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PubMed2007

Active spatial perception in the vibrissa scanning sensorimotor system.

Haptic perception is an active process that provides an awareness of objects that are encountered as an organism scans its environment. In contrast to the sensation of touch produced by contact with an object, the perception of object location arises from the interpretation of tactile signals in the context of the changing configuration of the body. A discrete sensory representation and a low number of degrees of freedom in the motor plant make the ethologically prominent rat vibrissa system an ideal model for the study of the neuronal computations that underlie this perception. We found that rats with only a single vibrissa can combine touch and movement to distinguish the location of objects that vary in angle along the sweep of vibrissa motion. The patterns of this motion and of the corresponding behavioral responses show that rats can scan potential locations and decide which location contains a stimulus within 150 ms. This interval is consistent with just one to two whisk cycles and provides constraints on the underlying perceptual computation. Our data argue against strategies that do not require the integration of sensory and motor modalities. The ability to judge angular position with a single vibrissa thus connects previously described, motion-sensitive neurophysiological signals to perception in the behaving animal.

Animals↗

PubMedDate not supplied

Coherence analysis of electrical activity in the rabbit brain during the process of substitution of dominants.

Coherence analysis was used to study intercenter relationships between biopotentials in the sensorimotor cortex (forelimb and blink representation areas) and the visual cortex in both hemispheres and the ventrolateral nucleus of the thalamus (VPL) of the left and right thalami during the formation of a motor defensive dominant (electrical stimulation of the limb skin) on a background of an induced (by stimulation of the cornea with an air jet) blink dominant. Characteristic electrophysiological measures of the dominant state (increases in the mean coherence level of potentials in the delta frequency range in structures involved in the functional defensive limb reflex system), along with the absence of behavioral manifestations of the motor dominant in the blink dominant, indicated that a cryptic potential dominant focus was created in the CNS in these conditions, and that this affected ongoing animal activity.

Aggression↗

PubMedDate not supplied

LY354740: a metabotropic glutamate receptor agonist which ameliorates symptoms of nicotine withdrawal in rats.

LY354740 is a conformationally constrained analog of glutamate with high selectivity and nanomolar agonist activity at Group II metabotropic glutamate receptors (mGluRs). This orally active compound is a new drug candidate which is being developed for the treatment of anxiety. In this study, LY354740 was investigated in a model of nicotine withdrawal using the acoustic startle reflex (sensorimotor reactivity) in rats. Nicotine (6 mg/kg/day) was administered for 12 days subcutaneously by osmotic minipumps. After 12 days the pumps were removed and the animals were allowed to go through spontaneous withdrawal. Cessation of chronic nicotine exposure led to increased startle responding for 4 days following withdrawal. Treatment with LY354740 (0.0001-0.1 mg/kg, i.p.; 0.03-3 mg/kg, oral) produced a dose-dependent attenuation of the enhanced auditory startle responding following withdrawal of nicotine with intraperitoneal and oral ED50 values of 0.003 mg/kg and 0.7 mg/kg, respectively. These effects were stereoselective since the (-)-enantiomer of LY354740, LY366563, was without effect in this model. LY354740 produced no changes in the sensorimotor reactivity of rats not exposed to nicotine at oral doses up to 10 mg/kg. These data support the functional role of mGluR agonists in nicotine withdrawal and indicate that LY354740 may be efficacious in reducing the symptoms associated with nicotine withdrawal during smoking cessation in humans.

Animals↗

PubMed1994

Temporal and kinematic properties of motor behavior reflected in mentally simulated action.

Related perceptual, motor, and cognitive performances were examined to reveal the accuracy of the properties of action spontaneously represented when mentally simulating moving one's hand. The kinematic configuration of the body represented and transformed in mental simulations was not fixed or canonical but corresponded to one's current configuration. Mental simulation time mimicked movement time for natural efficient movement from a posture midway between each of the hand's joint limits into many other postures. Equal time was required for simulated and real movements into more common, comfortable postures; shorter but proportional time was required for simulated movement than real movement into less common postures that involved longer trajectories, coordinated activity at more joints, motion near extremes of joint limits, and uncomfortable kinesthetic sensations. The findings suggest that sensorimotor structures support mental simulations of actions.

Functional Laterality↗

PubMed2005

Neurexophilin 3 is highly localized in cortical and cerebellar regions and is functionally important for sensorimotor gating and motor coordination.

Neurexophilin 3 (Nxph3) is a specific ligand of synaptic alpha-neurexins that are essential for efficient neurotransmitter release. Previous biochemical work demonstrated that Nxph3 interacts with an extracellular domain of alpha-neurexins in a tight complex; however, no information is available on the localization or functional role of Nxph3 in the brain. Here, we generated lacZ reporter gene knock-in mice to investigate the distribution of Nxph3 at the single-cell level and Nxph3 knockout mice to examine its functional importance. Nxph3 expression was restricted mostly to subplate-derived neurons in cortical layer 6b, granule cells in the vestibulocerebellum, and Cajal-Retzius cells during development. Colabeling experiments demonstrated that neurons expressing Nxph3 do not belong to a uniform cell type. Morphological analyses and systematic behavioral testing of knockout mice revealed no anatomical defects but uncovered remarkable functional abnormalities in sensory information processing and motor coordination, evident by increased startle response, reduced prepulse inhibition, and poor rotarod performance. Since Nxph3-deficient mice behaved normally while performing a number of other tasks, our data suggest an important role for Nxph3 as a locally and temporally regulated neuropeptide-like molecule, presumably acting in a complex with alpha-neurexins in select neuronal circuits.

Alleles↗

PubMed2001

Neuropsychological analyses of impulsiveness in childhood hyperactivity.

BACKGROUND: Neuropsychological analyses of impulsiveness are needed to refine assessment of attention-deficit hyperactivity disorder (ADHD). AIMS: To investigate specific impairments in hyperactive children in a neuropsychological task battery of impulsiveness, the Maudsley Attention and Response Suppression (MARS) task battery, and to identify the neural substrates. METHOD: Impulsiveness was assessed using different tasks of inhibitory control and time management (MARS) in 55 children with ADHD, other diagnoses and controls. Functional magnetic resonance images were obtained from adolescents with and without ADHD during three of the tasks. RESULTS: Children with ADHD, but not psychiatric controls, were impaired on tests of response inhibition, but not of motor timing. Reduced right prefrontal activation was observed in hyperactive adolescents during higher level inhibition and delay management, but not during simple sensorimotor coordination. CONCLUSIONS: Attention-deficit hyperactivity disorder is characterised by specific deficits in tasks of motor response inhibition, but not motor timing, and by dysfunction of frontostriatal brain regions.

Adolescent↗

PubMed2001

Prolonged exposure to low doses of ozone: short- and long-term changes in behavioral performance in mice.

Two separate experiments were designed to assess the effects of ozone exposure on outbred CD-1 mice. In the first experiment, adult males were exposed continuously to O3 at 0, 0.3, or 0.6 ppm for 30 days and their behavior was assessed in a 5-min open-field test on exposure days 4 and 19 and on day 3 after the end of the exposure phase. In addition, mice performed a Morris water maze task from exposure day 24 to 28. In the second experiment, adult females were exposed from 30 days prior to the formation of breeding pairs until gestational day 17 to the same doses used in the first experiment. Litters were fostered at birth to untreated dams and neurobehavioral development of the offspring was investigated until adulthood. Specifically, somatic and sensorimotor development [postnatal day (PND) 2-20], homing performance (PND 12), motor activity (PND 21), passive avoidance (PND 22-23), water maze performances (PND 70-74), and response to a nociceptive stimulus (PND 100) were assessed. Results from both experiments confirm that exposure to O3 slightly but selectively affected neurobehavioral performance in rodents. Exposure to O3 did not grossly affect neurobehavioral development, whereas it consistently impaired reversal learning in the Morris water maze test in both prenatally and adult exposed mice. Moreover, longer latency to step-through in the first trial of the passive avoidance test and a decrease in wall rearing in the hot-plate test were recorded in O3 prenatally exposed mice. Except for the first open-field test, altered responses were observed only in animals exposed at the intermediate concentration of the gas. Adaptation and/or onset of compensatory mechanisms might be responsible for the lack of linear dose-response relationships.

Adaptation, Physiological↗

PubMed1986

A critical period for macromolecular synthesis in long-term heterosynaptic facilitation in Aplysia.

Both long-term and short-term sensitization of the gill and siphon withdrawal reflex in Aplysia involve facilitation of the monosynaptic connections between the sensory and motor neurons. To analyze the relationship between these two forms of synaptic facilitation at the cellular and molecular level, this monosynaptic sensorimotor component of the gill-withdrawal reflex of Aplysia can be reconstituted in dissociated cell culture. Whereas one brief application of 1 microM serotonin produced short-term facilitation in the sensorimotor connection that lasted minutes, five applications over 1.5 hours resulted in long-term facilitation that lasted more than 24 hours. Inhibitors of protein synthesis or RNA synthesis selectively blocked long-term facilitation, but not short-term facilitation, indicating that long-term facilitation requires the expression of gene products not essential for short-term facilitation. Moreover, the inhibitors only blocked long-term facilitation when given during the serotonin applications; the inhibitors did not block the facilitation when given either before or after serotonin application. These results parallel those for behavioral performance in vertebrates and indicate that the critical time window characteristic of the requirement for macromolecular synthesis in long-term heterosynaptic facilitation is not a property of complex circuitry, but an intrinsic characteristic of specific nerve cells and synaptic connections involved in the long-term storage of information.

Amanitins↗

PubMed2002

A real-time state predictor in motor control: study of saccadic eye movements during unseen reaching movements.

Theoretical motor control predicts that because of delays in sensorimotor pathways, a neural system should exist in the brain that uses efferent copy of commands to the arm, sensory feedback, and an internal model of the dynamics of the arm to predict the future state of the hand (i.e., a forward model). We tested this theory under the hypothesis that saccadic eye movements, tracking an unseen reaching movement, would reflect the output of this state predictor. We found that in unperturbed reaching movements, saccade occurrence at any time t consistently provided an unbiased estimate of hand position at t + 196 msec. To investigate the behavior of this predictor during feedback error control, we applied 50 msec random-force perturbations to the moving hand. Saccades showed a sharp inhibition at 100 msec after perturbation. At approximately 170 msec, there was a sharp increase in saccade probabilities. These postperturbation saccades were an unbiased estimator of hand position at saccade time t + 150 msec. The ability of the brain to guide saccades to the future position of the hand failed when a force field unexpectedly changed the dynamics of the hand immediately after perturbation. The behavior of the eyes suggested that during reaching movements, the brain computes an estimate of future hand position based on an internal model that relies on real-time proprioceptive feedback. When an error occurs in reaching movements, the estimate of future hand position is recomputed. The saccade inhibition period that follows the hand perturbation may indicate the length of time it takes for this computation to take place.

Arm↗

PubMed1986

Contextual control of trigeminal sensorimotor function.

Simple actions, such as rhythmic tongue protrusions, forelimb facial strokes, and forelimb flails, are emitted by rats both during taste-elicited ingestion/aversion and during postprandial grooming. This study combined peripheral trigeminal deafferentation with a computer-assisted video analysis of action form to examine the use of cutaneous feedback from the face in action production. Changes in action form after deafferentation were found to be context-dependent: Deformations characterized rhythmic tongue protrusions when emitted in ingestive but not in grooming contexts. The opposite was true for alterations in forelimb action. Further, postprandial grooming as a whole was found to comprise distinct sequentially defined phases. Actions occurring in one highly stereotyped sequence phase were protected from deafferentation effects, although the same actions occurring outside of this phase were not. The results suggest that behavioral context (e.g., grooming versus ingestive set, sequence phase) can shift the integration of sensory guided and endogenous mechanisms that pattern simple actions.

Animals↗

PubMed1981

Peripherally administered serotonin decreases food intake in rats.

We report that intraperitoneal injection of serotonin produces a dose-related decrease in the food intake of hungry rats. The efficacy of serotonin was increased by prior treatment with clorgyline, a type A monoamine oxidase inhibitor. Doses of serotonin which were anorectic did not significantly impair locomotor activity or sensorimotor performance. Further, 2 mg/kg serotonin (ED50 on food intake) did not produce a conditioned taste aversion when paired repeatedly with sucrose ingestion. We conclude that the anorectic effects of serotonin are not secondary to nonspecific effects of the agent, and suggest that peripheral serotonin may play a role in normal satiation.

Animals↗

PubMed2000

The involvement of ventral tegmental area cholinergic muscarinic receptors in classically conditioned fear expression as measured with fear-potentiated startle.

Accumulating evidence suggests that dopamine (DA) neurons in the ventral tegmental area (VTA) contribute to the complex amygdala-based neurocircuitry that mediates fear-motivated behaviors. Because of acetylcholine's (ACh) role in DA neuronal activation, the involvement of VTA cholinergic muscarinic receptors in Pavlovian conditioned fear responding was evaluated in the present study. Fear-potentiated startle was used to assess the effects of intraVTA infused methylscopolamine on conditioned fear performance in laboratory rats. Application of this nonspecific muscarinic receptor antagonist to VTA neurons was observed to inhibit the ability of a conditioned stimulus (CS) previously paired with footshock to enhance the amplitude of the acoustic startle reflex. Doses of methylscopolamine that blocked conditioned fear expression did not alter baseline sensorimotor responding. These results identify ACh neurotransmission in the VTA as a potential excitatory mechanism underlying the fear-arousing properties of threatening environmental stimuli.

Acetylcholine↗

PubMedDate not supplied

A 6 D.O.F. opto-inertial tracker for virtual reality experiments in microgravity.

Gravity plays a role in many different levels of human motor behavior. It dictates the laws of motion of our body and limbs, as well as of the objects in the external world with which we wish to interact. The dynamic interaction of our body with the world is molded within gravity's constraints. The role played by gravity in the perception of visual stimuli and the elaboration of human movement is an active research theme in the field of Neurophysiology. Conditions of microgravity, coupled with techniques from the world of virtual reality, provide a unique opportunity to address these questions concerning the function of the human sensorimotor system. The ability to measure movements of the head and to update in real time the visual scene presented to the subject based on these measurements is a key element in producing a realistic virtual environment. A variety of head-tracking hardware exists on the market today, but none seem particularly well suited to the constraints of working with a space station environment. Nor can any of the existing commercial systems meet the more stringent requirements for physiological experimentation (high accuracy, high resolution, low jitter, low lag) in a wireless configuration. To this end, we have developed and tested a hybrid opto-inertial 6 degree-of-freedom tracker based on existing inertial technology. To confirm that the inertial components and algorithms will function properly, this system was tested in the microgravity conditions of parabolic flight. Here we present the design goals of this tracker, the system configuration and the results of 0g and 1g testing.

Acceleration↗

PubMed1978

Evaluation of a patterning treatment for retarded children.

Three groups, each with 15 seriously retarded institutionalized children, were employed to evaluate a modification of the sensorimotor patterning treatment developed at the Institutes for the Achievement of Human Potential (IAHP). The treatment group received a program modeled after the IAHP methods for approximately two hours per day, five days per week, for one year. For the same length of time, a matched motivational control group participated in activities with foster grandparents designed to create positive, success-oriented interactions to improve self-esteem and feelings of efficacy. A no treatment group continued to receive the standard care of the institution, which was enlightened and resident-oriented. A wide variety of behavioral measures were employed, including the IAHP Developmental Profile, IQ, motor and language development scales, and measures of affective, social, and maladaptive behaviors. On the majority of the measures there were no differences in posttest performance among any of the three groups. In no case did the pattern of change of the treatment group differ from that of its crucial comparison, the motivation group. However, all three groups showed some improvement in performance between the beginning and end of the study. It was concluded that the patterning treatment investigated in this study cannot be recommended for seriously retarded children.

Academies and Institutes↗

PubMed1999

Effects of sustained cocaine exposure on sensorimotor gating of startle in rats.

Deficient sensorimotor gating, as measured by a relative loss of prepulse inhibition (PPI) of the startle reflex, has been reported in schizophrenia patients and in rats treated acutely with dopamine (DA) agonists or other psychotomimetic agents. For this reason, PPI has been used as a cross-species measure for studying the neurochemistry of specific information processing deficits in schizophrenia. Cocaine is a DA reuptake inhibitor which can precipitate psychosis after sustained use in humans. In rats, sustained exposure to cocaine results in neuropathological and neurochemical changes in several brain regions, and is also associated with specific prolonged behavioral abnormalities. In the present study, we examined the effects of both acute and sustained cocaine administration on PPI and other measures of the startle reflex in rats. Cocaine produced a significant, dose-dependent reduction in PPI, both after acute administration, and after 3 days of sustained administration via implanted subcutaneous pellets. PPI returned to control levels when rats were tested 10 days after sustained (5 day) cocaine administration. The effects of acute cocaine administration on PPI are consistent with those of other DA agonists and psychotomimetics, but PPI does not appear to be sensitive to lasting effects of a method of prolonged cocaine administration associated with neuropathological and neurochemical changes in several brain regions.

Acoustic Stimulation↗

PubMed2002

Coordination dynamics of learning and transfer across different effector systems.

If different effector systems share a common task-specific coordination dynamics, transfer and generalization of sensorimotor learning are predicted. Subjects learned a visually specified phase relationship with either the arms or the legs. Coordination tendencies in both effector systems were evaluated before and after practice to detect attractive states of the coordination dynamics. Results indicated that learning a novel relative phase with a single effector system spontaneously transferred to the other, untrained effector system. Transfer was revealed not only as improvements in performance but also as modifications of each system's initial (prelearning) coordinative landscape. What is learned, appears to be a high-level but neurally instantiated dynamic representation of skilled behavior that proves to be largely effector independent, at least across anatomically symmetric limbs.

Adult↗

PubMed1994

Lesions of the pedunculopontine tegmental nucleus abolish catalepsy and locomotor depression induced by morphine.

The cataleptic and locomotor depressant effects of morphine are mediated by a series of neural structures, all of which project to the pedunculopontine tegmental nucleus (PPTg). To test the idea that the PPTg is also involved in mediating morphine's effect on these behaviours, we examined catalepsy and spontaneous motor activity following bilateral lesions of the PPTg (0.5 microliters of 0.1 M N-methyl-D-aspartate infused over 10 min). We also examined the effect of PPTg lesions on motor functioning by observing sensorimotor responses, limb use, muscle tone and locomotion. PPTg lesions completely abolished the catalepsy and decreased activity that normally follows morphine administration. In addition lesioned animals exhibited increased muscle tone, and impairments in limb use and righting reflexes. Although the deficits were subtle, these results confirm that damage to the PPTg is associated with motor abnormalities.

Acoustic Stimulation↗

PubMed1987

Assessing communicative intents in young children: low structured observation or elicitation tasks?

This longitudinal study examines the effectiveness of two different assessment methodologies, low structured observation and structured elicitation tasks, to obtain communicative intents from 35 sensorimotor children. The subjects, 9 months of age at the onset of the study, were observed under the two experimental conditions every 3 months, for a 15-month period. The results reveal differences between the two approaches that vary according to the age of the child and eliciting context. The implications of the findings are examined.

Child Behavior↗