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coding OF FREE FIELD INTENSITY IN THE AUDITORY MIDBRAIN OF THE LEOPARD FROG .1. RESULTS FOR TONAL STIMULI

HEARING RESEARCH 1989年第1-2期40卷 147-165页

作者： EGGERMONT, JJ Behavioral Neuroscience Research Group Department of Psychology The University of Calgary Calgary Alberta Canada

Single unit recordings in the auditory midbrain of the leopard frog were obtained in response to free field, random frequency, tone pip stimulation. Five sequences of 81 logarithmically distributed frequencies from 100 Hz to 3200 Hz inclusive at stimulus levels between 94 dB SPL and the unit''s threshold were presented. Sigmoidal response-intensity functions were fit through the data points for monotonic and nearly monotonic unit (53 in total) at all frequencies for which the units were responsive. From the fitcures a generalized slope and inflection point were obtained and converted into a dynamic range and a threshold value. Single unit dynamic ranges at CF frequencies were between 5 and 80 dB, and thresholds were between 20 dB and 90 dB. For the population of units the dynamic ranges were positively correlated with the threshold values. A population response was computed by adding the response at each intensity-frequency combination, and again curve fitting with the sigmoidal function. The population dynamic range was about 70 dB for the basilar papilla range (around 1200 Hz) and somewhat less, about 45 dB, for the amphibian papilla neurons. The amount of synchronization of the firings of the individual units with the stimulus was calculated on basis of the shifted auto-coincidence function. The stimulus synchronization appeared to be largely independent of stimulus intensity. Inter-neuron synchronization was computed on basis of the cross-coincidence function of two neuronal spike trains. Also this synchronization was stimulus independent. It was concluded that synchronization or other forms of multiplicative action cannot on its own code for stimulus intensity. From the appliction of signal detection theory it is concluded that a rate coding on basis of a modest population of units has an acceptable dynamic range, roughly covering 30-100 dB SPL, produces a more than adequate sensitivity for intensity differences and may be used as a code for intensity.

关键词： Auto-correlation Cross-correlation Frog Intensity-coding population coding Rate-coding Single unit coding Synchrony-coding Torus semicircularis

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Real-time simulation of large-scale neural architectures for visual features computation based on GPU

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NETWORK-COMPUTATION IN NEURAL SYSTEMS 2012年第4期23卷 272-291页

作者： Chessa, Manuela Bianchi, Valentina Zampetti, Massimo Sabatini, Silvio P. Solari, Fabio Univ Genoa Dept Informat Bioengn Robot & Syst Engn I-16145 Genoa Italy

The intrinsic parallelism of visual neural architectures based on distributed hierarchical layers is well suited to be implemented on the multi-core architectures of modern graphics cards. The design strategies that allow us to optimally take advantage of such parallelism, in order to efficiently map on GPU the hierarchy of layers and the canonical neural computations, are proposed. Specifically, the advantages of a cortical map-like representation of the data are exploited. Moreover, a GPU implementation of a novel neural architecture for the computation of binocular disparity from stereo image pairs, based on populations of binocular energy neurons, is presented. The implemented neural model achieves good performances in terms of reliability of the disparity estimates and a near real-time execution speed, thus demonstrating the effectiveness of the devised design strategies. The proposed approach is valid in general, since the neural building blocks we implemented are a common basis for the modeling of visual neural functionalities.

关键词： Visual neural model population coding binocular energy model disparity computation GPGPU

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Eye position encoding in the macaque posterior parietal cortex

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EUROPEAN JOURNAL OF NEUROSCIENCE 1998年第1期10卷 153-160页

作者： Bremmer, F Pouget, A Hoffmann, KP Ruhr Univ Bochum Dept Zool & Neurobiol D-44780 Bochum Germany Georgetown Inst Cognit & Computat Sci Washington DC 20007 USA

In two previous studies, we had demonstrated the influence of eye position on neuronal discharges in the middle temporal area, medial superior temporal area, lateral intraparietal area and area 7A of the awake monkey (Bremmer et al., 1997a,b), Eye position effects also have been found in visual cortical areas V3A and V6 and even in the premotor cortex and the supplementary eye field. These effects are generally discussed in light of a coordinate transformation of visual signals into a non-retinocentric frame of reference. Neural network studies dealing with the eye position effect succeeded in constructing such non-retinocentric representations by using model neurones whose response characteristics resembled those of 'real' neurones. However, to our knowledge, response properties of real neurones never acted as input into these neural networks. In the present study, we thus investigated whether, theoretically, eye position could be estimated from the population discharge of the (previously) recorded neurones and, if so, we intended to develop an encoding algorithm for the position of the eyes in the orbit. The optimal linear estimator proved the capability of the ensemble activity for determining correctly eye position. We then developed the so-called subpopulation encoding of eye position. This algorithm is based on the partition of the ensemble of neurones into two pairs of subpopulations. Eye position is represented by the differences of activity levels within each pair of subpopulations. Considering this result, encoding of the location of an object relative to the head could easily be accomplished by combining eye position information with the intrinsic knowledge about the retinal location of a visual stimulus. Taken together, these results show that throughout the monkey's visual cortical system information is available which can be used in a fairly simple manner in order to generate a non-retinocentric representation of visual information.

关键词： eye position effect non-retinocentric space representation population coding modelling

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Prey detection mechanism of elasmobranchs

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BIOSYSTEMS 2007年第2-3期87卷 322-331页

作者： Kim, DaeEun Univ Leicester Leicester LE1 7RH Leics England

Elasmobranchs can detect a little amount of electric fields and they have characteristic approach strategies to find an electric dipole source generated by prey or conspecifics. They appear to align the body at a constant angle with the current flow line of the electric field while swimming towards prey. However, it has not been studied how they process the perception of electric fields for the approach behaviour or what kind of neural mechanism is used. We use a model of electrosensory perception with electrodynamics and explore a possible approach mechanism based on the sensory landscape distributed on electroreceptors. This paper presents that elasmobranchs can estimate the direction of the electric field by swaying their head, which will be a basis information for their particular approach behaviour. A velocity profile of voltage gradients and intensity difference among the ampullary clusters can be another cues to detect a prey source. (c) 2006 Elsevier Ireland Ltd. All rights reserved.

关键词： elasmobranch fish electrosensory system approach behaviour bioelectric field prey capture population coding

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Understanding the computation of time using neural network models

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PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2020年第19期117卷 10530-10540页

作者： Bi, Zedong Zhou, Changsong Qingdao Univ Inst Future Qingdao 266071 Shandong Peoples R China Hong Kong Baptist Univ Dept Phys Kowloon Tong Hong Kong Peoples R China Hong Kong Baptist Univ Ctr Nonlinear Studies Kowloon Tong Hong Kong Peoples R China Hong Kong Baptist Univ Inst Computat & Theoret Studies Kowloon Tong Hong Kong Peoples R China Hong Kong Baptist Univ Res Ctr Inst Res & Continuing Educ Shenzhen 51800 Peoples R China Beijing Computat Sci Res Ctr Beijing 100193 Peoples R China Zhejiang Univ Dept Phys Hangzhou 310027 Peoples R China

To maximize future rewards in this ever-changing world, animals must be able to discover the temporal structure of stimuli and then anticipate or act correctly at the right time. How do animals perceive, maintain, and use time intervals ranging from hundreds of milliseconds to multiseconds in working memory? How is temporal information processed concurrently with spatial information and decision making? Why are there strong neuronal temporal signals in tasks in which temporal information is not required? A systematic understanding of the underlying neural mechanisms is still lacking. Here, we addressed these problems using supervised training of recurrent neural network models. We revealed that neural networks perceive elapsed time through state evolution along stereotypical trajectory, maintain time intervals in working memory in the monotonic increase or decrease of the firing rates of interval-tuned neurons, and compare or produce time intervals by scaling state evolution speed. Temporal and nontemporal information is coded in subspaces orthogonal with each other, and the state trajectories with time at different nontemporal information are quasiparallel and isomorphic. Such coding geometry facilitates the decoding generalizability of temporal and nontemporal information across each other. The network structure exhibits multiple feedforward sequences that mutually excite or inhibit depending on whether their preferences of nontemporal information are similar or not. We identified four factors that facilitate strong temporal signals in nontiming tasks, including the anticipation of coming events. Our work discloses fundamental computational principles of temporal processing, and it is supported by and gives predictions to a number of experimental phenomena.

关键词： interval timing population coding neural network model

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The minimum information principle and its application to neural code analysis

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PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2009年第9期106卷 3490-3495页

作者： Globerson, Amir Stark, Eran Vaadiab, Eilon Tishby, Naftali Hebrew Univ Jerusalem Sch Engn & Comp Sci IL-91904 Jerusalem Israel Hebrew Univ Jerusalem Hadassah Med Sch Dept Physiol IL-91120 Jerusalem Israel Hebrew Univ Jerusalem Interdisciplinary Ctr Neural Computat IL-91904 Jerusalem Israel

The study of complex information processing systems requires appropriate theoretical tools to help unravel their underlying design principles. Information theory is one such tool, and has been utilized extensively in the study of the neural code. Although much progress has been made in information theoretic methodology, there is still no satisfying answer to the question: "What is the information that a given property of the neural population activity (e.g., the responses of single cells within the population) carries about a set of stimuli?" Here, we answer such questions via the minimum mutual information (MinMI) principle. We quantify the information in any statistical property of the neural response by considering all hypothetical neuronal populations that have the given property and finding the one that contains the minimum information about the stimuli. All systems with higher information values necessarily contain additional information processing mechanisms and, thus, the minimum captures the information related to the given property alone. MinMI may be used to measure information in properties of the neural response, such as that conveyed by responses of small subsets of cells (e.g., singles or pairs) in a large population and cooperative effects between subunits in networks. We show how the framework can be used to study neural coding in large populations and to reveal properties that are not discovered by other information theoretic methods.

关键词： neural coding information theory maximum entropy population coding

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Neuromodulation of Attention

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NEURON 2018年第4期97卷 769-785页

作者： Thiele, Alexander Bellgrove, Mark A. Newcastle Univ Inst Neurosci Newcastle Upon Tyne Tyne & Wear England Monash Univ MICCN Melbourne Vic Australia Monash Univ Sch Psychol Sci Melbourne Vic Australia

Attention is critical to high-level cognition and attention deficits are a hallmark of neurologic and neuropsychiatric disorders. Although years of research indicates that distinct neuromodulators influence attentional control, amechanistic account that traverses levels of analysis (cells, circuits, behavior) is missing. However, such an account is critical to guide the development of next-generation pharmacotherapies aimed at forestalling or remediating the global burden associated with disorders of attention. Here, we summarize current neuroscientific understanding of how attention affects single neurons and networks of neurons. We then review key results that have informed our understanding of how neuromodulation shapes these neuron and network properties and thereby enables the appropriate allocation of attention to relevant external or internal events. Finally, we highlight areas where we believe hypotheses can be formulated and tackled experimentally in the near future, thereby critically increasing our mechanistic understanding of how attention is implemented at the cellular and network levels.

关键词： attention pharmacology top-down neuromodulators attractor networks population coding

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Cortical pooling algorithms for judging global motion direction

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PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2007年第9期104卷 3532-3537页

作者： Webb, Ben S. Ledgeway, Timothy McGraw, Paul V. Univ Nottingham Visual Neurosci Grp Sch Psychol Nottingham NG7 2RD England

Physiological studies suggest that decision networks read from the neural representation in the middle temporal area to determine the perceived direction of visual motion, whereas psychophysical studies tend to characterize motion perception in terms of the statistical properties of stimuli. To reconcile these different approaches, we examined whether estimating the central tendency of the physical direction of global motion was a better indicator of perceived direction than algorithms (e.g., maximum likelihood) that read from directionally tuned mechanisms near the end of the motion pathway. The task of human observers was to discriminate the global direction of random dot kinematograms composed of asymmetrical distributions of local directions with distinct measures of central tendency. None of the statistical measures of image direction central tendency provided consistently accurate predictions of perceived global motion direction. However, regardless of the local composition of motion directions, a maximum-likelihood decoder produced global motion estimates commensurate with the psychophysical data. Our results suggest that mechanism-based, read-out algorithms offer a more accurate and robust guide to human motion perception than any stimulus-based, statistical estimate of central tendency.

关键词： human psychophysics MT/V5 read-out algorithms visual motion population coding

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Communication call-evoked gamma-band activity in the auditory cortex of awake bats is modified by complex acoustic features

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BRAIN RESEARCH 2008年第1期1188卷 76-86页

作者： Medvedev, Andrei V. Kanwal, Jagmeet S. Georgetown Univ Med Ctr Dept Phys & Biophys Washington DC 20057 USA

Mustached bats emit an acoustically rich variety of calls for social communication. In the posterior primary auditory cortex, activity of neural ensembles measured as local field potentials (LFPs) can uniquely encode each call type. Here we report that LFPs recorded in response to calls contain oscillatory activity in the gamma-band frequency range (> 20 Hz). The power spectrum of these high-frequency oscillations shows either two peaks of energy (at 40 Hz and 100 Hz), or just one peak at 40 Hz. The relative power of gamma-band activity in the power spectrum of a call-evoked UP correlates significantly with the 'harmonic complexity' of a call. Gamma-band activity is attenuated with reversal of frequency-modulated calls. Amplitude modulation, even when asymmetric across call reversals, has no significant effect on gamma-band activity. These results provide the first experimental evidence that complex features within different groups of species-specific calls modify the power spectrum of evoked gamma-band activity. (c) 2007 Elsevier B.V. All rights reserved.

关键词： speech music gamma-band oscillations synchrony temporal coding population coding binding hearing auditory processing sensory and motor systems

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Theoretical analysis of a time-frequency-PCNN auditory cortex model

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INTERNATIONAL JOURNAL OF NEURAL SYSTEMS 2005年第5期15卷 339-347页

作者： Volkmer, M Hamburg Univ Technol Dept Distributed Syst D-21073 Hamburg Germany

A particular pulsed neural model of the auditory cortex, the Time-Frequency Pulse Coupled Neural Network (TF-PCNN), has shown to decompose its stimulus from the cochlea into characteristic pulse-coded time-frequency (TF) stop and pass regions. A derived sum of spectrograms representation with these zero- or one-valued TF weightings has already been applied for the denoising of speech in a previous work. This decomposition is now related to the concept of TF projection filters, which allows to reinterpret the model equations. The functionality imposed by the model equations can so be accessed and justified from a TF signal processing perspective, in addition to its biological motivation from experimentally observed neurophysiological behavior and simulations.

关键词： pulsed neural networks time-frequency analysis spectro-temporal receptive fields population coding sparse neural code

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