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PubMed2006

Lesions in monkey globus pallidus externus exacerbate parkinsonian symptoms.

To further define the role of the external segment of the globus pallidus (GPe) in the development of parkinsonian motor signs, two rhesus monkeys were made parkinsonian with the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Behavioral assessments of bradykinesia and akinesia as well as single neuron recordings in the internal segment of the globus pallidus (GPi) were performed in both monkeys before and after ablating the sensorimotor portion of GPe. The effects of apomorphine on behavior and neuronal activity were also assessed in the parkinsonian monkeys before and after GPe ablation. We found that lesions in GPe exacerbated parkinsonian symptoms, altered neuronal activity in GPi, and reduced the therapeutic effects of apomorphine. These results support the hypothesis that GPe can influence GPi neuronal activity and is directly involved in parkinsonism. In addition, these data suggest that the inclusion of GPe in pallidotomy lesions for the treatment of Parkinson's disease can block the beneficial effects of antiparkinsonian medications and should be avoided.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1999

Movement-related glutamate levels in rat hippocampus, striatum, and sensorimotor cortex.

Changes in brain extracellular glutamate during movement stress were studied using in vivo microdialysis. Male Long-Evans rats were placed in a clear cylinder designed to elicit behavioral activation while undergoing microdialysis sampling from either the hippocampus, striatum or sensorimotor cortex. Glutamate levels were determined by high performance liquid chromatography with fluorescence detection in the dialysates taken before, during, and after exposure to the cylinder. Animals were in a behaviorally quiescent state before exposure to the cylinder, but they demonstrated increases in rearing, locomotion, and turning while in the cylinder. Dialysate glutamate levels were significantly enhanced in the samples taken while the rat was in the cylinder compared with samples taken before or after exposure to the cylinder. In a second study, rats were implanted with bilateral probes in the forelimb sensorimotor cortex, and one forelimb was immobilized by means of a plaster of paris cast. Glutamate, aspartate, serine, and taurine levels were quantified in casted animals. In casted animals, dialysate glutamate levels were lower on the side contralateral to the immobilized limb during both quiescence and movement stress. Aspartate and taurine, but not serine levels increased during movement stress in both the side contralateral and the side ipsilateral to the immobilized limb. These results suggest that there is extracellular overflow of glutamate and other neuroactive amino acids during spontaneous movement, and chronic disuse can suppress extracellular glutamate levels.

Amino Acids↗
PubMed1989

Interhemispheric transfer in patients with incomplete section of the corpus callosum. Anatomic verification with magnetic resonance imaging.

Tests of interhemispheric disconnection including visual, somesthetic, kinesthetic, auditory, and complex motor functions were performed on seven patients with chronic epilepsy who had undergone partial surgical section of the corpus callosum, verified by magnetic resonance imaging. Two patients with only one third of the splenium remaining demonstrated disconnection syndromes involving all modalities except vision, which was completely intact. Five patients had lesions involving the rostrum and the anterior two thirds to four fifths of the body of the callosum, with the splenium spared. They demonstrated little evidence of disconnection in the modalities indicated, except for left ear suppression on a dichotic listening task and partial somatosensory disruption in some cases. These results emphasize the importance of the posterior corpus callosum for interhemispheric sensory and sensorimotor transfer, although some discrepancies between current behavioral data and previous anatomic findings remain.

Adolescent↗
PubMed2003

Direct input from cochlear root neurons to pontine reticulospinal neurons in albino rat.

The cochlear root neurons (CRNs) are thought to mediate the auditory startle reflex (ASR) in the rat, which is widely used as a behavioral model for the investigation of the sensorimotor integration. CRNs project, among other targets, to the nucleus reticularis pontis caudalis (PnC), a major component of the ASR circuit, but little is known about the organization of this projection. Thus, we injected biotinylated dextran amine (BDA) in CRNs to study their projections with light and electron microscopy. Also, we performed double-labeling experiments, injecting BDA in the CRNs and subunit B of the cholera toxin or Fluorogold in the spinal cord to verify that CRNs project onto reticulospinal neurons. Electron microscopy of the labeled CRNs axons and terminals showed that even their most central and thinnest processes are myelinated. Most of the terminals are axodendritic, with multiple asymmetric synapses, and contain round vesicles (50 nm diameter). Double-labeling experiments demonstrated that CRN terminals are apposed to retrogradely labeled reticulospinal neurons in the contralateral nucleus reticularis PnC and bilaterally in the lateral paragigantocellular nucleus. Analyses of serial sections revealed that multiple CRNs synapse on single reticulospinal neurons in PnC, suggesting a convergence of auditory information. The morphometric features of these neurons classify them as giant neurons. This study confirms that CRNs project directly onto reticulospinal neurons and presents other anatomical features of the CRNs that contribute to a better understanding of the circuitry of the ASR in the rat.

Animals↗
PubMed1984

Correlations among measures of playfulness and skillfulness in captive common marmosets (Callithrix jacchus jacchus).

Infant sensorimotor and social skills, playfulness, and nonplayful behaviors were measured in common marmosets from 6 to 22 weeks old. Different measures of skill showed a low concordance, implying that skill is a multiple rather than unitary attribute. Significant correlations were found between the amount of social play infants performed from 11 to 13 weeks of age and their performance at 14 weeks in (1) competitive food tests with their mothers, and in (2) their ability to negotiate an obstacle for a food reward. Significant correlations were also found between these skills and nonplayful behaviors, however. Comparable analyses at other ages revealed few significant correlations, suggesting that the association between social play and skills is restricted to the age when infants are rapidly becoming independent of their caregivers both for locomotion and food. Age-specific correlations occurred between changes in levels of skills and both playful and nonplay behaviors. Our results are consistent with the hypothesis that social play promotes the development of skills, but alternative explanations are possible.

Animals↗
PubMed2003

[Allocation of cognitive resources during the simultaneous performance of cognitive and sensorimotor tasks].

We review research on the allocation of cognitive resources during the simultaneous performance of cognitive and sensorimotor tasks. From the developmental and clinical perspectives,we emphasize: (1) the distinction between the availability and the allocation of resources, (2) lifespan changes in relation to the environmental validity of sensorimotor functions, and (3) the potentials and limitations for an individuals' adaptations to multi-task constraints. These aspects can be operationalized within the framework of selection, optimization, and compensation (SOC). Related studies focus on older individuals' selective resource allocation and compensatory processes as adaptive means in the context of reduced resources and decreased sensorimotor functioning. Results show that older adults must invest increasing amounts of their cognitive resources into the coordination of bodily functions such as balance and gait. SOC research on Alzheimer's patients provides new insights into the increased risks of falling. We argue that adaptive resource allocation in everyday sensorimotor performance is an instance of intelligent behavior that is insufficiently represented in extant psychometric tests.

Accidental Falls↗
PubMed1982

Dissociation of hunger and self-stimulation by trigeminal deafferentation in the rat.

Section of trigeminal orosensory or oromotor nerves reduces food intake and disrupts performance of a food-reinforced lever pressing response but increases the rate of an identical level pressing response reinforced by electrical stimulation of the lateral hypothalamus. Our findings suggest that trigeminal orosensation plays a critical role in the neural control of hunger in the rat. The results also fail to support a response-oriented theory of intracranial self-stimulation where the latter is thought to involve selective facilitation of sensorimotor circuits underlying species-typical consummatory behavior.

Afferent Pathways↗
PubMed1985

EEG spindle activity as a function of age: relationship to sleep continuity.

This study assessed sleep spindle activity and its relationship to transient EEG activation in young adult and aged cats. Sleep-wake variables were monitored polygraphically for 12 h in 5 young adult (2-4 years) and five aged (9-11 years) animals. Recordings were scored for behavioral state. Then, using bandpass frequency analysis, sensorimotor cortical spindles were evaluated in three, 5-min segments of the NREM sleep EEG. Both the incidence of transient arousals (TA) and spindle (much greater than 25 microV) densities were significantly higher in the aged animals than in the young adults. In the young animals only, spindle densities reliably predicted the incidence of TAs. We suggest that spindle expression varies in relation to ascending reticular activating system tone, constituting a functionally-inhibitory thalamocortical response to neurophysiological conditions which promote central activation.

Adult↗
PubMed1981

Mesencephalic reticular formation stimulation effects on hypothalamic neuronal activity.

The effects of mesencephalic reticular formation (RF) single pulse, 0.5 msec and 0-500 microA, stimulation on lateral preoptic-lateral hypothalamic (LPA-LH) neuronal activity were determined in anesthetized rats. In addition, the effects of LH stimulation on neural activity in the RF and periaqueductal gray (PAG) were evaluated. Recordings from 117 neurons indicate reciprocal connections between the LPA-LH and the mesencephalon. Stimulation of the RF affected 70% of the LPA-LH neurons tested. Short latency decreases in activity predominated indicating an inhibitory synaptic input from the RF to the LPA-LH. Short latency increases in discharge frequency were observed infrequently. Stimulation of the LH affected only 32% of the mesencephalic neurons tested. Short latency decreases in activity were usually observed indicating reciprocal inhibitory synaptic connections between the LPA-LH and the RF and periaqueductal gray. Antidromic responses verified these interconnections and revealed relatively slow conduction velocities of approximately 1.0 m/sec. Results are discussed in terms of the involvement of the LPA-LH and RF in sensorimotor functions, spinal motor excitability, and ingestive behavior.

Action Potentials↗
PubMed2006

Color blindness and contrast perception in cuttlefish (Sepia officinalis) determined by a visual sensorimotor assay.

We tested color perception based upon a robust behavioral response in which cuttlefish (Sepia officinalis) respond to visual stimuli (a black and white checkerboard) with a quantifiable, neurally controlled motor response (a body pattern). In the first experiment, we created 16 checkerboard substrates in which 16 grey shades (from white to black) were paired with one green shade (matched to the maximum absorption wavelength of S. officinalis' sole visual pigment, 492 nm), assuming that one of the grey shades would give a similar achromatic signal to the tested green. In the second experiment, we created a checkerboard using one blue and one yellow shade whose intensities were matched to the cuttlefish's visual system. In both assays it was tested whether cuttlefish would show disruptive coloration on these checkerboards, indicating their ability to distinguish checkers based solely on wavelength (i.e., color). Here, we show clearly that cuttlefish must be color blind, as they showed non-disruptive coloration on the checkerboards whose color intensities were matched to the Sepia visual system, suggesting that the substrates appeared to their eyes as uniform backgrounds. Furthermore, we show that cuttlefish are able to perceive objects in their background that differ in contrast by approximately 15%. This study adds support to previous reports that S. officinalis is color blind, yet the question of how cuttlefish achieve "color-blind camouflage" in chromatically rich environments still remains.

Animals↗
PubMed1997

Insulin-like growth factor-I prevents development of a vincristine neuropathy in mice.

Vincristine is a commonly used antitumor agent whose major dose-limiting side-effect is a mixed sensorimotor neuropathy. To assess whether insulin-like growth factor-I (IGF-I), a neurotrophic agent that supports the survival of motoneurons and enhances regeneration of motor and sensory neurons, could prevent the peripheral neuropathy produced by vincristine, mice were treated with both vincristine (1.7 mg/kg, i.p., 2 x /week) and/or IGF-I (0.3 or 1 mg/kg, s.c. daily) for 10 weeks. In mice treated with vincristine alone, there was evidence of a mixed sensorimotor neuropathy as indicated by changes in behavior, nerve conduction and histology. Caudal nerve conduction velocity was significantly slower in mice treated with vincristine alone as compared with vehicle-treated mice. Vincristine treatment alone also significantly increased hot-plate latencies and reduced gait support and stride length, but not toe spread distances. The effects of vincristine were accompanied by degeneration of sciatic nerve fibers and demyelination, indicating a peripheral neuropathy. IGF-I (1 mg/kg, s.c.) administered to vincristine-treated mice prevented the neurotoxic effects of vincristine as measured by nerve conduction, gait, response to noxious stimuli and nerve histology. At a lower dose of 0.3 mg/kg administered s.c., IGF-I partially ameliorated the neuropathy induced by vincristine as this dose only prevented the change in nerve conduction and hot-plate latencies. IGF-I administered alone had no effect on any of these parameters. These results suggest that IGF-I prevents both motor and sensory components of vincristine neuropathy and may be useful clinically in preventing the neuropathy induced by vincristine treatment.

Animals↗
PubMed2002

Where is 'where' in the human auditory cortex?

We examine the functional characteristics of auditory cortical areas that are sensitive to spatial cues in the human brain, and determine whether they can be dissociated from parietal lobe mechanisms. Three positron emission tomography (PET) experiments were conducted using a speaker array permitting quasi free-field sound presentation within the scanner. Posterior auditory cortex responded to sounds that varied in their spatial distribution, but only when multiple complex stimuli were presented simultaneously, implicating this cortical system in disambiguation of overlapping auditory sources. We also found that the right inferior parietal cortex is specifically recruited in localization tasks, and that its activity predicts behavioral performance, consistent with its involvement in sensorimotor integration and spatial transformation. These findings clarify the functional roles of posterior auditory and parietal cortices, and help to reconcile competing models of auditory cortical organization.

Acoustic Stimulation↗
PubMed2005

Rapid functional recovery after spinal cord injury in young rats.

Responses to traumatic injury in the immature spinal cord may be different from those in adults. We modified an adult model of weight-drop injury to characterize the histopathology and functional recovery after spinal cord injury (SCI) in rat pups at postnatal day 14-15. A 10-g weight was dropped from 2.5 or 5.0 cm at T8-T9. Hindlimb function was evaluated at 24 h and 1, 2, 3, and 4 weeks after injury using the Combined Behavioral Score that estimates overall hind limb sensorimotor function, and the BBB scale for open field locomotion. Histopathology was examined at 15 min, 24 h, and 4 weeks after SCI. The initial hemorrhagic lesion was similar to that seen in adults, but the time course of secondary loss of ventral horn motor neurons was extended. By 4 weeks, only a partial rim of white matter surrounding a central cavity was seen. The 5.0 cm injury group exhibited significantly less recovery of function at 4 weeks than the 2.5 cm group. In the latter, the degree of hindlimb deficit at 4 weeks was similar to that previously described for adults with 10 g x 2.5 cm SCI. However, pups in both injury groups exhibited a significantly faster rate of recovery than adults. Recovery was maximal by 1 week after SCI in pups as compared to 3-4 weeks in adults. The more rapid functional recovery observed in the pups suggests that this new model may be useful for studying mechanisms of functional plasticity after SCI.

Age Factors↗
PubMed1994

Dose-dependent reduction of tissue loss and functional impairment after spinal cord trauma with the AMPA/kainate antagonist NBQX.

Initial studies on the role of glutamate receptors in traumatic spinal cord injury (SCI) implicated the NMDA subclass of ionotropic glutamate receptors in contributing to functional deficits. Recently we obtained evidence suggesting that non-NMDA ionotropic receptors may participate in producing a portion of the behavioral impairment after SCI. To test this hypothesis we have conducted a dose-response experiment, focally injecting 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(f)quinoxaline (NBQX; 1.5, 5, or 15 nmol), a highly selective antagonist of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)/kainate receptors, or vehicle alone, into the injury site beginning at 15 min after a standardized contusive SCI. Behavioral tests of hindlimb reflex and coordinated sensorimotor function were performed 1 d after injury and weekly thereafter. At 4 weeks, spinal cord tissue was examined using quantitative histopathological and immunocytochemical techniques. We found a dose-dependent reduction in tissue loss at the thoracic injury site, with greater residual amounts of both gray matter and myelinated white matter. The maximum dose (15 nmol) significantly reduced the average length of the lesions and doubled the area of residual white matter at the epicenter. Serotonin immunoreactivity caudal to the lesion, used as a marker for descending motor control axons, was also increased in a dose-related manner and nearly tripled with the highest dose of NBQX as compared to controls. Most importantly, the reduced tissue loss in NBQX-treated groups was correlated with reduced functional deficits. There was a dose-dependent enhancement of speed and degree of recovery of both reflex and coordinated hindlimb motor activity, and reduction in the time required for establishing a reflex bladder. The long-term functional deficits at 4 weeks after SCI were reduced in a dose-related manner. Further, regression analyses demonstrated a significant correlation between the increase in amount of residual tissue and improvement in hindlimb function. Our results suggest that in this type of incomplete contusive SCI, a large and functionally important proportion of the tissue loss appears to be due to secondary injury mediated by local AMPA/kainate receptors.

Animals↗
PubMed1994

Tactile discrimination capacity in relation to size and organization of somatic sensory cortex in primates: I. Old-World prosimian, Galago; II. New-World anthropoids, Saimiri and Cebus.

Living primates vary considerably in brain organization, in sensorimotor and cognitive abilities, and in natural behavioral repertoires. Comparative studies of primary (SI) and secondary (SII) somatic sensory cortex of primates reveal major differences in the size and in the complexity of topographic projection patterns. The separate projections of the glabrous hand to SI cytoarchitectonic areas 3b and 1 described in the Old World (OW) anthropoid Macaca and in New World (NW) anthropoids Cebus, Saimiri, and Aotus are lacking in NW Saguinus and in the prosimian Galago. The relationship between the size and complexity of SI organization and tactile abilities is explored in this study of four species of primates--Galago, Macaca, Cebus, and Saimiri. These species were trained to discriminate between pairs of objects differing either in cross-sectional diameter (size) or surface roughness (texture). The course of acquisition of such tactile discrimination in normal Macaca and the nature of deficits following SI or SII removals are known. Selective lesions of either cytoarchitectonic area 1 or 2 in Macaca affect only texture or size discriminations, respectively. Removal of area 3b in SI, or of SII, in Macaca affects both size and texture capacities. The single projection of the glabrous hand to area 3b-1 of Galago led to our expectation that the capacity of Galago to discriminate textures would be more similar to an area 1-lesioned than to a normal Macaca. The substantial and persistent differences between Macaca and Galago on texture, but not size, tasks lend support to the view that the evolution of a second projection of the glabrous hand to area 1 in Macaca contributes to increased texture discrimination capacity. The similarity in multiple projection patterns of the glabrous hand to areas 3b and 1 in Macaca, Saimiri, and Cebus led us to expect greater correspondence in texture discrimination capacity between these three anthropoids than to Galago. Contrary to expectations, Saimiri and Cebus showed a tactile capacity more similar to Galago than to Macaca. Furthermore, the texture discrimination capacity of Cebus actually improved substantially after removal of area 1. This provides further evidence, together with the single SI hand area in NW Saguinus and Galago, that the separate cutaneous projections to area 1 in OW and NW primates are not homologous but evolved independently and possibly serve different tactile functions.

Animals↗
PubMed2005

An investigation of prepulse inhibition in pediatric bipolar disorder.

OBJECTIVES: Deficits in prepulse inhibition (PPI), a measure of sensorimotor gating, have been noted in psychopathologies including schizophrenia and adult bipolar disorder (BPD). Sensorimotor gating deficits may contribute to the emotional and behavioral dysregulation characteristic of pediatric BPD. The current study investigated possible PPI deficits in children with BPD. METHODS: Sixteen children with BPD (medicated, euthymic and non-psychotic) were compared with 13 control subjects on the magnitude of startle habituation, startle-alone response, and inhibition of startle following a 60 or 120-ms prepulse. RESULTS: Both groups displayed startle inhibition by a prepulse, with no significant between-group differences on the magnitude of inhibition after the 60- or 120-ms prepulse. In addition, there were no between-group differences on habituation or baseline startle response. PPI level was not significantly correlated with mood symptoms and did not differ based on comorbid attention deficit hyperactivity disorder. CONCLUSIONS: A lack of PPI deficits in our pediatric bipolar sample contrasts with previous results in adult bipolar and schizophrenic samples. These negative results may reflect the fact that our sample was medicated and was neither acutely manic nor psychotic. Deficits in sensorimotor gating may not be implicated in the emotional and behavioral dysregulation in pediatric BPD.

Adolescent↗
PubMedDate not supplied

Reflection of the systemic mechanisms of instrumental behavior in the activity of brain neurons.

Changes in the impulse activity of neurons of the sensorimotor, parietal associative, and visual areas of the cerebral cortex were studied during the performance of conditioned instrumental alimentary behavior by an animal. Comparative analysis of impulse activity of the neurons investigated showed that 71.4% of the cells of the parietal associative area of the cerebral cortex were activated when the conditional stimulus was turned on; 75.8% of neurons of the visual cortex were activated when the animal pressed the pedal; 82.5% of the cells of the somatosensory and 75.8% of the visual area of the cerebral cortex increased activity upon appearance of milk in the food dispenser. During lapping of the milk, 75.8% of cells of the visual cortex showed reduction of activity. Reorganization of the impulse activity of individual neurons of the cerebral cortex reflected the unfolding of pretriggering integration formed as the result of preliminary training of the animal. The character of the impulse activity of the neurons investigated at the stage of realization of the program of the action and obtaining of reinforcement was determined primarily by the streams of afferent excitations arising during the perception of parameters of the stage-related and final results of the behavior.

Animals↗
PubMed2006

A "sample-and-hold" pulse-counting integrator as a mechanism for graded memory underlying sensorimotor adaptation.

The mechanisms behind the induction of cellular correlates of memory by sensory input and their contribution to meaningful behavioral changes are largely unknown. We previously reported a graded memory in the form of sensorimotor adaptation in the electromotor output of electric fish. Here we show that the mechanism for this adaptation is a synaptically induced long-lasting shift in intrinsic neuronal excitability. This mechanism rapidly integrates hundreds of spikes in a second, or gradually integrates the same number of spikes delivered over tens of minutes. Thus, this mechanism appears immune to frequency-dependent fluctuations in input and operates as a simple pulse counter over a wide range of time scales, enabling it to transduce graded sensory information into a graded memory and a corresponding change in the behavioral output. This adaptation is based on an NMDA receptor-mediated change in intrinsic excitability of the postsynaptic neurons involving the Ca2+-dependent activation of TRP channels.

Acclimatization↗