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At least 487 records · Page 27Linked to original sources
PubMed1997

Effects of transcutaneous electrical nerve stimulation on memory and affective behavior in a stroke patient.

Although stroke is characterized by both a loss of mental and sensorimotor abilities, rehabilitation is particularly aimed at recovery from physical disabilities. In the case study reported in this article, it was hypothesized that a 30-min-a-day treatment with transcutaneous electrical nerve stimulation (TENS) might improve memory and affective behavior in a stroke patient. The hypothesis was derived from animal experimental studies in which peripheral stimulation resulted in activation of the hippocampus and hypothalamus. Although treatment could be started only 6 months after onset, the results suggest that TENS has a beneficial influence on visual short-term memory, verbal long-term memory, and verbal fluency. Moreover, [he patient's independent and social functioning in daily life improved. The conflicting effects of TENS on the patient's affective behavior are discussed.

Journal Article↗
PubMed2006

Target-specific regulation of synaptic efficacy in the feeding central pattern generator of Aplysia: potential substrates for behavioral plasticity?

The contributions to this symposium are unified by their focus on the role of synaptic plasticity in sensorimotor learning. Synaptic plasticities are also known to operate within the central pattern generator (CPG) circuits that produce repetitive motor programs, where their relation to adaptive behavior is less well understood. This study examined divergent synaptic plasticity in the signaling of an influential interneuron, B20, located within the CPG that controls consummatory feeding-related behaviors in Aplysia. Previously, B20 was shown to contain markers for catecholamines and GABA (Díaz-Ríos et al., 2002), and its rapid synaptic signaling to two follower motor neurons, B16 and B8, was found to be mediated by dopamine (Díaz-Ríos and Miller, 2005). In this investigation, two incremental forms of increased synaptic efficacy, facilitation and summation, were both greater in the signaling from B20 to B8 than in the signaling from B20 to B16. Manipulation of the membrane potentials of the two postsynaptic motor neurons did not affect facilitation of excitatory postsynaptic potentials (EPSPs) to either follower cell. Striking levels of summation in B8, however, were eliminated at hyperpolarized membrane potentials and could be attributed to distinctive membrane properties of this postsynaptic cell. GABA and the GABAB agonist baclofen increased facilitation and summation of EPSPs from B20 to B8, but not to B16. The enhanced facilitation was not affected when the membrane potential of B8 was pre-set to hyperpolarized levels, but GABAergic effects on summation were eliminated by this manipulation. These observations demonstrate a target-specific amplification of synaptic efficacy that can contribute to channeling the flow of divergent information from an intrinsic interneuron within the buccal CPG. They further suggest that GABA, acting as a cotransmitter in B20, could induce coordinated and target-specific pre- and postsynaptic modulation of these signals. Finally, we speculate that target-specific plasticity and its modulation could be efficient, specific, and flexible substrates for learning-related modifications of CPG function.

Animals↗
PubMed1992

Hyperactivity, hyper-reactivity, and sensorimotor deficits induced by low doses of the N-methyl-D-aspartate non-competitive channel blocker MK801.

Three doses of MK801 (0.05 mg/kg, 0.3 mg/kg and 1.0 mg/kg) were given systemically to adult male rats, which were then tested on a battery of previously learned, reactive and spontaneous behaviors. Hyperactivity, hyper-reactivity, reductions in rearing behavior and deficits in tongue extension were found at the 0.05 mg/kg dose. Similar, but more severe results were found at the 0.3 mg/kg dose, with the addition of difficulties in climbing, balancing on a beam, and abnormalities in orienting to tactile stimuli. A number of tasks could not be performed at the 1.0 mg/kg dose including tongue extension, orienting, balancing on a beam, and climbing. Additionally, abnormal postures, gaits, and swimming behaviors were observed at this dose. These results characterize the behavioral effects of MK801 as a syndrome of hyperactivity, hyper-reactivity, and sensorimotor deficits. Evidence of this syndrome was present at all three doses, including the 0.05 mg/kg dose, which previously has been claimed to induce deficits similar to hippocampal lesions. Learning literature employing MK801 is discussed in the context of the behavioral deficits found in this study.

Animals↗
PubMed2005

Recovery of impaired songs following unilateral but not bilateral lesions of nucleus uvaeformis of adult zebra finches.

Zebra finches utilize neural circuits in both cerebral hemispheres to produce their learned songs. Although direct reciprocal connections do not exist between song control nuclei across hemispheres, premotor activity in these nuclei during singing is precisely and continuously coordinated between the hemispheres. We hypothesized that this interhemispheric coordination is mediated by bilateral feedback projections from medullary and midbrain song control nuclei to the thalamic song control nucleus uvaeformis (Uva). Consistent with our hypothesis, bilateral lesions of Uva severely impaired singing. This impairment was long-lasting, as it persisted for at least 35 days after the lesions. Unilateral lesions of Uva on either side also resulted in an immediate singing impairment. However, song recovered substantially after less than 15 days, suggesting a possible compensation by the unlesioned side. Although the acoustic structure of individual syllables recovered fully after unilateral lesioning, subtle changes in the sequencing of syllables were observed after song recovery, suggesting that the lesion led to an alteration in the functioning of the remaining song control network. These results demonstrate that the adult songbird brain can adjust to damage to certain parts of the song control network and recover from their associated singing deficits. The well-identified and localized central neural pathways mediating birdsong production provide an advantageous model system to analyze systematically the sensorimotor contexts and the specific sites and mechanisms for behavioral recovery following partial damage to a behavior-producing neural circuit.

Animals↗
PubMed2002

L-DOPA-induced dyskinesia in the intrastriatal 6-hydroxydopamine model of parkinson's disease: relation to motor and cellular parameters of nigrostriatal function.

In order to assess the role of striatal dopamine (DA) afferents in L-DOPA-induced dyskinesia, we have studied a large series of rats sustaining 2, 3, or 4 unilateral injections of 6-hydroxydopamine (6-OHDA) in the lateral striatum. This type of lesion produced a dose-dependent depletion of DA fibers in the caudate-putamen, which was most pronounced in the lateral aspects of this structure. An additional group of rats was injected with 6-OHDA in the medial forebrain bundle to obtain complete DA denervation on one side of the brain. During a course of chronic L-DOPA treatment, rats with intrastriatal 6-OHDA lesions developed abnormal involuntary movements (AIMs), which mapped onto striatal domains exhibiting at least approximately 90% denervation, as judged by DA transporter autoradiography. The denervated areas showed local upregulation of preproenkephalin and prodynorphin mRNA, and FosB-like immunoreactivity, which were highly correlated with the rats' AIM scores. When compared to completely DA-denervated animals, the rats with intrastriatal 6-OHDA lesions showed an overall lower incidence, lower severity and different topographic distribution of AIMs. The involvement of proximal limb and axial muscles in the abnormal movements was proportional to the spreading of the lesion from lateral towards medial aspects of the caudate-putamen. Locomotive AIMs were only seen in rats with complete lesions, but not in any of the animals with intrastriatal 6-OHDA (which showed > 5% DA fiber sparing in the medial striatum). Intrastriatally 6-OHDA-lesioned rats had a larger therapeutic window for L-DOPA than did rats with complete bundle lesions, since they exhibited an overall lower predisposition to dyskinesia but a similar degree of drug-induced motor improvement in a test of forelimb stepping. Our results are the first to demonstrate that selective and partial DA denervation in the sensorimotor part of the striatum can confer cellular and behavioral supersensitivity to L-DOPA, and that the phenomenology of L-DOPA-induced rat AIMs can be accounted for by the topography of DA denervation within the caudate-putamen.

Afferent Pathways↗
PubMed1988

Effect of the dopamine receptor agonist apomorphine on sensory input.

The study examines the hypothesis that changes in behavioural responsiveness induced by apomorphine reflect an effect of the drug on visual, tactile, vestibular, or proprioceptive sensory input. Rats were injected with apomorphine (1.25 mg/kg) and administered a neurological examination in which stimuli from the different sensory modalities were tested for their ability to elicit a limb placing response. Results indicate that these sensory stimuli were equally effective in eliciting reflex placing reactions in saline- and apomorphine-treated rats. Thus, contrary to the hypothesis, apomorphine does not appear to affect the reception of visual, tactile, vestibular, or proprioceptive sensory input. Tests of equilibration (righting) induced by static tilt revealed a fractionated response under apomorphine (0.6-5 mg/kg). Since the response to tilt probably involves striatal integration of vestibular and proprioceptive input, it is suggested that apomorphine disrupts sensory or sensorimotor integration.

Animals↗
PubMed1990

Lesions of the dopaminergic nigrostriatal system in neonatal rats: effects on the electrophysiological activity of striatal neurons recorded during adulthood.

The spontaneous activity of single striatal neurons was recorded extracellularly from 3-4-month-old adult rats that had been given dopamine (DA)-depleting brain lesions 3 days after birth. Behavioral observations made prior to recording indicated no gross sensorimotor deficits, yet subsequent biochemical analyses revealed that animals had sustained near-total DA depletions (greater than 99%). Electrophysiological results showed that the firing rates of type II striatal cells were greatly increased relative to control levels. This finding contrasts sharply with the effects of DA-depleting brain lesions given to adult animals, in which similarly high levels of striatal cell activity are invariably associated with akinesia.

Aging↗
PubMed2002

Hemispheric asymmetry and aging: right hemisphere decline or asymmetry reduction.

We review evidence for two models of hemispheric asymmetry and aging: the right hemi-aging model, which proposes that the right hemisphere shows greater age-related decline than the left hemisphere, and the hemispheric asymmetry reduction in old adults (HAROLD) model, which proposes that frontal activity during cognitive performance tends to be less lateralized in older than in younger adults. The right hemi-aging model is supported by behavioral studies in the domains of cognitive, affective, and sensorimotor processing, but the evidence has been mixed. In contrast, available evidence is generally consistent with the HAROLD model, which is supported primarily by functional neuroimaging evidence in the domains of episodic memory encoding and retrieval, semantic memory retrieval, working memory, perception, and inhibitory control. Age-related asymmetry reductions may reflect functional compensation or dedifferentiation, and the evidence, although scarce, tends to support the compensation hypothesis. The right hemi-aging and the HAROLD models are not incompatible. For example, the latter may apply to prefrontal regions and the former to other brain regions.

Aging↗
PubMed1993

Rapid reliable measurement of lesion parameters for studies of motor recovery after sensorimotor cortex injury in the rat.

Measurement of the ability of rats to traverse a narrow elevated beam has been used to quantitate motor recovery after unilateral injury to the sensorimotor cortex. Lesion extent is an important variable to consider in studies of the effects of drugs on beam-walking recovery. However, traditional histologic evaluation precludes neurochemical measurements in brain tissue. The present study was carried out to determine how well the dimensions of the lesion measured at the surface of the brain correlate with subsequent motor recovery in comparison with standard histology. The maximum medial extent of the lesion (closest approximation of the lesion to the inter-hemispheric fissure) was correlated with subsequent recovery (Spearman r = 0.61, P = 0.02) whereas the lesion surface area was not correlated with recovery (Spearman r = 0.25, P = 0.30). This data compared favorably with measures that were dependent on histologic tissue preparation. Furthermore, measurements of surface lesion parameters were highly reliable (intra- and inter-observer reliability for lesion surface maximum medial extent and lesion surface area were r2 = 0.88, 0.96, 0.97, and 0.96, P = 0.0001, respectively). Lesion surface parameters provide a valid and reliable measure of lesion size and extent for studies of beam-walking recovery after injury to the sensorimotor cortex.

Animals↗
PubMedDate not supplied

Inhibitory control of attention declines more than working memory during normal aging.

Changes in frontostriatal systems are believed to reduce the efficiency of executive cognitive functions during normal aging, especially the inhibitory control of attentional and behavioral responses. To characterize changes during normal aging in sensorimotor, working memory and inhibitory attentional systems, we tested 20 healthy elderly subjects (age 65-80) and 28 young adults (age 18-34) using oculomotor paradigms. Visually guided saccades of elderly subjects showed decreased peak velocity and increased reaction time, but not reduced accuracy, indicating selective age-related declines in sensorimotor systems. In an oculomotor working memory task, memory for spatial location information in elderly subjects was as accurate as in young adults. In contrast, elderly subjects demonstrated a significantly reduced ability to voluntarily inhibit eye movements toward flashed targets on an antisaccade task. These findings indicate changes in frontostriatal systems during normal aging that adversely affect volitional inhibitory processes but spare encoding and retrieval components of spatial working memory.

Adolescent↗
PubMed1999

Nocturnal motor coordination deficits in neuronal nitric oxide synthase knock-out mice.

Nitric oxide is formed in the brain primarily by neurons containing neuronal nitric oxide synthase (nNOS), though some neurons may express endothelial NOS (eNOS), and inducible NOS (iNOS) only occurs in neurons following toxic stimuli. Mice with targeted disruption of nNOS (nNOS-) display distended stomachs with hypertrophied pyloric sphincters reflecting loss of nNOS in myenteric plexus neurons. nNOS- animals resist brain damage following middle cerebral artery occlusions consistent with evidence that excess release of nitric oxide mediates neurotoxicity in ischemic stroke. Neuronal NOS- mice have no grossly evident defects in locomotor activity, breeding long-term depression in the cerebellum, long-term potentiation in the hippocampus, and overall sensorimotor function. However, nNOS- animals display excessive, inappropriate sexual behavior and dramatic increases in aggression. Because the cerebellum possesses the greatest levels of nNOS neurons in the brain, it was surprising that presumed cerebellar functions such as balance and coordination were grossly normal in nNOS- mice. These previous studies were all conducted during the day (between 1400 and 1600, lights on at 0700). We now report striking, discrete abnormalities in balance and motor coordination in nNOS-mice reflected selectively at night.

Animals↗
PubMed2003

Distinct forms of cholinergic modulation in parallel thalamic sensory pathways.

Mammalian thalamus is a critical site where early perception of sensorimotor signals is dynamically regulated by acetylcholine in a behavioral state-dependent manner. In this study, we examined how synaptic transmission is modulated by acetylcholine in auditory thalamus where sensory relay neurons form parallel lemniscal and nonlemniscal pathways. The former mediates tonotopic relay of acoustic signals, whereas the latter is involved in detecting and transmitting auditory cues of behavioral relevance. We report here that activation of cholinergic muscarinic receptors had opposite membrane effects on these parallel synaptic pathways. In lemniscal neurons, muscarine induced a sustained membrane depolarization and tonic firing by closing a linear K(+) conductance. In contrast, in nonlemniscal neurons, muscarine evoked a membrane hyperpolarization by opening a voltage-independent K(+) conductance. Depending on the level of membrane hyperpolarization and the strength of local synaptic input, nonlemniscal neurons were either suppressed or selectively engaged in detecting and transmitting synchronized synaptic input by firing a high-frequency spike burst. Immunohistochemical and Western blotting experiments showed that nonlemniscal neurons predominantly expressed M2 muscarinic receptors, whereas lemniscal cells had a significantly higher level of M1 receptors. Our data indicate that cholinergic modulation in the thalamus is pathway-specific. Enhanced cholinergic tone during behavioral arousal or attention may render synaptic transmission in nonlemniscal thalamus highly sensitive to the context of local synaptic activities.

Acetylcholine↗
PubMedDate not supplied

Brain gene expression during REM sleep depends on prior waking experience.

In most mammalian species studied, two distinct and successive phases of sleep, slow wave (SW), and rapid eye movement (REM), can be recognized on the basis of their EEG profiles and associated behaviors. Both phases have been implicated in the offline sensorimotor processing of daytime events, but the molecular mechanisms remain elusive. We studied brain expression of the plasticity-associated immediate-early gene (IEG) zif-268 during SW and REM sleep in rats exposed to rich sensorimotor experience in the preceding waking period. Whereas nonexposed controls show generalized zif-268 down-regulation during SW and REM sleep, zif-268 is upregulated during REM sleep in the cerebral cortex and the hippocampus of exposed animals. We suggest that this phenomenon represents a window of increased neuronal plasticity during REM sleep that follows enriched waking experience.

Analysis of Variance↗
PubMed1970

Facilitation of spindle-burst sleep by conditioning of electroencephalographic activity while awake.

A slow-wave electroencephalographic rhythm recorded from the sensorimotor cortex of the waking cat has been correlated behaviorally with the suppression of movement. Facilitation of this rhythm through conditioning selectively enhances a similar pattern recorded during sleep, the familiar spindle burst. The training also produced longer epochs of undisturbed sleep. The specific neural mechanism manipulated during wakefulness appears to function also in sleep and to be involved with the regulation of phasic motor behavior.

Animals↗
PubMed2003

Human theta oscillations related to sensorimotor integration and spatial learning.

oscillations in the rat hippocampus have been implicated in sensorimotor integration (Bland, 1986), especially during exploratory and wayfinding behavior. We propose that human cortical activity coordinates sensory information with a motor plan to guide wayfinding behavior to known goal locations. To test this hypothesis, we analyzed invasive recordings from epileptic patients while they performed a spatially immersive, virtual taxi driver task. Consistent with this hypothesis, we found oscillations during both exploratory search and goal-seeking behavior and, in particular, during virtual movement, when sensory information and motor planning were both in flux, compared with periods of self-initiated stillness. oscillations had different topographic and spectral characteristics during searching than during goal-seeking, suggesting that different cortical networks exhibit depending on which cognitive functions are driving behavior (spatial learning during exploration vs orienting to a learned representation during goal-seeking). In contrast, oscillations in the beta band appeared to be related to simple motor planning, likely a variant of the Rolandic mu rhythm. These findings suggest that human cortical oscillations act to coordinate sensory and motor brain activity in various brain regions to facilitate exploratory learning and navigational planning.

Adolescent↗
PubMedDate not supplied

[Status of the synapses of the end brain of rats exposed to the factors of space flight].

Using electron microscopy, synapses of different structures of the rat end brain related to cognitive and motor acts (sensorimotor cortex, caudate nucleus) as well as memory and behavior (hippocampus) were examined. Rats were exposed to ionizing radiation, super-high frequency, hypoxia, hyperoxia, vibration and acceleration (applied separately or in combination) which have been traditionally in the focus of space and aviation medicine. Brain interneuronal junctions were found to be very sensitive to the above effects, particularly ionizing radiation and hypoxia. Conversely, synapses were shown to be highly resistant to short-term hyperoxia and electromagnetic radiation. When combined effects were used, responses of interneuronal junctions depended on the irradiation dose and order of application of radiation and other flight factors.

Acceleration↗
PubMed2003

The effects of sex steroids and vasotocin on behavioral responses to visual and olfactory sexual stimuli in ovariectomized female roughskin newts.

Previous studies have found that vasotocin (AVT) administration to male roughskin newts (Taricha granulosa) enhances courtship clasping as well as appetitive responses to specific sexual stimuli and that treating female newts with androgens plus AVT induces the expression of male-typical courtship clasping (the selective clasping of females). However, the unique and/or interactive effects of sex steroids and AVT on appetitive responses to specific sexual stimuli have not yet been determined. To first identify male-typical, sexually dimorphic appetitive responses to female sexual stimuli, we tested intact newts during the breeding season and found that males, but not females, are attracted to female visual and pheromonal sexual stimuli. We then used ovariectomized (ovx) females implanted with empty silastic capsules (Blk) or with capsules containing testosterone (T), dihydrotestosterone (DHT), or estradiol (E2) and then injected with either saline or AVT to determine the effects of steroids and AVT, alone or in combination with each other, on male-typical behavioral responses to those stimuli. E2 treatment depressed responses toward female visual stimuli independently of AVT. On the other hand, only T-implanted, AVT-injected females displayed male-typical behavioral responses toward female olfactory stimuli, preferring to spend more time in proximity to female-scented than unscented newt models and selectively clasping the female-scented models. Together, these results support the conclusion that sex steroids and AVT influence behavioral responses to sexual stimuli via sensory-specific mechanisms. Furthermore, they suggest that T and AVT interact within the brain to influence sensorimotor processing in the pathways that integrate olfactory sexual stimuli into male-typical courtship behaviors.

Animals↗
PubMed2004

Reaching long-term goals based on local interaction between an organism and the environment: computer simulations based on adaptive behavior.

An agent-based computer simulation created using the adaptive-behavior approach has shown that in some cases it is possible to reach a long-term goal (defined here as a desirable place far removed from the agent in time and in space) without necessarily having an exhaustive, predefined plan of action, but rather by using a set of rules on sensorimotor couplings that govern the organism's local interaction with its environment. We used an agent-based simulation program that emulated a two-dimensional microworld in which agents interacted with their environment and other agents through a set of sensorimotor couplings to reach a long-term goal. The main hypothesis was that the sensorimotor coupling, which consisted of following other agents, led to the emergence of collective behavior that enabled the agents to attain the long-term goal. We systematically varied the sensorimotor couplings that allowed agents to follow other agents, agents' perceptual field length, and the number of obstacles. In total, there were 160 independent simulations for each design cell. Analysis supported the hypothesis and suggested that, in addition to the process of reaching long-term goals, other cognitive processes, such as categorization, memory, and reasoning, can be reconsidered bearing in mind the emergence of behavior and an approach based on interaction between the organism and its environment.

Adaptation, Physiological↗