A system is being developed to study how the retina processes, encodes and communicates information about the visual world to the brain. It will image the activity of retinal output neurons over a region of live retin...
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A system is being developed to study how the retina processes, encodes and communicates information about the visual world to the brain. It will image the activity of retinal output neurons over a region of live retina approaching that used for significant neural computation in the visual cortex. A prototype system consisting of 61 microelectrodes, covering an area of 0.17 mm(2), is described, including some first results with monkey retina. The plans and status for a system with 512 microelectrodes, covering an area of 1.7 mm(2), are also given. (C) 2002 Elsevier Science B.V. All rights reserved.
We present a method to estimate the neuronal firing rate from single-trial spike trains. The method, based on convolution of the spike train with a fixed kernel function, is calibrated by means of simulated spike trai...
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We present a method to estimate the neuronal firing rate from single-trial spike trains. The method, based on convolution of the spike train with a fixed kernel function, is calibrated by means of simulated spike trains for a representative selection of realistic dynamic rate functions. We derive rules for the optimized use and performance of the kernel method, specifically with respect to an effective choice of the shape and width of the kernel functions. An application of our technique to the on-line, single-trial reconstruction of arm movement trajectories from multiple single-unit spike trains using dynamic population vectors illustrates a possible use of the proposed method. (C) 1999 Elsevier Science B.V. All rights reserved.
This article presents an alternative phase coding mechanism for Freeman's KIII model of population neurodynamics. Motivated by experimental evidence that supports the existence of a neural code based on synchronou...
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This article presents an alternative phase coding mechanism for Freeman's KIII model of population neurodynamics. Motivated by experimental evidence that supports the existence of a neural code based on synchronous oscillations, we propose an analogy between synchronization in neural populations and phase locking in KIII channels. An efficient method is proposed to extract phase differences across granule channels from their state-space trajectories. First, the scale invariance of the KIII model with respect to phase information is established. The phase code is then compared against the conventional amplitude code in terms of their bit-wise and across-fiber pattern recovery capabilities using decision-theoretic principles and a Hamming-distance classifier. Graph isomorphism in the Hebbian connections is exploited to perform an exhaustive evaluation of patterns on an 8-channel KIII model. Simulation results show that phase information outperforms amplitude information in the recovery of incomplete or corrupted stimuli. (C) 2003 Elsevier Science Ltd. All rights reserved.
Numerous theories of neural processing, often motivated by experimental observations, have explored the computational properties of neural codes based on the absolute or relative timing of spikes in spike trains. Spik...
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Numerous theories of neural processing, often motivated by experimental observations, have explored the computational properties of neural codes based on the absolute or relative timing of spikes in spike trains. Spiking neuron models and theories however, as well as their experimental Counterparts, have generally been limited to the simulation or observation of isolated neurons, isolated spike trains, or reduced neural Populations. Such theories would therefore seem inappropriate to capture the properties of a neural code relying on temporal spike patterns distributed across large neuronal Populations. Here we report a range of computer simulations and theoretical considerations that were designed to explore the possibilities of one such code and its relevance for visual processing. In a unified framework where the relation between Stimulus saliency and spike relative timing plays the central role, we describe how the ventral stream of the visual system could process natural input scenes and extract meaningful information, both rapidly and reliably. The first wave of spikes generated in the retina in response to a visual stimulation carries information explicitly in its spatio-temporal structure: the most salient information is represented by the first spikes over the population. This spike wave. propagating through a hierarchy of visual areas, is regenerated at each processing stage, where its temporal Structure can be modified by (i) the selectivity of the cortical neurons, (ii) lateral interactions and (iii) top-down attentional influences from higher order cortical areas. The resulting model could account for the remarkable efficiency and rapidity of processing observed in the primate visual system. (C) 2002 Elsevier Science Ltd. All rights reserved.
Oral temperature is a component and modifier of taste perception. Both trigeminal (V) and taste-sensitive cells, including those in the nucleus of the solitary tract (NTS), can respond to oral temperature. However, fu...
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Oral temperature is a component and modifier of taste perception. Both trigeminal (V) and taste-sensitive cells, including those in the nucleus of the solitary tract (NTS), can respond to oral temperature. However, functional associations in thermal sensitivity between V and gustatory neurons are poorly understood. To study this we recorded electrophysiological responses to oral stimulation with cool (9, 15, 25, 32, and 34 A degrees C) and warm (40 and 45 A degrees C) temperatures from medullary V (n = 45) and taste-sensitive NTS (n = 27) neurons in anesthetized mice. Results showed temperatures below 34 A degrees C activated the majority of V neurons but only a minority of NTS units. V neurons displayed larger responses to cooling and responded to temperatures that poorly stimulated NTS cells. Multivariate analyses revealed different temperatures induced larger differences in responses across V compared with NTS neurons, indicating V pathways possess greater capacity to signal temperature. Conversely, responses to temperature in NTS units associated with gustatory tuning. Further analyses identified two types of cooling-sensitive V neurons oriented toward innocuous or noxious cooling. Multivariate analyses indicated the combined response of these cells afforded distinction among a broad range of cool temperatures, suggesting multiple types of V neurons work together to represent oral cooling.
The mammalian retina engages a broad array of linear and nonlinear circuit mechanisms to convert natural scenes into retinal ganglion cell (RGC) spike outputs. Although many individual integration mechanisms are well ...
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The mammalian retina engages a broad array of linear and nonlinear circuit mechanisms to convert natural scenes into retinal ganglion cell (RGC) spike outputs. Although many individual integration mechanisms are well understood, we know less about how multiple mechanisms interact to encode the complex spatial features present in natural inputs. Here, we identified key spatial features in natural scenes that shape encoding by primate parasol RGCs. Our approach identified simplifications in the spatial structure of natural scenes that minimally altered RGC spike responses. We observed that reducing natural movies into 16 linearly integrated regions described similar to 80% of the structure of parasol RGC spike responses;this performance depended on the number of regions but not their precise spatial locations. We used simplified stimuli to design high-dimensional metamers that recapitulated responses to naturalistic movies. Finally, we modeled the retinal computations that convert flashed natural images into one-dimensional spike counts.
The time required for rats to make a behavioral taste discrimination was predicted from neural discharge rates and tested using conditioned aversion. Predictions were based on the hypothesis that the responses evoked ...
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The time required for rats to make a behavioral taste discrimination was predicted from neural discharge rates and tested using conditioned aversion. Predictions were based on the hypothesis that the responses evoked from a neural population by two different chemicals must diverge by a certain critical total number of spikes before the chemicals are discriminable. This total could be derived from the responses of all neurons in the population. Behavioral discrimination times generally supported predictions made from second-order (bulbar) neural responses, but were ambiguous concerning predictions based on fourth-order (thalamic) responses. The implications of these results for the possible functions of bulbar and thalamic taste neurons is discussed.
Several motion-detection models have been proposed based on insect visual system studies. We specifically examine two models, the Hassenstein-Reichardt (HR) model and the two-detector (2D) model, before selecting mode...
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ISBN:
(纸本)9783319700908;9783319700892
Several motion-detection models have been proposed based on insect visual system studies. We specifically examine two models, the Hassenstein-Reichardt (HR) model and the two-detector (2D) model, before selecting model the more efficient motion encoders. We analytically obtained the mean and variance of stationary responses of the HR and the 2D models to white noise to evaluate performances of the two models. Especially when analyzing the 2D model, we calculated higher-order cumulants of a rectified Gaussian. Results show that the 2D model gives almost equal performance to that of the HR model in a biologically reasonable case.
The intensity of analog stimuli, such as the loudness of sounds, is converted by our biological sensory systems into short duration electrical pulses in nerve fibres. These pulses are known as action potentials. In ma...
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ISBN:
(纸本)9780819469700
The intensity of analog stimuli, such as the loudness of sounds, is converted by our biological sensory systems into short duration electrical pulses in nerve fibres. These pulses are known as action potentials. In many cases, the transduction process that converts stimulus intensity into an action-potential encoding introduces significant randomness that appears to reduce the quality of the encoding. Due to this inherent random noise, it is the average rate at which action potentials are produced, rather than the instantaneous rate, that encodes stimulus amplitude. In this paper the limits of performance of this transduction process are analyzed using an information theoretic perspective of neural rate coding.
Odor information is coded in the insect brain in a sequence of steps, ranging from the receptor cells, via the neural network in the antennal lobe, to higher order brain centers, among which the mushroom bodies and th...
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Odor information is coded in the insect brain in a sequence of steps, ranging from the receptor cells, via the neural network in the antennal lobe, to higher order brain centers, among which the mushroom bodies and the lateral horn are the most prominent. Across all of these processing steps, coding logic is combinatorial, in the sense that information is represented as patterns of activity across a population of neurons, rather than in individual neurons. Because different neurons are located in different places, such a coding logic is often termed spatial, and can be visualized with optical imaging techniques. We employ in vivo calcium imaging in order to record odor-evoked activity patterns in olfactory receptor neurons, different populations of local neurons in the antennal lobes, projection neurons linking antennal lobes to the mushroom bodies, and the intrinsic cells of the mushroom bodies themselves, the Kenyon cells. These studies confirm the combinatorial nature of coding at all of these stages. However, the transmission of odor-evoked activity patterns from projection neuron dendrites via their axon terminals onto Kenyon cells is accompanied by a progressive sparsening of the population code. Activity patterns also show characteristic temporal properties. While a part of the temporal response properties reflect the physical sequence of odor filaments, another part is generated by local neuron networks. In honeybees, gamma-aminobutyric acid (GABA)-ergic and histaminergic neurons both contribute inhibitory networks to the antennal lobe. Interestingly, temporal properties differ markedly in different brain areas. In particular, in the antennal lobe odor-evoked activity develops over slow time courses, while responses in Kenyon cells are phasic and transient. The termination of an odor stimulus is reflected by a decrease in activity within most glomeruli of the antennal lobe and an off-response in some glomeruli, while in the mushroom bodies about half of the
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