experiments to invasively distinguish visual and motor displacement codes, predicting a systematic position dependence in the directional tuning of RE versus a fixed-vector tuning in ME. We conclude that visual and motor displacement spaces are geometrically distinct such that a fixed visual-motor mapping will produce systematic and measurable behavioral errors. To avoid these errors, the brain would need to implement both a 3-D position-dependent reference frame transformation and nontrivial 2-D-to-3-D transformation. Furthermore, our simulations provide new experimental paradigms to invasively identify the physiological progression of these spatial transformations by reexamining the position-dependent geometry of displacement code directions in the superior colliculus, cerebellum, and various cortical visuomotor areas.

Animals↗
PubMedDate not supplied

Influence of extirpation of the sensorimotor area of the cortex on the formation of conditioned reflexes in response to a complex signal in the ontogenesis of the cat.

The influence of the extirpation of the sensorimotor cortex (SMC) on the formation and maintenance of a previously developed alimentary conditioned reflex to a simultaneous complex stimulus (light + sound) with extinction of the reaction to unreinforced components of the complex signal was studied in kittens aged 39 days to 4 months. The extirpation of the SMC prior to 2.5 months of age had no influence on either the formation or maintenance of the conditioned reflex to the complex signal developed prior to the operation. The extirpation of the SMC in preliminarily trained kittens aged 3.5 months and older leads to disinhibition of the differential components when the positive conditioned reflex to the complex signal is maintained. In untrained kittens of the same age the extirpation of the SMC was manifested in the animals' incapacity to inhibit the motoric reaction to the differential signal. The question of the role of the SMC in ontogenesis during the formation of adequate forms of behavior which require the achievement of intersensory interactions is discussed.

Acoustic Stimulation↗
PubMed2005

Partial reversal of phencyclidine-induced impairment of prepulse inhibition by secretin.

BACKGROUND: Secretin is a "gut-brain" peptide whose neural function is as yet poorly understood. Several clinical studies have reported modestly increased social interaction in autistic children following intravenous secretin administration. Very recently secretin also was administered to schizophrenic patients and found to increase social interaction in some individuals. METHODS: In light of this finding, we assessed the ability of secretin to reverse phencyclidine- (PCP) induced impairment in prepulse inhibition (PPI), a leading animal model of sensorimotor gating deficits in schizophrenia. RESULTS: Similar to atypical antipsychotics, secretin (1, 3, 10, 30, and 100 microg/kg) partially and dose-dependently reversed the PCP-induced deficit in PPI without significantly affecting baseline startle when administered intraperitoneally (IP) 10 minutes following IP administration of PCP (3 mg/kg). CONCLUSIONS: This finding may be relevant to observations of antipsychotic efficacy of secretin in schizophrenic patients as well as our previous report that systemically administered secretin is capable of modulating conditioned fear, even at quite low doses.

Acoustic Stimulation↗
PubMed1996

Enzyme-histochemical and morphological characteristics of fast- and slow-twitch skeletal muscle after brain infarction in the rat.

The right middle cerebral artery was permanently occluded in 12-week-old male spontaneously hypertensive rats. After the surgery the rats were subjected to repeated behavioural tests during the observation period. Fourteen weeks after surgery the fast-twitch extensor digitorum longus (EDL) and the slow-twitch soleus muscle of both sides were removed and examined with regard to muscle fibre characteristics obtained by histochemical and morphometrical methods. Comparisons were made with age-matched controls. Limb placement and the ability to traverse a beam or a rotating pole were repeatedly tested 2-13 weeks after the operation. In spite of permanent sensorimotor deficits in limb placement and when traversing a rotating pole or beam, no increase in pathological changes was noted in either EDL or soleus. The number and proportion of fibre types remained unchanged in both muscles. There was no difference in muscle fibre size in either EDL or soleus. It is concluded that brain infarction in the rat, although causing marked impairment of contralateral motor function, does not have a major influence on the muscle-fibre morphology or fibre-type composition, irrespective of muscle type.

Animals↗
PubMed2003

Relationships between various behavioural abnormalities and nigrostriatal dopamine depletion in the unilateral 6-OHDA-lesioned rat.

While rotational asymmetry is used as a characteristic behavioural sign of striatal dopamine (DA) loss in unilateral animal models of Parkinson's disease (PD), there is relatively little analysis of how other common behavioural deficits relate to nigrostriatal DA depletion. We analysed the relationships between several deficits induced by unilateral 6-OHDA lesions and striatal neurochemistry, as well as neuronal loss in the dopaminergic substantia nigra (SN). Behaviour was evaluated from before until 6 weeks after surgery and abnormalities appeared in body axis, head position and sensorimotor performance as well as apomorphine-induced rotation. As expected, rotational behaviour correlated with striatal DA loss and not with other striatal neurotransmitters measured. Similar observations were found for sensorimotor deficits ('disengage task'). Both deficits were observed in rats with >70% loss of TH+ nigral neurons and >80% loss of striatal DA. Additional postural abnormalities appeared with mean losses of 87% of nigral DA neurons and 97% striatal DA, consistent with observations in patients with advanced PD. The data show that the repertoire of behavioural abnormalities manifested by hemiparkinsonian rats relate directly to the degree of nigrostriatal DA loss and, therefore, mimic features of PD. Analysis of such behaviours are relevant for chronic therapeutic studies targeting PD.

Animals↗
PubMed1999

The gene encoding proline dehydrogenase modulates sensorimotor gating in mice.

Hemizygous cryptic deletions of the q11 band of human chromosome 22 have been associated with a number of psychiatric and behavioural phenotypes, including schizophrenia. Here we report the isolation and characterization of PRODH, a human homologue of Drosophila melanogaster sluggish-A (slgA), which encodes proline dehydrogenase responsible for the behavioural phenotype of the slgA mutant. PRODH is localized at chromosome 22q11 in a region deleted in some psychiatric patients. We also isolated the mouse homologue of slgA (Prodh), identified a mutation in this gene in the Pro/Re hyperprolinaemic mouse strain and found that these mice have a deficit in sensorimotor gating accompanied by regional neurochemical alterations in the brain. Sensorimotor gating is a neural filtering process that allows attention to be focused on a given stimulus, and is affected in patients with neuropsychiatric disorders. Furthermore, several lines of evidence suggest that proline may serve as a modulator of synaptic transmission in the mammalian brain. Our observations, in conjunction with the chromosomal location of PRODH, suggest a potential involvement of this gene in the 22q11-associated psychiatric and behavioural phenotypes.

Acoustic Stimulation↗
PubMed2003

Efficiency of grip force adjustments for impulsive loading during imposed and actively produced collisions.

During object manipulation, both predictive feedforward and reactive feedback mechanisms are available to adjust grip force (GF) levels to compensate for the destabilizing effects of load force changes. During collisions, load force increases impulsively (< 20 ms). Thus, only predictive control of GF can be used to ensure grasp stabilization. A collision paradigm is here used to investigate the effects of practice and vision on the efficiency of the predictive control of GF. Subjects actively produced or received an imposed collision with a pendulum. Subjects were more efficient (used smaller GF for identical loads) when producing than when receiving the collisions. Effects of practice were evident in the active producing task only, with GF levels reducing over repetitions, suggesting that sensorimotor memory for the task was used to adjust GF more efficiently. With imposed collisions, GF levels did not reduce with repetition, which suggests that a direct relation between motor action and sensory feedback may be necessary to improve efficiency. Nevertheless, in this condition GF was lower with visual feedback, indicating potential for more efficient grip possibly associated with subjects degree of confidence. We discuss the implications of these results for accounts of the predictive and the reactive control of movement.

Adaptation, Physiological↗
PubMed2005

Skull fracture during infancy: a five-year follow-up.

A group of 19 children, who had received a skull fracture during infancy, were assessed at least 5 years following injury. The majority of the group (89%) had received a mild traumatic brain injury (TBI), with the remaining two (11%) having a moderate injury. The neuropsychological, academic, and psychosocial functioning of the TBI group was compared to that of 20 orthopedic subjects. The two groups were matched on the variables of gender, age, and socio-economic status. The TBI group was impaired on tests of visual attention and memory for faces. The two groups did not differ significantly on measures of language, sensorimotor functions, or visuospatial functioning. There were no statistically significant differences between the two groups on academic performance, or parent and teacher reports of psychosocial functioning. It is concluded that while there is an absence of deficits in the vast majority of functions, skull fracture in infancy can result in enduring impairment in specific cognitive skills related to the processing of complex nonverbal stimuli.

Attention↗
PubMed2004

Temporal sparseness of the premotor drive is important for rapid learning in a neural network model of birdsong.

Sparse neural codes have been widely observed in cortical sensory and motor areas. A striking example of sparse temporal coding is in the song-related premotor area high vocal center (HVC) of songbirds: The motor neurons innervating avian vocal muscles are driven by premotor nucleus robustus archistriatalis (RA), which is in turn driven by nucleus HVC. Recent experiments reveal that RA-projecting HVC neurons fire just one burst per song motif. However, the function of this remarkable temporal sparseness has remained unclear. Because birdsong is a clear example of a learned complex motor behavior, we explore in a neural network model with the help of numerical and analytical techniques the possible role of sparse premotor neural codes in song-related motor learning. In numerical simulations with nonlinear neurons, as HVC activity is made progressively less sparse, the minimum learning time increases significantly. Heuristically, this slowdown arises from increasing interference in the weight updates for different synapses. If activity in HVC is sparse, synaptic interference is reduced, and is minimized if each synapse from HVC to RA is used only once in the motif, which is the situation observed experimentally. Our numerical results are corroborated by a theoretical analysis of learning in linear networks, for which we derive a relationship between sparse activity, synaptic interference, and learning time. If songbirds acquire their songs under significant pressure to learn quickly, this study predicts that HVC activity, currently measured only in adults, should also be sparse during the sensorimotor phase in the juvenile bird. We discuss the relevance of these results, linking sparse codes and learning speed, to other multilayered sensory and motor systems.

Algorithms↗
PubMed1981

Sensorimotor performance and limb preference.

The purpose of the study was to examine simple and choice fractionated reaction time components with respect to limb preference. Subjects (10 males, 10 females) participated in two experiments. The first experiment involved sensorimotor performance of the hands under four conditions of preferred only, nonpreferred only, bilateral simultaneous, and choice handgrip reaction time. The second experiment involved preferred and nonpreferred knee extension under the same conditions. Simple RT results indicated that performance task measures differed only for the preferred bilateral hand RT and corresponding premotor time. Under choice situations, the most rapid scores occurred with preferred unilateral reaction times due to briefer premotor times. The influence of the central, premotor component relative to simple and choice performance is discussed. Results are also presented with respect to male and female differences.

Adult↗
PubMed2005

Brief intermittent access to sucrose differentially modulates prepulse inhibition and acoustic startle response in obese CCK-1 receptor deficient rats.

Otsuka Long-Evans Tokushima Fatty (OLETF) rats lack the CCK-1 receptor and are hyperphagic and obese. CCK-1 receptors play a role in prepulse inhibition (PPI) by modulating mesolimbic dopamine transmission, a modulator of sensorimotor gating. Therefore, the present study assessed the effects of brief, daily sucrose access on PPI and acoustic startle response (ASR) in OLETF rat and age-matched non-mutant Long-Evans Tokushima Otsuka (LETO) rats. The results revealed that OLETF rats with sucrose access showed an increased ASR [F(1,16) = 6.84; P < 0.01)], relative to sucrose receiving LETO rats. No significant sucrose effect (P = 0.283) on PPI was noted in OLETF rats, whereas sucrose receiving LETO rats had a significantly lower (P < 0.05) PPI percentage than non-sucrose controls. In contrast, sucrose-receiving OLETF rats expressed significantly higher PPI percentage than LETO rats with identical sucrose presentation (P < 0.01). Taken together, these results suggest that sucrose access alters PPI and ASR in general, and the CCK-1 receptors play a modulatory role in facilitating or inhibiting these responses, respectively. A similar effect may be contributory to the hyperphagic behavioral phenotype of obese animal models with altered central dopamine regulation.

Acoustic Stimulation↗
PubMed2005

Erythropoietin improves functional and histological outcome in neonatal stroke.

Neonatal stroke is a condition that leads to disability in later life, and as yet there is no effective treatment. Recently, erythropoietin (EPO) has been shown to be cytoprotective following brain injury and may promote neurogenesis. However, the effect of EPO on functional outcome and on morphologic changes in neonatal subventricular zone (SVZ) following experimental neonatal stroke has not been described. We used a transient focal model of neonatal stroke in P10 rat. Injury was documented by diffusion weighted MRI during occlusion. Immediately upon reperfusion, either EPO (5U/gm) or vehicle was administered intraperitoneally and animals were allowed to grow for 2 wk. Sensorimotor function was assessed using the cylinder rearing test and then brains were processed for volumetric analysis of the SVZ. Stroke induced SVZ expansion proportional to hemispheric volume loss. EPO treatment markedly preserved hemispheric volume and decreased the expansion of SVZ unilaterally. Furthermore, EPO treatment significantly improved the asymmetry of forelimb use following neonatal stroke. This functional improvement directly correlated with the amount of preserved hemispheric volume. These results suggest EPO may be a candidate in the treatment of neonatal stroke.

Animals↗
PubMedDate not supplied

[The neuronal reaction of the sensorimotor cortex to stimulation of the lateral hypothalamus with a background of the microiontophoretic administration of tetragastrin and bradykinin: the role of food reinforcement].

Reactions of neurons of sensorimotor cortex to stimulation of the "center of hunger" in the lateral hypothalamus were studied at the background of microiontophoretic application of gastrin, and bradikinin in satiated freely behaving rabbits under conditions of presence or absence of free access to food. It was shown that food reinforcement essentially changed reactions of neurons to electrical stimulation of the lateral hypothalamus at the background of application of neuropeptides under study. This probably led to specific reorganization in the neuronal system which underlay the mechanism of interaction between motivation and reinforcement influences on the neurons.

Animals↗
PubMed2006

Profile of immediate early gene expression in the lumbar spinal cord of low-thoracic paraplegic mice.

Induction of immediate early gene (IEG) expression is believed to constitute one of the earliest steps in plasticity and long-term modification of neuronal properties. Although behavioral evidence of neuronal plasticity at the sublesional level after spinal cord injury exists, spatiotemporal changes of IEGs in spinal segments located caudally to such an injury have never been examined. Here, the authors studied spatiotemporal changes of c-fos, nor-1, nur77, nurr1, and retinoid x receptor (rxr) messenger RNA expression in the lumbar segments L1-L2 after low-thoracic spinal transection (Tx). C-fos expression generally increased in the dorsal horn with significant levels reached at 3 days and 14 days post-Tx. Basal nor-1 transcript levels decreased in the intermediate zone and dorsal horn areas at 7 days. Nur77 levels were nonsignificantly depressed throughout that period of time, whereas nurr1 and rxr transcripts were not detected before or after Tx. In conclusion, the results provide evidence of distinct roles for c-fos and nor-1 in reorganization and plasticity of neuronal networks typically involved in sensorimotor integration and locomotor control.

Animals↗
PubMed2002

The long-term resetting of a brainstem pacemaker nucleus by synaptic input: a model for sensorimotor adaptation.

The cellular mechanisms behind sensorimotor adaptations, such as the adaptation to a sustained change in visual inputs by prism goggles in humans, are not known. Here we present a novel example of long-term sensorimotor adaptation in a well known neuroethological model, the jamming-avoidance response of a weakly electric fish. The adaptation is relatively long lasting, up to 9 hr in vivo, and is likely to be mediated by NMDA receptors. We demonstrate in a brain slice preparation that the pacemaker nucleus is the locus of adaptation and that it responds to long-lasting synaptic stimulation with an increase in the postsynaptic spike frequency persisting for hours after stimulus termination. The mechanism for the neuronal memory behaves as an integrator, and memory duration and strength are quantitatively related to the estimated amount of synaptic stimulation. This finding is contrary to the idea that neurons respond solely to long-lasting synaptic input by turning down their intrinsic excitability. We show that this positive feedback at the cellular level actually contributes to a negative feedback loop at the organismic level if the entire neural circuit and the behavioral link are considered.

Action Potentials↗
PubMed2002

Brain activation and sexual arousal in healthy, heterosexual males.

Despite the brain's central role in sexual function, little is known about relationships between brain activation and sexual response. In this study, we employed functional MRI (fMRI) to examine relationships between brain activation and sexual arousal in a group of young, healthy, heterosexual males. Each subject was exposed to two sequences of video material consisting of explicitly erotic (E), relaxing (R) and sports (S) segments in an unpredictable order. Data on penile turgidity was collected using a custom-built pneumatic pressure cuff. Both traditional block analyses using contrasts between sexually arousing and non-arousing video clips and a regression using penile turgidity as the covariate of interest were performed. In both types of analyses, contrast images were computed for each subject and these images were subsequently used in a random effects analysis. Strong activations specifically associated with penile turgidity were observed in the right subinsular region including the claustrum, left caudate and putamen, right middle occipital/ middle temporal gyri, bilateral cingulate gyrus and right sensorimotor and pre-motor regions. Smaller, but significant activation was observed in the right hypothalamus. Few significant activations were found in the block analyses. Implications of the findings are discussed. Our study demonstrates the feasibility of examining brain activation/sexual response relationships in an fMRI environment and reveals a number of brain structures whose activation is time-locked to sexual arousal.

Adolescent↗
PubMed1976

Planning infant learning programs.

Based on a review of the literature, a theoretical basis for planning learning programs for infants is presented. The prerequisites for effective programming include attention to the characteristics of the learning environment, the infant or learner, and the stimulus-response mechanism. The goals of such a program include provision of sensorimotor experience and promotion of infant attachment to a mother or mother-surrogate as a basis for establishing a sense of security and competency in the infant. The parent must be taught to recognize the infant's best periods of alertness, develop sensitivity to the infant's signals, and utilize appropriate stimulation routines in interactive patterns in order to create an environment most conducive to cognitive development. Specific program content may be varied within the theoretical framework to fit the needs of special children and their families.

Attention Deficit Disorder with Hyperactivity↗