The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform

John I. Simpson - One of the best experts on this subject based on the ideXlab platform.

  • Visuo-Vestibular Information Processing by Unipolar Brush Cells in the Rabbit Flocculus
    The Cerebellum, 2015
    Co-Authors: Robert A. Hensbroek, Boeke J. Beugen, Jun Maruta, Tom J H Ruigrok, John I. Simpson
    Abstract:

    The unipolar brush cell (UBC) is a glutamatergic granular layer interneuron that is predominantly located in the vestibulocerebellum and parts of the vermis. In rat and rabbit, we previously found using juxtacellular labeling combined with spontaneous activity recording that cells with highly regular spontaneous activity belong to the UBC category. Making use of this signature, we recorded from floccular UBCs in both anesthetized and awake rabbits while delivering visuo-vestibular stimulation by using sigmoidal rotation of the whole animal. In the anesthetized rabbit, the activity of the presumed UBC units displayed a wide variety of modulation profiles that could be related to aspects of head velocity or acceleration. These modulation profiles could also be found in the awake rabbit where, in addition, they could also carry an eye Position Signal. Furthermore, units in the awake rabbit could demonstrate rather long response latencies of up to 0.5 s. We suggest that the UBCs recorded in this study mostly belong to the type I UBC category (calretinin-positive) and that they can play diverse roles in floccular visuo-vestibular information processing, such as transformation of velocity-related Signals to acceleration-related Signals.

  • REVIEW Visuo-Vestibular Information Processing by Unipolar Brush Cells in the Rabbit Flocculus
    2015
    Co-Authors: John I. Simpson
    Abstract:

    # The Author(s) 2015. This article is published with open access at Springerlink.com Abstract The unipolar brush cell (UBC) is a glutamatergic granular layer interneuron that is predominantly located in the vestibulocerebellum and parts of the vermis. In rat and rabbit, we previously found using juxtacellular labeling combined with spontaneous activity recording that cells with highly reg-ular spontaneous activity belong to the UBC category.Making use of this signature, we recorded from floccular UBCs in both anesthetized and awake rabbits while delivering visuo-vestibular stimulation by using sigmoidal rotation of the whole animal. In the anesthetized rabbit, the activity of the presumed UBC units displayed a wide variety of modulation profiles that could be related to aspects of head velocity or acceleration. These modulation profiles could also be found in the awake rabbit where, in addition, they could also carry an eye Position Signal. Furthermore, units in the awake rabbit could demonstrate rather long response latencies of up to 0.5 s. We suggest that the UBCs recorded in this study mostly belong to the type I UBC category (calretinin-positive) and that they can play diverse roles in floccular visuo-vestibular information processing, such as transformation of velocity-related Signals to acceleration-related Signals

Michael E Goldberg - One of the best experts on this subject based on the ideXlab platform.

  • Monkey primary somatosensory cortex has a proprioceptive representation of eye Position.
    Progress in brain research, 2008
    Co-Authors: Mingsha Zhang, Xiaolan Wang, Michael E Goldberg
    Abstract:

    Abstract: The visual system is tied to the retina. Because the eyes move in the orbit, and the head moves on the body, accurate location of an object in extrapersonal space cannot simply result from a visual Signal. Instead, the retinal Signal must be combined with an estimate of where the eyes are in the orbit, and where the head is in space, to calculate where that object is relative to the observer. There is abundant evidence for eye Position Signals in various areas of the visual cortex. However, the source of that eye Position Signal is unknown. Estimates of eye Position can arise from two different sources. One is outflow, an ‘efference copy’ or ‘corollary discharge’ which might arise from some eye Position Signal used to specify eye Position for the eye muscles. The second source is inflow, a direct proprioceptive Signal from the muscles themselves. Nevertheless, neither a proprioceptive representation of eye Position nor corollary discharge of a motor command for eye Position has ever been demonstrated unambiguously in the cerebral cortex. We recently discovered the neuronal representation of proprioceptive eye Position Signal in monkey primary somatosensory cortex.

  • the proprioceptive representation of eye Position in monkey primary somatosensory cortex
    Nature Neuroscience, 2007
    Co-Authors: Xiaolan Wang, Mingsha Zhang, Ian S Cohen, Michael E Goldberg
    Abstract:

    The cerebral cortex must have access to an eye Position Signal, as humans can report passive changes in eye Position in total darkness, and visual responses in many cortical areas are modulated by eye Position. The source of this Signal is unknown. Here we demonstrate a representation of eye Position in monkey primary somatosensory cortex, in the representation of the trigeminal nerve, near cells with a tactile representation of the contralateral brow. The neurons have eye Position Signals that increase monotonically with increasing orbital eccentricity from near the center of gaze, with directionally selectivity tuned in a Gaussian manner. All directions of eye Position are represented in a single hemisphere. The Signal is proprioceptive, because it can be obliterated by anesthetizing the contralateral orbit. It is not related to foveal or peripheral visual stimulation, and it represents the Position of the eye in the head and not the angle of gaze in space.

Robert A. Hensbroek - One of the best experts on this subject based on the ideXlab platform.

  • Visuo-Vestibular Information Processing by Unipolar Brush Cells in the Rabbit Flocculus
    The Cerebellum, 2015
    Co-Authors: Robert A. Hensbroek, Boeke J. Beugen, Jun Maruta, Tom J H Ruigrok, John I. Simpson
    Abstract:

    The unipolar brush cell (UBC) is a glutamatergic granular layer interneuron that is predominantly located in the vestibulocerebellum and parts of the vermis. In rat and rabbit, we previously found using juxtacellular labeling combined with spontaneous activity recording that cells with highly regular spontaneous activity belong to the UBC category. Making use of this signature, we recorded from floccular UBCs in both anesthetized and awake rabbits while delivering visuo-vestibular stimulation by using sigmoidal rotation of the whole animal. In the anesthetized rabbit, the activity of the presumed UBC units displayed a wide variety of modulation profiles that could be related to aspects of head velocity or acceleration. These modulation profiles could also be found in the awake rabbit where, in addition, they could also carry an eye Position Signal. Furthermore, units in the awake rabbit could demonstrate rather long response latencies of up to 0.5 s. We suggest that the UBCs recorded in this study mostly belong to the type I UBC category (calretinin-positive) and that they can play diverse roles in floccular visuo-vestibular information processing, such as transformation of velocity-related Signals to acceleration-related Signals.

Yesheng Zhu - One of the best experts on this subject based on the ideXlab platform.

  • Half-soft starting control of switched reluctance motor using discrete Position Signal processing
    Cluster Computing, 2017
    Co-Authors: Guobao Zhang, Ling Wang, Yongming Huang, Yesheng Zhu
    Abstract:

    To solve the problem that the switched reluctance motor (SRM) may have harmful impact on the shaft during the starting process, a half-S soft starting control method is proposed. The switch Signal is given based on the discrete Position Signal of SRM without the requirement of accurate rotor Position information. In the process of the motor from static to rotation, the current step chopping soft starting is adopted to prevent the phase current from flowing; In starting acceleration stage, the edge Signal of discrete Position is used as the control period. By using sliding mode control, the increment of the rotation speed is identical at each Position Signal interval. The speed increased exponentially within the rated output power of motor. Through using Matlab/Simulink environment and switched reluctance motor drive platform, this method was validated, and the results reveals that the proposed method is able to achieve smooth starting and reduce the harmful impact on the mechanical system which shows high application value in the development field of SRM type electric vehicle.

Knut Drewing - One of the best experts on this subject based on the ideXlab platform.

  • Haptic shape perception from force and Position Signals varies with exploratory movement direction and the exploring finger.
    Attention perception & psychophysics, 2009
    Co-Authors: Knut Drewing, Lukas Kaim
    Abstract:

    We investigated how exploratory movement influences Signal integration in active touch. Participants judged the amplitude of a bump specified by redundant Signals: When a finger slides across a bump, the finger's Position follows the bump's geometry (Position Signal); simultaneously, it is exposed to patterns of forces depending on the gradient of the bump (force Signal). We varied amplitudes specified by force Signals independently of amplitudes specified by Position Signals. Amplitude judgment was a weighted linear function of the amplitudes specified by both Signals, under different exploratory conditions. The force Signal's contribution to the judgment was higher when the participants explored with the index finger, as opposed to the thumb, and when they explored along a tangential axis, as opposed to a radial one (pivot congruent with shoulder joint). Furthermore, for tangential, as compared with radial, axis exploration, amplitude judgments were larger (and more accurate), and amplitude discrimination was better. We attribute these exploration-induced differences to biases in estimating bump amplitude from force Signals. Given the choice, the participants preferred tangential explorations with the index finger-a behavior that resulted in good discrimination performance. A role for an active explorer, as well as biases that depend on exploration, should be taken into account when Signal integration models are extended to active touch.

  • Material properties determine how force and Position Signals combine in haptic shape perception.
    Acta psychologica, 2008
    Co-Authors: Knut Drewing, Thomas V. Wiecki, Marc O. Ernst
    Abstract:

    When integrating estimates from redundant sensory Signals, humans seem to weight these estimates according to their reliabilities. In the present study, human observers used active touch to judge the curvature of a shape. The curvature was specified by Positional and force Signals: When a finger slides across a surface, the finger's Position follows the surface geometry (Position Signal). At the same time, it is exposed to patterns of forces depending on the gradient of the surface (force Signal; Robles-de-la-Torre, G., & Hayward, V. (2001). Force can overcome object geometry in the perception of shape through active touch. Nature, 412, 445-448). We show that variations in the surface's material properties (compliance, friction) influence the sensorily available Position and force Signals, as well as the noise associated with these Signals. Along with this, material properties affect the weights given to the Position and force Signals for curvature judgements. Our findings are consistent with the notion of an observer who weights Signal estimates according to their reliabilities. That is, Signal weights shifted with the Signal noise, which in the present case resulted from active exploration.

  • Material Properties Determine How we Integrate Shape Signals in Active Touch
    2005
    Co-Authors: Knut Drewing, Marc O. Ernst, Thomas V. Wiecki
    Abstract:

    When sliding a finger across a bumpy surface, the finger follows the surface geometry (Position Signal). At the same time the finger is exposed to forces related to the slope of the surface (force Signal) [1]. For haptic shape perception the brain uses both Signals integrating them by weighted averaging [2]. This is consistent with the Maximum-Likelihood-Estimate (MLE) model on Signal integration, previously only applied to passive perception. The model further predicts that Signal weight is proportional to Signal reliability. Here, we tested this prediction for the integration of force and Position Signals to perceived curvature by manipulating material properties of the curve. Low as compared to high compliance decreased the reliability and so the weight of the sensorily transduced Position Signal. High as compared to low friction decreased the reliability and so the weight of the transduced force Signal. These results demonstrat that the MLE model extends to situations involving active touch.