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Book Review : The Biology of Mind: Origins, Structures of Mind, Brain and Consciousness, by M. Deric Bownds

Trends in Neurosciences 2000年第5期23卷 229-230页

作者： Steven Quartz Division of Humanities and Social Sciences and Computation and Neural Systems Program California Institute of Technology Pasadena CA 91125 USA

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An analog VLSI implementation of a visual interneuron: enhanced sensory processing through biophysical modeling.

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International journal of neural systems 1999年第5期9卷 391-395页

作者： Harrison, R.R. Koch, C. Computation and Neural Systems Program California Institute of Technology harrison 91125 United States

Flies are capable of rapid, coordinated flight through unstructured environments. This flight is guided by visual motion information that is extracted from photoreceptors in a robust manner. One feature of the fly's visual processing that adds to this robustness is the saturation of wide-field motion-sensitive neuron responses with increasing pattern size. This makes the cell's responses less dependent on the sparseness of the optical flow field while retaining motion information. By implementing a compartmental neuronal model in silicon, we add this "gain control" to an existing analog VLSI model of fly vision. This results in enhanced performance in a compact, low-power CMOS motion sensor. Our silicon system also demonstrates that modern, biophysically-detailed models of neural sensory processing systems can be instantiated in VLSI hardware.

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Channel noise in excitable neuronal membranes 99

Channel noise in excitable neuronal membranes

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Proceedings of the 12th International Conference on neural Information Processing systems

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

Stochastic fluctuations of voltage-gated ion channels generate current and voltage noise in neuronal membranes. This noise may be a critical determinant of the efficacy of information processing within neural systems. Using Monte-Carlo simulations, we carry out a systematic investigation of the relationship between channel kinetics and the resulting membrane voltage noise using a stochastic Markov version of the Mainen-Sejnowski model of dendritic excitability in cortical neurons. Our simulations show that kinetic parameters which lead to an increase in membrane excitability (increasing channel densities, decreasing temperature) also lead to an increase in the magnitude of the subthreshold voltage noise. Noise also increases as the membrane is depolarized from rest towards threshold. This suggests that channel fluctuations may interfere with a neuron's ability to function as an integrator of its synaptic inputs and may limit the reliability and precision of neural information processing.

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Floating gate current mirror for gain correction in CMOS translinear circuits

Floating gate current mirror for gain correction in CMOS tra...

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IEEE International Symposium on Circuits and systems (ISCAS)

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

The exponential behaviour of MOSFETs in subthreshold operation has recently been exploited to build CMOS translinear circuits such as multipliers and log-domain filters. A major obstacle in developing a practical CMOS implementation is the variation in threshold voltage between devices. In translinear circuits, these voltage offsets manifest themselves as gain errors in the current-mode outputs. We have designed a floating-gate CMOS current mirror that can adapt its gain to compensate for these errors. The adaptation process uses only hot-electron injection, so the high voltages typically associated with tunneling are not needed. A small array of these circuits were fabricated in a standard 1.2 /spl mu/m double-poly CMOS process. We demonstrate gain adaptation and discuss the nonlinearity introduced by the adaptive mirror.

关键词： Mirrors Threshold voltage MOSFETs CMOS process CMOS technology Filters Secondary generated hot electron injection Current mode circuits Parasitic capacitance Tunneling

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Feature detection in analog VLSI 33

Feature detection in analog VLSI

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33rd Asilomar Conference on Signals, systems, and Computers, ACSSC 1999

作者： Pesavento, A. Koch, C. Dept. of Electr. Eng. California Inst. of Technol. PasadenaCA91125 United States Computation and Neural Systems Program California Institute of Technology PasadenaCA91125 United States

ISBN: (纸本)0780357000

Feature detection and tracking is a fundamental problem in computer vision research. By detecting and tracking features in an image sequence it is possible to recover information on both the motion of the viewer and the structure of the environment. We designed and tested a CMOS imager with analog VLSI focal plane computation for feature detection. The chip implements a feature detection algorithm that is suitable for integration in a compact analog VLSI chip. We review the algorithm, its analog VLSI implementation and results from the chip. © 1999 IEEE.

关键词： Feature extraction

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Feature detection in analog VLSI

Feature detection in analog VLSI

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Asilomar Conference on Signals, systems & Computers

作者： A. Pesavento C. Koch Department of Electrical Engineering California Institute of Technology Pasadena CA USA Computation and Neural Systems Program California Institute of Technology Pasadena CA USA

关键词： Computer vision Very large scale integration Eigenvalues and eigenfunctions Brightness Artificial intelligence Motion detection Analog computers Detection algorithms Frequency Ear

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An analog VLSI model of the fly elementary motion detector

An analog VLSI model of the fly elementary motion detector

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11th Annual Conference on neural Information Processing systems, NIPS 1997

作者： Harrison, Reid R. Koch, Christof Computation and Neural Systems Program 139-74 California Institute of Technology Pasadena CA 91125 United States

ISBN: (纸本)0262100762

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-/im analog CMOS VLSI process. The re-sult 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.

关键词： Frequency response

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Information maximization in single neurons 98

Information maximization in single neurons

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

作者： Martin Stemmler Christof Koch Computation and Neural Systems Program Caltech Pasadena CA

Information from the senses must be compressed into the limited range of firing rates generated by spiking nerve cells. Optimal compression uses all firing rates equally often, implying that the nerve cell's response matches the statistics of naturally occurring stimuli. Since changing the voltage-dependent ionic conductances in the cell membrane alters the flow of information, an unsupervised, non-Hebbian, developmental learning rule is derived to adapt the conductances in Hodgkin-Huxley model neurons. By maximizing the rate of information transmission, each firing rate within the model neuron's limited dynamic range is used equally often.

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Signal detection in noisy weakly-active dendrites 98

Signal detection in noisy weakly-active dendrites

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Proceedings of the 11th 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 derive measures quantifying the information loss of a synaptic signal due to the presence of neuronal noise sources, as it electrotonically propagates along a weakly-active dendrite. We model the dendrite as an infinite linear cable, with noise sources distributed along its length. The noise sources we consider are thermal noise, channel noise arising from the stochastic nature of voltage-dependent ionic channels (K+ and Na+) and synaptic noise due to spontaneous background activity. We assess the efficacy of information transfer using a signal detection paradigm where the objective is to detect the presence/absence of a presynaptic spike from the post-synaptic membrane voltage. This allows us to analytically assess the role of each of these noise sources in information transfer. For our choice of parameters, we find that the synaptic noise is the dominant noise source which limits the maximum length over which information be reliably transmitted.

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Floating-gate CMOS analog memory cell array

Floating-gate CMOS analog memory cell array

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IEEE International Symposium on Circuits and systems (ISCAS)

作者： R.R. Harrison P. Hasler B.A. Minch Computation and Neural Systems Program 139-74 California Institute of Technology NASA Pasadena CA USA Department of Electrical and Computer Engineering Georgia Institute of Technology Atlanta GA USA School of Electrical Engineering Cornell University Ithaca NY USA

The complexity of analog VLSI systems is often limited by the number of pins on a chip rather than by the die area. Currently, many analog parameters and biases are stored off chip. Moving parameter storage on chip could save pins and allow us to create complex programmable analog systems. In this paper, we present a design for an on-chip non-volatile analog memory cell that can be configured in addressable arrays and programmed easily. We use floating-gate MOS transistors to store charge, and we use the processes of tunneling and hot-electron injection to program values. We achieve greater than 13-bit precision with no crosstalk between memory cells.

关键词： Nonvolatile memory Analog memory Pins Voltage Potentiometers Tunneling Very large scale integration Secondary generated hot electron injection Analog computers CMOS technology

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