Recursos de colección

11th Joint Symposium on Neural Computation (31 recursos)

This is a closed subject based repository containing papers from this 2004 conference. Part of the Caltech Online Digital Archives (CODA) project.

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Mostrando recursos 1 - 20 de 30

  1. Spatial content of faces may be critical for individualizing faces

    Yue, Xiaomin; Biederman, Irving
    Many of the phenomena associated with face (vs. object) recognition can be understood in terms of a representation for individuating faces that retains aspects of the original spatial filter activations, as posited by Malsburg's Gabor Jet model that mimics the functions of the columns of V1 simple cells. Objects, in contrast, may be represented by a structural description specifying explicit relations among view invariant properties of edges of simple parts. Subjects judged whether a sequentially presented pair of images was the face of the same person, in one condition, or the same chair, in another (Biederman & Kalocsai, 1997). The images were filtered (in the Fourier domain)...

  2. Effects of Optic-Flow Density on the Metric Estimation of Rotation and Expansion

    Wurfel, Jeff D.; Barraza, Jose F.; Grzywacz, Norberto M.
    Optic flow generated by rigid surface patches can be decomposed into four elementary motion types. We have shown that the human visual system can metrically estimate two of these motion types, rotation and expansion, by angular velocity and rate of expansion respectively. However, this contradicts previous work that reported linear velocity to be the parameter estimated. This discrepancy was caused by a difference in experimental methods. Experimental evidence shows that the visual system uses a different motion parameter based on the amount of motion information available. We've modeled this systematic switchover in information utilized in a probabilistic manner. Specifically, low motion information stimuli...

  3. Use of correlation to assess the signal content of patterns of spike activity reflecting the population response of relays of the central auditorimotor system of cats

    Woody, C.D.
    Please see attached PDF

  4. Predicting EMG Activity from Neural Firing in M1 with Bayesian Backfitting

    Ting, Jo-Anne; D'Souza, Aaron; Schaal, Stefan
    Much attention has been given to directly interpreting neural firing in the primary motor cortex as a force signal, i.e., a signal that correlates with force production in muscles. How to robustly predict EMG patterns from M1 firing and which M1 neurons contribute to a particular muscle behaviour are interesting questions that arise under this hypothesis. From a statistical point of view, this question corresponds to analyzing datasets with a large number of input dimensions to detect which inputs contribute the most to the outputs. This is, at worst, a computationally exhausting combinatorial task. We present a Bayesian Backfitting algorithm that automatically determines the relevant input dimensions...

  5. Motion deficits in dyslexia are restricted to high external noise displays

    Sperling, Anne J.; Lu, Zhong-lin; Manis, Franklin R.
    Studies of motion perception in dyslexia have usually used random dot kinetograms with high external noise. Is the reported motion deficit in dyslexia due to deficiencies in motion perception per se, or due to deficiencies in excluding noise in the displays? In this study, we compared the motion perception thresholds of both dyslexic and nondyslexic children, and dyslexic and non-dyslexic adults using first-order coherent motion displays that varied in noise level and signal salience. Both dyslexic children and adults had higher motion thresholds than non-dyslexic children and adults when the task involved first-order motion processing in high noise. Dyslexics performed as well as non-dyslexics,...

  6. The Tsallis Entropy in the EEGs of Normal and Demented Individuals

    Sneddon, R.; Shankle, W.; Hara, J.; Fallon, J.; Saha, U.
    The electroencephalogram (EEG) is a recording of the brain's total electrical activity. Since the brain processes information, the information in the brain's total electrical activity probably corresponds to the information processing in the brain. This assumption was used to study the entropy or 'self-information' in the EEGs of participants who were performing a short-term memory task. There were two groups of participants in this study; one group had a medical diagnosis of "normal aging,"(Normal) and the other group had a diagnosis of "very mild dementia," (Dementia). The dementia diagnosis means that they have short-term memory impairment. The EEG of each...

  7. Recognizing Persons with One-Shot Learning

    Shah, Viral; Tang, Xiangyu; Garrett, Douglas; Kite, Lawrence; von der Malsburg, Christoph
    There have been several attempts to solve the problem of Human Recognition i.e. the ability to identify individual persons in novel situations. Using facial features (e.g. Wiskott et al, Facial Recognition using Elastic Bunch Graph Matching, 1997) for this purpose has proved to be quite successful. However when a person is at a appreciable distance, then the facial resolution is insufficient for reliable recognition. Therefore, some systems use additional information such as: Walking Patterns (Collins et al, Silhouette-based Human Identification from Body Shape and Gait, 2002) or distinguish color and shape features using Support Vector Machine classifiers (Nakajima et al, Full-body Person Recognition System,2003)....

  8. Factors contributing to Post-Traumatic Dentate Hyperexcitability: A Network Model Incorporating Topographic Connectivity Patterns

    Santhakumar, Vijayalakshmi; Soltesz, Ivan
    Head injury is a major risk factor in the etiology of temporal lobe epilepsy (TLE). Studies using a rodent model of concussive head trauma have identified specific patterns of cell loss and synaptic reorganization in the dentate gyrus after brain injury, which are similar to the changes in human TLE. However, the contribution of each of these cellular and synaptic alterations to increased excitability in the dentate neuronal circuits is not known. In order to independently examine the factors critical to post-traumatic dentate bhyperexcitability, we developed a reduced network model of the dentate gyrus with 500 granule cells, 15 mossy cells 6...

  9. Estimation of linear and nonlinear spatial receptive fields from natural Images

    Rapela, Joaquin; Grzywacz, Norberto M.
    Please see attached pdf

  10. Computational subunits in thin dendrites of pyramidal cells

    Polsky, Aloan; Mel, Bartlett W.; Schiller, Jackie
    The thin basal and oblique dendrites of cortical pyramidal neurons receive most of the cells' synaptic input, but their integrative properties remain uncertain. Previous studies have most often reported global linear or sublinear summation. An alternative view,supported by biophysical modeling studies, holds that thin dendrites provide a layer of independent computational 'subunits' that sigmoidally modulate their inputs prior to global summation. To distinguish these possibilities, we combined confocal imaging and dual-site focal synaptic stimulation of identified thin dendrites in rat neocortical pyramidal neurons. We found that nearby inputs on the same branch summed sigmoidally, whereas widely separated inputs or inputs to...

  11. Learning Motor Primitives with Reinforcement Learning

    Peters, Jan; Schaal, Stefan
    One of the major challenges in action generation for robotics and in the understanding of human motor control is to learn the "building blocks of move- ment generation," or more precisely, motor primitives. Recently, Ijspeert et al. [1, 2] suggested a novel framework how to use nonlinear dynamical systems as motor primitives. While a lot of progress has been made in teaching these mo- tor primitives using supervised or imitation learning, the self-improvement by interaction of the system with the environment remains a challenging problem. In this poster, we evaluate different reinforcement learning approaches can be used in order to improve the performance of motor primitives. For pursuing...

  12. What Can We Learn in Perceptual Learning?

    Padilla, Monica; Grzywacz, Norberto
    Please see attached pdf file

  13. Recognition of non face objects, designed to require the same stimulus processing as that for faces, show only minimal effects of differences in contrast polarity or orientation direction

    Nederhouser, Marissa; Mangini, Michael C.; Biederman, Irving
    Please see attached pdf

  14. A mathematical framework for the design and analysis of feature biasing strategies

    Navalpakkam, Vidhya; Itti, Laurent
    Please see attached pdf file.

  15. Object-based attention determines dominance in binocular rivalry

    Mitchell, Jude F.; Stoner, Gene R.; Reynolds, John H.
    See attached pdf file

  16. Perceptual decision influences V1 neuronal responses to ambiguous threedimensional objects

    Nadasdy, Zoltan; Pesaran, Bijan; Andersen, Richard A.
    We studied spike responses of V1 superficial layer neurons in a perceptual decision task. A rhesus monkey was trained to hold fixation during presentations of a three-dimensional (structure-from-motion) object and to make a perceptual decisions in an alternative choice paradigm while extracellular responses were obtained by single electrode penetrations. The disparity of constituent dots was varied from trial-to-trial to render perceptually ambiguous or unambiguous objects. Neurons with modulated disparity responses were selected. We estimated the certainty at which the firing rate of a given V1 neuron would allow an ideal observer to predict the monkey's perceptual choice in the task. Neuronal responses to zero-disparity (ambiguous) objects were sorted...

  17. A model of the mammalian muscle spindle

    Mileusnic, Milana; Loeb, Gerald E.
    Proprioceptors such as muscle spindles and Golgi tendon organs provide the central nervous system with sensory feedback for motor control and kinesthesia. It is difficult to record afferent activity from such receptors during motor behavior, so theories of motor control usually depend on implicit or explicit assumptions about such activity. The muscle spindle is the most important proprioceptor, playing a dominant role in kinesthesia and in reflexive adjustments to perturbations. Each muscle spindle accurately senses and encodes length and velocity information of the extrafusal muscle fibers over a wide range of movements despite the relatively restricted dynamic range of firing rates for action potentials. It does this by...

  18. Bayesian local directional accuracy of a directionally selective Ganglion-cell ensemble

    Merwine, David K.; Grzywacz, Noberto M.
    On-Off directionally selective ganglion cells (DSGC) of the rabbit retina send information about the direction of motion to the rest of the brain. Each of these cells responds best for motions in a preferred direction. There are four types of DSGC, each type preferring motions along one Cartesian axis (up, down, left or right). Every point in visual space is viewed by one cell of each type. We have measured the distribution of responses of DSGC as a function of contrast and direction of motion. With this information, and knowing the distribution of contrasts and directions of motion in natural images, we can apply Bayesian Analysis to...

  19. Geometric Analysis of the Axo-Dendritic Interface in Neocortical Pyramidal Neurons

    Mel, Bartlett W.; Bansal, Arjun K.
    Since the time of Hebb, the physical substrate for learning and memory in the brain has been most often discussed in relation to activity-dependent synaptic "weight" changes mediated by LTP or LTD. However, two recent theoretical studies suggest that long term information storage in neural tissue could also depend (heavily) on structural plasticity at the interface between axons and dendrites (Poirazi & Mel, 2001; Stepanyants et al. 2002). According to both theories, the capacity for structure-based information storage depends on the interaccessibility of afferent axons and their dendritic targets within the neuropil. For example, how many different axons are likely to be accessible to any...

  20. Timecourse and Temporal Dynamics of Attention in Visual/Auditory Central/Peripheral Cuing

    Lesmes, Luis A.; Lu, Zhong-Lin; Dosher, Barbara Anne
    Timecourse is a performance signature of attention systems 1. In this study, an attention reaction paradigm2 measures the timecourse of attention in visual central (VC), visual peripheral (VP), auditory central (AC), and auditory peripheral (AP) cuing of visual spatial attention. Observers viewed four synchronized letter streams at the corners of a 28 by 28 deg box, while fixating at the center. In each stream, an independent random permutation of 22 letters appeared at 10 /s. Observers were instructed to report the earliest three letters available from the target stream, with payoffs decreasing with cue-report SOA. Four types of cues were used: an...

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