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LY354740 affects startle responding but not sensorimotor gating or discriminative effects of phencyclidine.

LY354740 ¿(1S,2S,5R,6S)-2-aminobicyclo[3.1.0]hexane-2, 6-dicarboxylate monohydrate¿, a selective group II metabotropic glutamate (mGlu) receptor agonist, was recently reported to attenuate the behavioral effects of phencyclidine (PCP) in rats. In the present study, LY354740 failed to attenuate the discriminative stimulus properties of PCP and its disruption of prepulse inhibition of the acoustic startle response, at a dose range which decreased startle responding. The suggestion that mGlu group II receptor activation induces antipsychotic effects may be premature.

Acoustic Stimulation↗

Autoregressive spectral filter studies on the sensorimotor rhythm EEG state variable.

These studies concern the EEG rhythms of the sensory motor cortex in cats. The cat generates a 12H to 16Hz rhythm related to the MU (Rolandic) rhythm in man. The behavioral state required to generate the rhythm in man and the cat requires complete immobility and alertness. The MU rhythm in man centers around 9Hz and in the cat at 12Hz to 16Hz. This rhythm is used in the biofeedback training for the treatment of intractable seizures in man. It has also been used (12 Hz to 16 Hz) experimentally in animals. It is necessary to enhance the MU rhythm and simultaneously depress the seizure activity. Our interest has been to detect and enhance the SMR rhythm (12 H to 16 Hz) in the cat. We found that when it is enhanced it also enhances the amplitude of auditory evoked potentials in other brain regions.

Algorithms↗

Increased gamma-range activity in human sensorimotor cortex during performance of visuomotor tasks.

OBJECTIVE: We documented changes in spectral power of human electrocorticograms (ECoG) during performance of sensorimotor tasks. METHODS: In 6 human subjects, ECoGs were recorded simultaneously from 14 subdural cortical sites in forearm sensorimotor cortex. The subjects performed 3 visuomotor tasks: tracking a moving visual target with a joystick-controlled cursor, threading pieces of tubing, and pinching the fingers sequentially against the thumb. Control conditions consisted of passive resting and active extension of the wrist. For each site the spectral power of the ECoG during these behaviors was computed for 5 10 Hz ranges between 10 and 60 Hz. RESULTS: All subjects showed power decreases in the range of 11-20 Hz and power increases in the 31-60 Hz range during performance of the visuomotor tasks, at sites in forearm sensorimotor cortex and adjacent areas. Simple wrist movements often produced little change in power. Three subjects showed episodes of explicit gamma oscillations during the visuomotor tasks. Different sites showed increases in gamma-range power for different tasks, indicating that the spatial distribution of the gamma activity is specific to the tasks. Cross-spectra showed that gamma activity could become synchronized between separate sites during particular tasks. CONCLUSIONS: Synchronized gamma-range activity in human sensorimotor cortex increases with performance of manipulative visuomotor tasks, supporting the hypothesis that coherent gamma oscillations may play a role in sensorimotor integration or attention.

Adolescent↗

Central injections of the GABA-transaminase inhibitor ethanolamine-O-sulfate (EOS): effects on brain [14C]2-deoxy-D-glucose uptake and behavior in rats.

Brain glucose utilization was examined 24 h after single intracisternal injections of the GABA-transaminase inhibitor ethanolamine-O-sulfate (EOS) in rats. Qualitative autoradiography indicated a pronounced and homogeneous depression in [14C]2-deoxy-D-glucose ([14C]2DG) uptake throughout the brains of rats treated with 200 or 400 micrograms EOS. Quantitative scintillation counting of 14C in 9 brain areas of other rats confirmed the marked, generalized decrease in label uptake 24 h after EOS. Food intake measurements confirmed previous reports of dose-dependent anorexia after EOS. Rats treated with the 200 micrograms dose showed decreased open-field activity 24 h after injection but no other deficits in various tests of sensorimotor function or in tail-pinch-induced feeding. Rats treated with the 400 micrograms dose also showed deficits in open-field activity, plus deficits in orientation to touch stimuli, longer latencies than controls in catalepsy tests, and faster habituation of startle responses to sound. This group showed normal feeding responses to tail-pinch stimulation in the presence of solid food but not in the presence of liquid food. It was concluded that sensorimotor deficits may play some role in the anorexigenic effects of EOS but are probably not their primary cause. The discrepancy between the apparent degree of depression of brain glucose utilization and the comparatively mild behavioral deficits observed would suggest the possibility that metabolic fuels other than glucose may be mobilized following central EOS treatment.

4-Aminobutyrate Transaminase↗

Effects of implantation site of stem cell grafts on behavioral recovery from stroke damage.

BACKGROUND AND PURPOSE: Findings that MHP36 stem cells grafted into intact parenchyma contralateral to the lesion induced by middle cerebral artery occlusion promoted recovery from stroke deficits led us to investigate whether implantation site of stem cells affects the functional efficacy of MHP36 grafts. METHODS: MHP36 cells (200 000/8 microL) were implanted in the left (n=8) or right (n=9) parenchyma or infused into the right ventricle (intraventricular; n=7) 2 to 3 weeks after stroke induced by 60 minutes of intraluminal right middle cerebral artery occlusion. Additionally, intact (n=11) and stroke (n=7) control groups were tested for 14 weeks in bilateral asymmetry, rotation bias, and spatial learning tasks before histological investigation of cell distribution and differentiation. RESULTS: Rats with left and right parenchymal grafts showed reduced bilateral asymmetry but no improvement in spatial learning. Conversely, spatial learning improved in rats with intraventricular grafts, but marked asymmetry persisted. No grafted group showed reduced amphetamine-induced rotation bias or reduced lesion volume relative to stroke controls. In all grafted groups, cells occupied both sides of the brain. A third of cells grafted in the striatum crossed the midline to occupy homologous regions in intact and lesioned hemispheres and differentiated into site-appropriate phenotypes. CONCLUSIONS: After stroke, both the intact and lesioned hemispheres attract grafted stem cells, suggesting repair processes that utilize cells both for local repair and to augment plastic changes in contralateral motor pathways. However, differential effects of parenchymal and intraventricular grafts suggest that different mechanisms are implicated in recovery from cognitive and sensorimotor deficits induced by stroke.

Animals↗

Extratelencephalic pathways and feeding behavior in the pigeon (Columba livia).

Electrolytic lesions were placed in the tractus septomesencephalicus (TSM) and tractus occipitomesencephalicus (TOM), efferent pathways originating in visual and somatosensorimotor areas of the avian telencephalon and distributing widely to brain stem and spinal nuclear regions. Lesion effects upon several aspects of ingestive behavior were examined using high speed cinematography, operant conditioning procedures and monitoring of intake and feeding responses. While there was no evidence for direct effects upon drinking, both TSM adn TOM lesions were followed by periods of reduced food intake. Disruptions of feeding in TSM birds were mild and relatively transient but birds were hypophagic for prolonged periods. While there were no deficits in the efficiency or accuracy of their feeding responses or their performance in an operant situation, TSM birds displayed an inappropriate seed "sorting" behavior suggestive of lesion effects upon visually controlled food preferences. TOM lesions produced a significant reduction in responsiveness to food (aphagia, hypophagia), impairments in the control of grasping and peck accuracy and a disruption in operant key pecking reinforced by food. These "sensorimotor" and "motivational" deficits were similar to those seen after damage to central trigeminal structures in the pigeon and suggest that TOM is also a component of a putative "feeding system" in the pigeon.

Animals↗

Distribution of dendrites of descending neurons and its implications for the basic organization of the cockroach brain.

To determine precisely the brain areas from which descending neurons (DNs) originate, we examined the distribution of somata and dendrites of DNs in the cockroach brain by retrogradely filling their axons from the cervical connective. At least 235 pairs of somata of DNs were stained, and most of these were grouped into 22 clusters. Their dendrites were distributed in most brain areas, including lateral and medial protocerebra, which are major termination areas of output neurons of the mushroom body, but not in the optic and antennal lobes, the mushroom body, the central complex, or the posteroventral part of the lateral horn. The last area is the termination area of major types of olfactory projection neurons from the antennal lobe, i.e., uni- and macroglomerular projection neurons, so these neurons have no direct connections with DNs. The distribution of axon terminals of ascending neurons overlaps with that of DN dendrites. We propose, based on these findings, that there are numerous parallel processing streams from cephalic sensory areas to thoracic locomotory centers, many of which are via premotor brain areas from which DNs originate. In addition, outputs from the mushroom body, central complex, and posteroventral part of the lateral horn converge on some of the premotor areas, presumably to modulate the activity of some sensorimotor pathways. We propose, based on our results and documented findings, that many parallel processing streams function in various forms of reflexive and relatively stereotyped behaviors, whereas indirect pathways govern some forms of experience-dependent modification of behavior.

Animals↗

Inhibition of morphine tolerance and dependence by diazepam and its relation to the CNS Met-enkephalin levels.

The effect of diazepam on the development of morphine tolerance and dependence was investigated. Male Sprague-Dawley rats were rendered tolerant and dependent by subcutaneous implantation of six morphine pellets. Diazepam (0.025, 0.25 or 2.5 mg/kg body weight) was once daily injected intraperitoneally into rats starting on the first day of implantation. Antinociception was measured by tail-flick (TF) and hot plate (HP) tests, and the extent of sedation determined by a rotarod test before and one hour after diazepam injections everyday for 5 days. Physical dependence on morphine was assessed by an antagonist-precipitated abstinence syndrome on the fifth day of treatment by injecting naloxone 10 mg/kg subcutaneously. Diazepam (0.025-2.5 mg/kg body weight) did not produce significant antinociception or sedation (sensorimotor impairment) in rats implanted with placebo pellets. Diazepam (0.25 and 2.5 mg/kg) inhibited tolerance to TF antinociception in rats implanted with morphine pellets. Sedation as evidenced by sensorimotor impairment induced by morphine pellet implantation was not influenced by diazepam (0.025-2.5 mg/kg). Diazepam administration (0.25 mg/kg) also decreased the degree of jumping behavior observed following naloxone injection in morphine pellet implanted rats. Serum morphine concentration in morphine-diazepam treated rats was not significantly different from that in morphine-saline treated rats. Finally, a decrease in the Met-enkephalin levels observed in the hypothalamus, hippocampus, cortex and spinal cord of morphine dependent rats was reversed by injecting diazepam along with morphine pellet implantation. These results suggest that diazepam inhibits morphine tolerance and dependence, and also prevents morphine-induced decrease in the CNS Met-enkephalin levels in morphine dependent rats.

Animals↗

Reduced expression of the Sp4 gene in mice causes deficits in sensorimotor gating and memory associated with hippocampal vacuolization.

HF-1B/SP4:, a member of the Sp1 family of transcription factors, is expressed restrictively in the developing nervous system and most abundantly in adult hippocampus in mice. Here, we report the generation of hypomorphic Sp4 allele mice, in which the Sp4 deficiency can be rescued by the expression of Cre recombinase. Vacuolization was detected in the hippocampal gray matter of the mutant Sp4-deficient mice. Expression analysis of Sp4 mutant hippocampi revealed an age-dependent decrease in neurotrophin-3 expression in the dentate granule cells. Hypomorphic Sp4 mutant mice displayed robust deficits in both sensorimotor gating and contextual memory. The restoration of Sp4 expression, via a Cre-dependent rescue strategy, completely rescued all the observed molecular, histological and behavioral abnormalities. Our studies thus reveal a novel Sp4 pathway that is essential for hippocampal integrity and modulates behavioral processes relevant to psychiatric disorders.

Age Factors↗

Changes in motor cortex activation after recovery from spinal cord inflammation.

Diseases of the spinal cord are associated with reactive changes in cerebral cortex organization. Many studies in this area have examined spinal cord conditions not associated with recovery, making it difficult to consider the value of these cortical events in the restoration of neurological function. We studied patients with myelitis, a syndrome of transient spinal cord inflammation, in order to probe cortical changes that might contribute to recovery after disease of the spinal cord. Seven patients, each of whom showed improvement in hand motor function after a diagnosis of myelitis involving cervical spinal cord, were clinically evaluated then studied with functional MRI. During right and left index finger tapping, activation volumes were assessed in three cortical motor regions within each hemisphere. Results were compared with findings in nine control subjects. Compared to the control group, myelitis patients had larger activation volumes within contralateral sensorimotor as well as contralateral premotor cortex. The degree of daily hand use showed a significant correlation with the volume of activation in contralateral sensorimotor cortex. Recovery from myelitis is associated with an enlarged activation volume in contralateral motor cortices. This change in motor cortex function is related to behavioral experience, and thus may contribute to motor improvement. The expanded activation in motor cortex, seen with several forms of spinal cord insult may have maximal utility when corticospinal tract axons are preserved.

Adult↗

Distribution of dendrites of descending neurons and its implications for the basic organization of the cockroach brain.

To determine precisely the brain areas from which descending neurons (DNs) originate, we examined the distribution of somata and dendrites of DNs in the cockroach brain by retrogradely filling their axons from the cervical connective. At least 235 pairs of somata of DNs were stained, and most of these were grouped into 22 clusters. Their dendrites were distributed in most brain areas, including lateral and medial protocerebral, which are major termination areas of output neurons of the mushroom body, but not in the optic and antennal lobes, the mushroom body, the central complex, or the posteroventral part of the lateral horn. The last area is the termination area of major types of olfactory projection neurons from the antennal lobe, i.e., uni- and macroglomerular projection neurons, so these neurons have no direct connections with DNs. The distribution of axon terminals of ascending neurons overlaps with that of DN dendrites. We propose, based on these findings, that there are numerous parallel processing streams from cephalic sensory areas to thoracic locomotory centers, many of which are via premotor brain areas from which DNs originate. In addition, outputs from the mushroom body, central complex, and posteroventral part of the lateral horn converge on some of the premotor areas, presumably to modulate the activity of some sensorimotor pathways. We propose, based on our results and documented findings, that many parallel processing streams function in various forms of reflexive and relatively stereotyped behaviors, whereas indirect pathways govern some forms of experience-dependent modification of behavior.

Animals↗

Walking while memorizing: age-related differences in compensatory behavior.

This study investigated predictions of the life-span theory of selection, optimization, and compensation, focusing on different patterns of task priority during dual-task performance in younger and older adults. Cognitive (memorizing) and sensorimotor (walking a narrow track) performance were measured singly, concurrently, and when task difficulty was manipulated. Use of external aids was measured to provide another index of task priority. Before dual-task testing, participants received extensive training with each component task and external aid. Age differences in dual-task costs were greater in memory performance than walking, suggesting that older adults prioritized walking over memory. Further, when given a choice of compensatory external aids to use, older adults optimized walking, whereas younger adults optimized memory performance. The results have broad implications for systemic theories of cognitive and sensorimotor aging, and the costs and benefits of assistive devices and environmental support for older populations.

Adult↗

Differential cyclic AMP dependence of facilitation at Aplysia sensorimotor synapses as a function of prior stimulation: augmentation versus restoration of transmitter release.

Synaptic facilitation at sensory-to-motor neuron synapses in Aplysia is a mechanism contributing to a simple form of learning called behavioral sensitization. Previous work has shown that facilitation is mediated in part by the neurotransmitter 5-HT acting through cAMP to broaden presynaptic action potentials and thus increase transmitter release from the sensory neuron terminals. Other studies have indicated that 5-HT causes facilitation by more than one mechanism, depending on whether the synapse has first been depressed by prior stimulation. The present study examines the involvement of cAMP in facilitation at depressed synapses by utilizing the adenylyl cyclase activator 7 beta-desacetyl-7 beta-[gamma-(N-methylpiperazino)-butyryl] forskolin (7B-forskolin) and 5-HT separately and in combination. Facilitation at relatively rested synapses can be mimicked with application of 7B-forskolin, whereas transmission at synapses that have been subjected to repeated stimulation is not affected. The forskolin derivative by itself increases cAMP levels in sensory neurons and potentiates 5-HT-induced stimulation of cAMP 2-10-fold. Nonetheless, joint application of 7B-forskolin and 5-HT at submaximal concentrations to depressed synapses causes the same amount of facilitation as 5-HT alone. This finding implies that facilitation by 5-HT at repeatedly stimulated synapses is not mediated by cAMP alone. In addition, facilitation by 7B-forskolin at relatively rested synapses can occur without prolongation of action potentials, suggesting that cAMP can act in more than one way to enhance transmission. Taken together with earlier findings, the present results suggest that at least three distinct processes participate in facilitation by 5-HT.

Action Potentials↗

Anti-Nogo-A antibody infusion 24 hours after experimental stroke improved behavioral outcome and corticospinal plasticity in normotensive and spontaneously hypertensive rats.

Nogo-A is a myelin-associated neurite outgrowth inhibitory protein limiting recovery and plasticity after central nervous system injury. In this study, a purified monoclonal anti-Nogo-A antibody (7B12) was evaluated in two rat stroke models with a time-to-treatment of 24 hours after injury. After photothrombotic cortical injury (PCI) and intraventricular infusion of a control mouse immunoglobulin G for 2 weeks, long-term contralateral forepaw function was reduced to about 55% of prelesion performance until the latest time point investigated (9 weeks). Forepaw function was significantly better in the 7B12-treated group 6 to 9 weeks after PCI, and reached about 70% of prelesion levels. Cortical infarcts were also produced in spontaneously hypertensive rats (SHR) by permanent middle cerebral artery occlusion (MCAO). In the control group, forepaw function remained between 40% and 50% of prelesion levels 4 to 12 weeks after MCAO. In contrast, 7B12-treated groups showed significant improvement between 4 and 7 weeks after MCAO from around 40% of prelesion levels at week 4 to about 60% to 70% at 7 to 12 weeks after MCAO. Treatment in both models was efficacious without influencing infarct volume or brain atrophy. Neuroanatomically in the spinal cord, a significant increase of midline crossing corticospinal fibers originating in the unlesioned sensorimotor cortex was found in 7B12-treated groups, reaching 2.3 +/- 1.5% after PCI (control group: 1.1 +/- 0.5%) and 4.5 +/- 2.2% after MCAO in SHR rats (control group: 1.8 +/- 0.8%). Behavioral outcome and the presence of midline crossing fibers in the cervical spinal cord correlated significantly, suggesting a possible contribution of the crossing fibers for forepaw function after PCI and MCAO. The results suggest that specific anti-Nogo-A antibodies bear potential as a new rehabilitative treatment approach for ischemic stroke with a prolonged time-to-treatment window.

Animals↗

Removing zinc from synaptic vesicles does not impair spatial learning, memory, or sensorimotor functions in the mouse.

Zinc-enriched (ZEN) neurons are distributed widely throughout the brain and spinal cord. Synaptic vesicle zinc in these neurons is thought to function as a neuromodulator upon its release into the synaptic cleft. Consistent with this possibility, zinc or zinc chelators can alter spatial learning, working memory, and nociception in rodents. Here we use zinc transporter-3 (ZnT3) knockout mice, which are depleted of synaptic vesicle zinc, to assess the consequences of removing this potential neuromodulator on the behavior of adult mice. ZnT3 knockout mice performed equally as well as wild-type mice in the rotarod, pole, and cagetop tests of motor coordination. They exhibited normal thermal nociception in the hot-plate and tail-flick tests, and had similar olfactory, auditory and sensorimotor gating capabilities as wild-type mice. ZnT3 knockout mice behaved similarly as wild-type mice in the open field test and in the elevated plus maze test of anxiety. They exhibited normal learning and memory in the passive avoidance, Morris water maze, and fear conditioning tasks, and normal working and reference memory in a water version of the radial arm maze. We conclude that synaptic vesicle zinc is not essential for mice to be able to perform these tasks, despite the abundance of ZEN neurons in the relevant regions of the CNS. Either the neuromodulatory effects of zinc are not relevant for the tasks tested here, or mice are able to compensate easily for the absence of synaptic vesicle zinc.

Animals↗

Behavioral effects of psychomotor stimulants in rats with dorsal or ventral subiculum lesions: locomotion, cocaine self-administration, and prepulse inhibition of startle.

Compelling evidence suggests a primary role for the mesoaccumbens dopaminergic pathway in the behavioral effects of amphetamine and cocaine, but the roles of other projections to the accumbens, including those arising in the hippocampal formation, are less clear. The authors evaluated the effects of discrete excitotoxic lesions of either the dorsal or ventral subiculum on the locomotor activating, reinforcing, and sensorimotor gating-disruptive effects of psychomotor stimulant drugs. Whereas dorsal subiculum-lesioned rats were hyperactive in tests of exploratory locomotion and startle reactivity, ventral subiculum-lesioned rats exhibited an attenuated locomotor response to amphetamine, moderately impaired acquisition of cocaine self-administration, and reduced levels of prepulse inhibition of startle. These 2 behavioral profiles overlap considerably with those previously observed in rats with lesions of the rostrodorsal and caudomedial accumbens, respectively, and suggest that projections from dorsal subiculum to accumbens core and ventral subiculum to accumbens shell exert distinct influences on behavioral responses that are amplified by psychomotor stimulant drugs.

Amphetamine↗

Two types of aphagia and two types of sensorimotor impairment after lateral hypothalamic lesions: observations in normal weight, dieted, and fattened rats.

In two experiments, reactions to food and to tactile stimuli were examined in rats whose body weights were normal, reduced by restricted feeding (dieted), or raised by having access to palatable foods (fattened) prior to receiving bilateral lesions in the lateral hypothalamic (LH) area. Postoperative aphagia and sensorimotor impairments were less prolonged than normal in the dieted rats and more prolonged than normal in the fattened rats. The LH lesions produced a transient hyperthermia which was attenuated by dieting and facilitated by fattening. Certain motor impairments (which accompanied more posterior lesion placements), hypokinesia, and a lesion-induced exaggerated aphagia to novel foods were relatively unaffected by preoperative body weight. Depending importantly upon lesion placement, there appeared to be at least two types of aphagia and two types of sensorimotor impairment. Animals with more posterior LH lesions displayed a passive kind of aphagia and sensory neglect. These animals did not react to food or to sensory stimuli presented externally, but they chewed and appeared to swallow food placed in the mouth. Animals with more anterior LH lesions displayed an active kind of aphagia and sensory rejection. These latter animals briskly turned their heads toward food or a light touch; however, they also showed simple stereotyped withdrawal or reactions of aversion to the food, to a light touch, and to a variety of sensory stimuli. Animals with intermediately placed lesions showed symptoms common to passive and active aphagia and to sensory neglect and sensory rejection. The effects of preoperative weight manipulation on the specific types of aphagia and sensorimotor impairments are discussed.

Animals↗

A neuroeconomics approach to inferring utility functions in sensorimotor control.

Making choices is a fundamental aspect of human life. For over a century experimental economists have characterized the decisions people make based on the concept of a utility function. This function increases with increasing desirability of the outcome, and people are assumed to make decisions so as to maximize utility. When utility depends on several variables, indifference curves arise that represent outcomes with identical utility that are therefore equally desirable. Whereas in economics utility is studied in terms of goods and services, the sensorimotor system may also have utility functions defining the desirability of various outcomes. Here, we investigate the indifference curves when subjects experience forces of varying magnitude and duration. Using a two-alternative forced-choice paradigm, in which subjects chose between different magnitude-duration profiles, we inferred the indifference curves and the utility function. Such a utility function defines, for example, whether subjects prefer to lift a 4-kg weight for 30 s or a 1-kg weight for a minute. The measured utility function depends nonlinearly on the force magnitude and duration and was remarkably conserved across subjects. This suggests that the utility function, a central concept in economics, may be applicable to the study of sensorimotor control.

Adult↗