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PubMed1997

Somatosensory contributions to c-fos activation within the caudal periaqueductal gray of lactating rats: effects of perioral, rooting, and suckling stimuli from pups.

In lactating rats, the immediate-early gene c-fos was previously shown to be highly activated in several brain sites by physical interaction with either suckling or nonsuckling pups but not by distal stimuli from pups, a non-pup stimulus, or no stimulation. Further, even greater levels of Fos-immunoreactivity (ir) occurred following suckling versus nonsuckling contact with pups in only 1 of over 25 sites--the caudal periaqueductal gray (cPAG) at an intercollicular level, lesions of which severely reduced the typical suckling-induced kyphotic nursing posture. Herein we further evaluated the effects and site-specificity of various somatosensory cues received from pups during 60 min on Fos-ir in the PAG of day 7 postpartum rats after a 48-h dam-litter separation. Dams interacting with suckling versus nonsuckling pups showed relatively high numbers of Fos-ir cells in the intercollicular cPAG site identified earlier, but not in three other rostrocaudal planes of the PAG. Elimination of rooting on the dam's ventrum by use of fully anesthetized pups did not further diminish Fos-ir in maternally behaving, nonsuckled dams. Perioral anesthesia of dams prior to reunion with the litter prevented retrieval and licking of pups but not pup-initiated nursing behavior, the duration of which was positively correlated with Fos-ir levels within the intercollicular cPAG. Thus, various somatosensory stimuli from pups activate c-fos in a discrete region of the cPAG but only interactions that include suckling and its behavioral consequences elicit maximal expression, consistent with a role for this midbrain site in the sensorimotor control of kyphotic nursing in rats.

Animals↗
PubMed2005

Treating the aging brain: cortical reorganization and behavior.

Aging comprises many physiological modifications, including structural and metabolic changes, yet little is known about how aging affects the way in which neurons process and integrate sensory information from the environments. Here the framework of "modified use" as a determinant of cortical reorganization was applied for the investigation of age-related modifications of cortical maps and processing, and of associated changes of behavior. The age-related changes of walking behavior in rats were contrasted with the parallel changes of sensorimotor processing developing at the cortical level. Based on the regional specificity of these changes attempts are made to separate age-related changes arising as a consequence of degeneration from a result of adaptable processes following reduced use at high age. Finally, findings from long-term treatment with the Ca2+-blocker nimodipine, or from housing animals under enriched environmental conditions to ameliorate aging effects were described. Combined, these results show the general treatability of age-related changes. The data imply that age-related changes can be reversed by short periods of training and stimulation schedules even if they have developed. Clearly, the development of specific measures to delay aging processes and to rehabilitate aged brains depends on future progress in understanding mechanisms and effects of aging.

Adaptation, Physiological↗
PubMed1986

Short term status epilepticus in rats causes specific behavioral impairments related to substantia nigra necrosis.

Status epilepticus (SE) was induced for 40 min by flurothyl in well oxygenated rats. This insult resulted in selective destruction of up to 65% of the substantia nigra pars reticulata. We investigated the short and long term behavioral effects of this damage. No deficits were observed in sensorimotor reactivity, locomotor coordination, spontaneous or apomorphine-stimulated locomotor activity in the rats with induced epilepsy. However, these rats exhibited a long-lasting enhancement of amphetamine-stimulated locomotor activity. We propose that this selective impairment is caused by the necrosis of the pars reticulata. This damage might lead to deficient regulation either of mesostriatal dopamine neurons innervating nc. accumbens, or of neurons in the mesencephalic reticular formation mediating the locomotor response initiated in the nc. accumbens.

Animals↗
PubMed1982

An assessment of the state hypothesis of animal "hypnosis' through an analysis of neocortical and hippocampal EEG in spontaneously immobile and hypnotized rabbits.

Hippocampal and neocortical EEG was studied in spontaneously immobile rabbits and in immobilized rabbits, "animal hypnosis.' Neocortical low voltage fast activity (LVFA) and hippocampal rhythmical slow activity (RSA) occurred spontaneously and were elicited by sensory stimulation, eserine and brain stimulation in normally immobile and hypnotized animals. Atropine sulfate blocked the LVFA and RSA that occurred during spontaneous immobility and hypnosis but not the LVFA and RSA that occurred during movement. RSA was also recorded from both CAI and dentate gyrus generators of the hippocampus during both types of immobility. The results show that hypnotized rabbits have the same type II (atropine-sensitive) EEG that is found in spontaneously immobile rabbits. The presence of type II EEG during hypnosis and its sustained sensitivity to stimulation is compatible with the view that the EEG activity is not uncoupled from its normal behavioral correlates. Perhaps normal EEG during animal hypnosis allows normal sensorimotor functions. This may permit the possibility of escape from predators at opportune moments once the immobility has served its defensive function.

Animals↗
PubMed1991

Rat strain and stock comparisons using a functional observational battery: baseline values and effects of amitraz.

A functional observational battery (FOB) was utilized to assess the effects of 3-day exposure to the formamidine pesticide amitraz in outbred Sprague-Dawley-derived and inbred Fischer-344-derived (F344) rats (both from Charles River Laboratories) and in outbred Long-Evans rats obtained from two commercial suppliers (Charles River Breeding Laboratories and Blue Spruce Farms). Significant strain and stock differences were obtained in baseline values for one-third of the FOB measures. In most cases, F344 rats were different from the others. Characteristic signs of amitraz exposure consisting of increased excitability, hyper-reactivity, and physiological and autonomic changes were evident in all treated rats. These effects increased with repeated dosing, and many were still present 6 days after dosing. On individual measures, there were differences between the strains and stocks in terms of sensitivity and time course of amitraz effects. In general, Blue Spruce Long-Evans rats displayed more effects of amitraz and F344 rats recovered more quickly than others. Although Sprague-Dawley rats showed the least effect overall, they displayed the largest increases in the sensorimotor responses to stimuli. These data indicate that although some behavioral and physiological parameters showed strain and supplier differences, in both baseline values and the effects of amitraz, conclusions concerning its neurotoxic potential in a screening context would be similar.

Animals↗
PubMed2004

Antisense knockdown of drebrin A, a dendritic spine protein, causes stronger preference, impaired pre-pulse inhibition, and an increased sensitivity to psychostimulant.

Drebrin located in dendritic spines regulates their morphological changes and plays a role in the synaptic plasticity via spine function. Reduced drebrin has been found in the brain of patients with Alzheimer's disease or Down's syndrome. To examine whether the down-regulation of drebrin protein levels causes deficits in higher brain function, such as memory or cognition, we performed antisense-induced knockdown of drebrin A expression in rat brain using an hemagglutinating virus of Japan (HVJ)-liposome gene transfer technique. We investigated the effects of drebrin in vivo knockdown on spatial memory in a water-maze task, sensorimotor gating in a pre-pulse-inhibition test, adaptive behaviors in an open-field test, and sensitivity to psychostimulant in an amphetamine-induced locomotor response. Rats with drebrin A in vivo knockdown displayed a stronger preference for a previous event due to perseverative behavior, impaired pre-pulse inhibition (PPI), increased locomotor activity, anxiety-like behavior, and an increased sensitivity to psychostimulant, suggesting behaviors related to schizophrenia. These findings indicated that decreased drebrin produces deficits in cognitive function but not in spatial memory, probably via hypofunction of dendritic spines.

Adaptation, Psychological↗
PubMed2005

Chronic administration of selective serotonin reuptake inhibitor (SSRI) paroxetine modulates human motor cortex excitability in healthy subjects.

The aim of the study was to investigate the effect of chronic administration of paroxetine (selective serotonin reuptake inhibitor: SSRI) on motor cortex excitability in healthy subjects by means of transcranial magnetic stimulation (TMS), functional magnetic resonance imaging (fMRI) and behavioral motor tests. In a randomized, double-blind, crossover study, twenty-one right-handed subjects received 20 mg daily of either paroxetine or a placebo over a period of 30 days separated by a period of 3 months wash-out. The TMS study is presented here correlated with some results of the motor behavior study (finger tapping test) and the fMRI study (primary sensorimotor cortex (S1M1) volume of activation). TMS was used to test motor threshold (MT), motor evoked potential recruitment curve (RC), cortical silent period (CSP) and paired-pulse intracortical inhibition and facilitation (ICI, ICF). Chronic administration of paroxetine did not modulate ICI or CSP but induced a significant enhancement of mean ICF (ANOVA P=0.04), which significantly correlated with increase of speed in a finger tapping test (P=0.02). This suggests a modulation of cortical interneuronal excitatory pathways without changes in the excitability of cortical inhibitory GABAergic interneurons. A decrease of RC (ANOVA P=0.05) was also observed after 30 days intake of paroxetine in comparison with placebo and was associated with changes of fMRI activation intensity (left S1M1 hypoactivation, ), without changes of S1M1 activation volume. Finally, the different modulation of RC and ICF after chronic administration of paroxetine compared to single dose (opposite effects) emphasizes the different pharmacological action of the drug at cortical level depending on its acute or long-term administration.

Adult↗
PubMed2004

The induced Roelofs effect: two visual systems or the shift of a single reference frame?

Cognitive judgments about an object's location are distorted by the presence of a large frame offset left or right of an observer's midline. Sensorimotor responses, however, seem immune to this induced Roelofs illusion, with observers able to accurately point to the target's location. These findings have traditionally been used as evidence for a dissociation of the visual processing required for cognitive judgments and sensorimotor responses. However, a recent alternative hypothesis suggests that the behavioral dissociation is expected if the visual system uses a single frame of reference whose origin (the apparent midline) is biased toward the offset frame. The two theories make qualitatively distinct predictions in a paradigm in which observers are asked to indicate the direction symmetrically opposite the target's position. The collaborative findings of two laboratories clearly support the biased-midline hypothesis.

Adult↗
PubMed2002

Tau filament formation and associative memory deficit in aged mice expressing mutant (R406W) human tau.

The R406W tau mutation found in frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) causes a hereditary tauopathy clinically resembling Alzheimer's disease. Expression of modest levels of the longest human tau isoform with this mutation under the control of the alpha-calcium-calmodulin-dependent kinase-II promoter in transgenic (Tg) mice resulted in the development of congophilic hyperphosphorylated tau inclusions in forebrain neurons. These inclusions appeared as early as 18 months of age. As with human cases, tau inclusions were composed of both mutant and endogenous wild-type tau, and were associated with microtubule disruption and flame-shaped transformations of the affected neurons. Straight tau filaments were recovered from Sarkosyl-insoluble fractions from only the aged Tg brains. Behaviorally, aged Tg mice had associative memory impairment without obvious sensorimotor deficits. Therefore, these mice that exhibit a phenotype mimicking R406W FTDP-17 provide an animal model for investigating the adverse properties associated with this mutation, which might potentially recapitulate some etiological events in Alzheimer's disease.

Aging↗
PubMed2000

Auditory responses from the frontal cortex in the short-tailed fruit bat Carollia perspicillata.

Based on neuroanatomical findings it was hypothesized that an area in the bat frontal cortex is part of a sensorimotor feedback loop and probably important to goal-directed behaviors guided by auditory information. The present report describes the basic stimulus preferences and response properties of neurons from this area in the short-tailed fruit bat Carollia perspicillata. Responses to acoustic stimuli mimicking biosonar pulse-echo (i.e. FM-FM) combinations were found to be facilitated throughout but only rarely exhibited tuning to pulse-echo delay. As opposed to the often sharply delay-tuned FM-FM neurons in the species' auditory cortex, frontal cortical FM-FM neurons seem to be suited for indicating the presence of an insonified object irrespective of its distance and hence are likely to function as novelty detectors and to trigger changes in the bats' orientation behavior.

Acoustic Stimulation↗
PubMed2000

Song replay during sleep and computational rules for sensorimotor vocal learning.

Songbirds learn a correspondence between vocal-motor output and auditory feedback during development. For neurons in a motor cortex analog of adult zebra finches, we show that the timing and structure of activity elicited by the playback of song during sleep matches activity during daytime singing. The motor activity leads syllables, and the matching sensory response depends on a sequence of typically up to three of the preceding syllables. Thus, sensorimotor correspondence is reflected in temporally precise activity patterns of single neurons that use long sensory memories to predict syllable sequences. Additionally, "spontaneous" activity of these neurons during sleep matches their sensorimotor activity, a form of song "replay." These data suggest a model whereby sensorimotor correspondences are stored during singing but do not modify behavior, and off-line comparison (e.g., during sleep) of rehearsed motor output and predicted sensory feedback is used to adaptively shape motor output.

Acoustic Stimulation↗
PubMed2004

Brain responses to ambient temperature fluctuations in fish: reduction of blood volume and initiation of a whole-body stress response.

Spatial and temporal ambient temperature variations directly influence cellular biochemistry and thus the physiology of ectotherms. However, many aquatic ectothermic species maintain coordinated sensorimotor function during large acute body-temperature changes, which points to a compensatory mechanism within the neural system. Here we used high-resolution functional magnetic resonance imaging to study brain responses to a drop of 10 degrees C of ambient water temperature in common carp. We observed a strong drainage of blood out of the brain as of 90 s after the onset of the temperature drop, which would be expected to reduce entry of cold blood arriving from the gills so that the change in brain temperature would be slower. Although oxygen content in the brain thus decreased, we still found specific activation in the preoptic area (involved in temperature detection and stress responses), the pituitary pars distalis (stress response), and inactivation of the anterior part of the midbrain tegmentum and the pituitary pars intermedia. We propose that the blood drainage from the brain slows down the cooling of the brain during an acute temperature drop. This could help to maintain proper brain functioning including sensorimotor activity, initiation of the stress response, and the subsequent behavioral responses.

Animals↗
PubMed2003

Cortical electrical stimulation combined with rehabilitative training: enhanced functional recovery and dendritic plasticity following focal cortical ischemia in rats.

This study assessed the behavioral and dendritic structural effects of combining subdural motor cortical electrical stimulation with motor skills training following unilateral sensorimotor cortex lesions in adult male rats. Rats were pre-operatively trained on a skilled forelimb reaching task, the Montoya staircase test, and then received endothelin-1 induced ischemic lesions of the sensorimotor cortex. Ten to 14 days later, electrodes were implanted over the peri-lesion cortical surface. Rats subsequently began 10 days of rehabilitative training on the reaching task in 1 of 3 conditions: 1. 50 Hz stimulation during training, 2. 250 Hz stimulation during training or 3. no stimulation. No significant difference in performance was found between the 250 Hz and no stimulation groups. The 50 Hz stimulation group had significantly greater rates of improvement with the impaired forelimb in comparison to 250 Hz and no stimulation groups combined. Fifty Hz stimulated animals also had a significant increase in the surface density of dendritic processes immunoreactive for the cytoskeletal protein, microtubule-associated protein 2, in the peri-lesion cortex compared to the other groups. These results support the efficacy of combining rehabilitative training with cortical electrical stimulation to improve functional outcome and cortical neuronal structural plasticity following sensorimotor cortical damage.

Analysis of Variance↗
PubMed2004

Long-term potentiation in an avian basal ganglia nucleus essential for vocal learning.

Vocal learning in songbirds provides an excellent model for sensorimotor learning in vertebrates, with an accessible, well-defined behavior and discrete neural substrate. The rich behavioral plasticity exhibited by songbirds, however, contrasts starkly with the scarcity of candidate cellular mechanisms. Here, we report for the first time on an activity-dependent form of synaptic plasticity in area X, a component of the song system required for song learning and song maintenance. In slice preparations of zebra finch area X, pairing of high-frequency presynaptic stimulation with postsynaptic depolarization induces Hebbian long-term potentiation (LTP) of the glutamatergic inputs to spiny neurons. This form of LTP requires activation of NMDA receptors and D1-like dopamine receptors. In addition, LTP is observed in birds as young as 47 d after hatching and also in adult birds but not in younger birds, providing evidence of developmental regulation of the onset of synaptic plasticity. These properties make this form of LTP the best known candidate mechanism for reinforcement-based vocal learning in juveniles and song maintenance in adult birds.

Animals↗
PubMed2006

Cocaine increases dopamine release by mobilization of a synapsin-dependent reserve pool.

Cocaine primarily exerts its behavioral effects by enhancing dopaminergic neurotransmission, amplifying dopamine-encoded sensorimotor integration. The presumed mechanism for this effect is inhibition of the dopamine transporter, which blocks dopamine uptake and prolongs the duration of dopamine in the extracellular space. However, there is growing evidence that cocaine can also augment dopamine release. Here, we directly monitored the actions of cocaine on dopamine release by using electrochemical detection to measure extracellular dopamine in the striatum of anesthetized mice. Cocaine enhanced the levels of striatal dopamine produced by electrical stimulation of dopaminergic neurons. Even after pretreatment with alpha-methyl-p-tyrosine, which depletes the readily releasable pool of dopamine, cocaine was still capable of elevating dopamine levels. This suggests that cocaine enhances dopamine release by mobilizing a reserve pool of dopamine-containing synaptic vesicles. To test this hypothesis, we examined electrically evoked dopamine release in synapsin I/II/III triple knock-out mice, which have impaired synaptic vesicle reserve pools. Knock-out of synapsins greatly reduced the ability of cocaine to enhance dopamine release with long stimulus trains or after depletion of the newly synthesized pool. We therefore conclude that cocaine enhances dopamine release and does so by mobilizing a synapsin-dependent reserve pool of dopamine-containing synaptic vesicles. This capacity to enhance exocytotic release of dopamine may be important for the psychostimulant actions of cocaine.

Animals↗
PubMed1983

Oral sensorimotor therapy in the developmentally disabled: a multiple baseline study.

The efficacy of a program of sensorimotor facilitation procedures to improve oral motor function and feeding behaviors in students with severe developmental delay was explored. Four severely handicapped students were administered the oral habilitation program using a multiple baseline across-subjects design with staggered introduction of the treatment. Graphic analysis and the split middle method of trend estimation revealed that one subject evidenced an increase in weight and improved oral motor evaluation as a result of the intervention. Two other subjects displayed partial improvement. The correlates of treatment effectiveness are briefly discussed and the need for continued investigation is emphasized.

Adult↗
PubMed1997

Spatially selective auditory responses in the superior colliculus of the echolocating bat.

When a bat approaches a target, it continuously modifies its echolocation sounds and relies on incoming echo information to shape the characteristics of its subsequent sonar cries. In addition, acoustic information about the azimuth and elevation of a sonar target elicits orienting movements of the head and pinnae toward the sound source. This requires a common sensorimotor interface, where echo information is used to guide motor behaviors. Using single-unit neurophysiological methods and free-field auditory stimulation, we present data on biologically relevant specializations in the superior colliculus (SC) of the bat for orientation by sonar. In the bat's SC, two classes of spatially tuned neurons are distinguished by their sensitivity to echoes. One population shows facilitated, delay-tuned responses to pairs of sounds, simulating sonar emissions and echoes. Delay tuning, related to encoding target range, may play a role in guiding motor responses in echolocation, because the bat adjusts its emissions with changes in target distance. The delay-facilitated response depends on the direction of stimulation and on the temporal relationship between the simulated emission and echo in the sound pair, suggesting that this class of neurons represents the location of a target in three dimensions. A second population encodes the target in two dimensions, azimuth and elevation, and does not show a facilitated response to echoes delivered from any locus. Encoding of azimuth and elevation may be important for directing head aim, and this class may function in transforming auditory spatial information into signals used to guide acoustic orientation.

Acoustic Stimulation↗
PubMed1990

Ketamine effects on somatosensory cortical single neurons and on behavior in rats.

The neurophysiological effects of ketamine were studied at the single-neuron level in the somatosensory cortex of unanesthetized rats behaving in a treadmill movement paradigm. Chronically implanted 25-microns microwire electrodes were used to record spontaneous discharge, sensory responses, and sensorimotor-correlated activity of single neurons before and after ketamine administration. Extracellular action potentials of up to six single neurons were simultaneously recorded for several days, allowing ketamine effects to be tested repeatedly on the same neurons. Videotaped recordings obtained during each experiment were used to measure both the sensorimotor properties of the neurons and the changes in these measures caused by different doses of ketamine. Behaviorally, ketamine produced restless-hyperactive behavior at subanesthetic doses from 5 to 20 mg/kg (intramuscularly). At higher doses (30-50 mg/kg) the rats became cataleptic and immobile after the initial hyperactive period. Whereas the spontaneous rates of most neurons were reduced or unchanged after subanesthetic doses, a subgroup (27% of the total) exhibited markedly increased firing rates. This excitation was of a tonic nature, persisting for a dose-dependent duration in a manner that was not correlated with any of the behavioral effects of the drug. In further analyses, ketamine suppressed the sensory responses of virtually all of the recorded neurons. In particular, low doses of ketamine suppressed "sensorimotor" firing (mainly proprioceptive responses) of neurons in relation to active limb movement. It also suppressed virtually all neuronal sensory responses to the sudden onset of treadmill movement, although the time-course of this effect varied from neuron to neuron. These results reveal two separable effects of ketamine: (a) a strong inhibition of all somatosensory responsiveness in this area and (b) a tonic excitatory influence expressed heterogeneously on a subgroup of neurons. This coexistence of cortical neuronal excitation and sensory suppression in the same cortical region may explain in part the mechanism of dissociative anesthesia and hallucinatory side effects observed in humans during emergence from ketamine anesthesia.

Action Potentials↗