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Proceedings of the 11th International Conference on neural Information Processing systems

作者： Reid R. Harrison Christof Koch Computation and Neural Systems Program California Institute of Technology Pasadena CA

Flies are capable of rapidly detecting and integrating visual motion information in behaviorly-relevant ways. The first stage of visual motion processing in flies is a retinotopic array of functional units known as elementary motion detectors (EMDs). Several decades ago, Reichardt and colleagues developed a correlation-based model of motion detection that described the behavior of these neural circuits. We have implemented a variant of this model in a 2.0-µm analog CMOS VLSI process. The result is a low-power, continuous-time analog circuit with integrated photoreceptors that responds to motion in real time. The responses of the circuit to drifting sinusoidal gratings qualitatively resemble the temporal frequency response, spatial frequency response, and direction selectivity of motion-sensitive neurons observed in insects. In addition to its possible engineering applications, the circuit could potentially be used as a building block for constructing hardware models of higher-level insect motion integration.

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Synaptic transmission: an information-theoretic perspective 97

Synaptic transmission: an information-theoretic perspective

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Proceedings of the 10th International Conference on neural Information Processing systems

作者： Amit Manwani Christof Koch Computation and Neural Systems Program California Institute of Technology Pasadena CA

Here we analyze synaptic transmission from an information-theoretic perspective. We derive closed-form expressions for the lower-bounds on the capacity of a simple model of a cortical synapse under two explicit coding paradigms. Under the "signal estimation" paradigm, we assume the signal to be encoded in the mean firing rate of a Poisson neuron. The performance of an optimal linear estimator of the signal then provides a lower bound on the capacity for signal estimation. Under the "signal detection" paradigm, the presence or absence of the signal has to be detected. Performance of the optimal spike detector allows us to compute a lower bound on the capacity for signal detection. We find that single synapses (for empirically measured parameter values) transmit information poorly but significant improvement can be achieved with a small amount of redundancy.

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Monotonic networks 97

Monotonic networks

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Proceedings of the 11th International Conference on neural Information Processing systems

作者： Joseph Sill Computation and Neural Systems program California Institute of Technology Pasadena CA

Monotonicity is a constraint which arises in many application domains. We present a machine learning model, the monotonic network, for which monotonicity can be enforced exactly, i.e., by virtue of functional form. A straightforward method for implementing and training a monotonic network is described. Monotonic networks are proven to be universal approximators of continuous, differentiable monotonic functions. We apply monotonic networks to a real-world task in corporate bond rating prediction and compare them to other approaches.

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computation and the single neuron

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NATURE 1997年第6613期385卷 207-210页

作者： Koch, C Computation and Neural Systems Program California Institute of Technology Pasadena California 91125 USA (e-mail: koch @klab. caltech. edu).

Neurons and their networks underlie our perceptions, actions and memories. The latest work on information processing and storage at the single-cell level reveals previously unimagined complexity and dynamism.

关键词： Adaptation, Physiological Animals Dendrites/physiology Nerve Net/physiology Neuronal Plasticity Neurons/physiology Synapses/physiology Time Factors

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Incorporating contextual information in white blood cell identification 97

Incorporating contextual information in white blood cell ide...

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Proceedings of the 11th International Conference on neural Information Processing systems

作者： Xubo Song Yaser Abu-Mostafa Joseph Sill Department of Electrical Engineering California Institute of Technology Pasadena CA Dept. of Electrical Engineering and Dept. of Computer Science California Institute of Technology Pasadena CA Computation and Neural Systems Program California Institute of Technology Pasadena CA

In this paper we propose a technique to incorporate contextual information into object classification. In the real world there are cases where the identity of an object is ambiguous due to the noise in the measurements based on which the classification should be made. It is helpful to reduce the ambiguity by utilizing extra information referred to as context, which in our case is the identities of the accompanying objects. This technique is applied to white blood cell classification. Comparisons are made against "no context" approach, which demonstrates the superior classification performance achieved by using context. In our particular application, it significantly reduces false alarm rate and thus greatly reduces the cost due to expensive clinical tests.

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Towards the neuronal correlate of visual awareness

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CURRENT OPINION IN NEUROBIOLOGY 1996年第2期6卷 158-164页

作者： Koch, C Braun, J Computation and Neural Systems Program 139-74 California Institute of Technology Pasadena California 91125 USA

Several encouraging developments towards identifying the neuronal correlate of visual awareness have emerged recently. Increasingly sophisticated behavioral paradigms permit the study of visual awareness in humans as well as in non-human primates. In patients with anatomically restricted lesions in striate and extrastriate cortex, highly informative deficits of visual awareness are observed. Similar deficits can be obtained in normal observers with a novel class of psychophysical displays. Taken together, these results suggest that the contents of visual awareness reflect neuronal activity in certain extrastriate, but not in striate, visual cortical areas.

关键词： Animals Awareness Brain Diseases Humans Neurons Reference Values Research Support U.S. Gov't Non-P.H.S. Visual Cortex Visual Perception

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Contribution of somatosensory cortex to responses in the rat cerebellar granule cell layer following peripheral tactile stimulation

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EXPERIMENTAL BRAIN RESEARCH 1996年第2期109卷 240-250页

作者： Morissette, J Bower, JM Computation and Neural Systems Program Caltech 216-76 California Institute of Technology Pasadena USA

The spatial coincidence of somatosensory cerebral cortex (SI) and trigeminal projections to the cerebellar hemisphere has been previously demonstrated. In this paper we describe the temporal relationship between tactilely-evoked responses in SI and in the granule cell layer of the cerebellar hemisphere, in anesthetized rats. We simultaneously recorded field potentials in areas of common receptive fields of SI and of the cerebellar folium crus IIa after peripheral tactile stimulation of the corresponding facial area. Response of the cerebellar granule cell layer to a brief tactile stimulation consisted of two components at different latencies. We found a strong correlation between the latency of the SI response and that of the second (long-latency) cerebellar component following facial stimulation. No such relationship was found between the latency of the SI response and that of the first (short-latency) cerebellar component, originating from a direct trigeminocerebellar pathway. In addition, lidocaine pressure injection in SI, cortical ablation, and decerebration all significantly affected the second cerebellar peak but not the first. Further, when tactile stimuli were presented 75 ms apart, the response in SI failed, as did the second cerebellar peak, while the short-latency cerebellar response still occurred. We found a wide spatial distribution of the upper lip response beyond the upper lip area in crus IIa for the long-latency component of the cerebellar response. Our results demonstrate that SI is the primary contributor to the cerebellar long-latency response to peripheral tactile stimulation. These results are discussed in the context of Purkinje cell responses to tactile input.

关键词： field potential timing lidocaine somatosensory cerebral cortex crus Ila mossy fiber cerebellum rat

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System implementations of analog VLSI velocity sensors

System implementations of analog VLSI velocity sensors

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International Conference on Microelectronics for neural Networks

作者： G. Indiveri J. Kramer C. Koch Computation and Neural Systems Program California California Institute of Technology Pasadena CA USA

We present three different architectures that make use of analog VLSI velocity sensors for detecting the focus of expansion, time to contact and motion discontinuities respectively. For each of the architectures proposed we describe the functionality of their component modules and their principles of operation. Data measurements obtained from the VLSI chips developed demonstrate their correct performance and their limits of operation.

关键词： Very large scale integration Sensor systems Optical sensors Image motion analysis Sensor arrays Motion detection Focusing Vehicles Computer architecture Image sensors

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A silicon model of the auditory neural perception of frequency modulated tones

A silicon model of the auditory neural perception of frequen...

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IEEE International Symposium on Circuits and systems (ISCAS)

作者： B.J. Arthur Computation and Neural Systems Program California Institute of Technology Pasadena CA USA

Frequency modulations in acoustic communication signals are thought to encode meaning in many animal species. Recent physiological experiments have elucidated possible neural mechanisms underlying their perception. The system described here attempts to model such mechanisms using subthreshold analog circuitry. It is built with a silicon cochlea and a unidirectional velocity-tuned delay line. Taps from the cochlea couple into the delay line. If the input frequency is modulated in the appropriate direction and right speed, the inputs to the delay line will coincide in time and summate. A similar design was recently used to detect motion in a vision chip.

关键词： Silicon Frequency modulation Delay lines Speech recognition Flexible manufacturing systems Circuits Motion detection Humans Filters Modulation coding

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Analog VLSI circuits for visual motion-based adaptation of post-saccadic drift

Analog VLSI circuits for visual motion-based adaptation of p...

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International Conference on Microelectronics for neural Networks

作者： T.K. Horiuchi C. Koch Computation and Neural Systems Program California Institute of Technology Pasadena CA USA

Using the analog VLSI-based saccadic eye movement system previously developed we investigate the use of biologically realistic error signals to calibrate the system in a manner similar to the primate oculomotor system. In this paper we introduce two new circuit components which are used to perform this task, a resettable-integrator model of the burst generator with a floating-gate structure to provide on-chip storage of analog parameters and a directionally-selective motion detector for detecting post-saccadic drift.

关键词： Very large scale integration Circuits Motion detection Muscles Detectors Eyes Humans Sockets Retina Biology computing

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