Neuroscience: Pattern Recognition with Neural Networks
Retinal ganglion cells, that is, the output cells of the retina, have concentric on-center or off-center receptive fields. The on-center receptive field consists of an excitatory circular region surrounded by an inhibitory annular region, while the off-center receptive field has the opposite structure. These cells are supposed to extract contrast components from patterns projected onto the retina. Photoreceptors and ganglion cells are not...
วันอังคารที่ 24 มิถุนายน พ.ศ. 2557
08:58
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Psychology, Neurobiology and Modeling: The Science of Hebbian Reverberations
This chapter discusses introspective considerations for the necessity of having attractors, which neuropsychology has termed as reverberations. There exist experimental evidences for reverberations and attractors exist and are observable in neurophysiology. Attractors that are observed neurophysiologically, which appear to be required for mental processing, are very informative both for describing the functioning of...
08:56
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Neuroscience: Towards a Kinetic Theory of Cortical-like Neural Fields
The kinetic theory of neural fields is based fundamentally on the description of electrical properties of single neurons and on some statistical hypotheses about their connecting network. This chapter discusses the basis of this theory and its main results. It discusses a basilar, minimal set of biological neural features, except those linked to neural plasticity. Such characteristics are utilized for the construction, through...
08:55
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Neuroscience: Qualitative Overview of Population Neurodynamics
The estimates of the number of neurons in a cubic millimeter of cortex range from 104 to 106 and from 103 to 105 for the number of synaptic connections on each dendritic tree. The typical sensory input for a conditioned stimulus is carried by a parallel array of an immeasurably large number of receptor axons and the motor outflow for a typical conditioned response, a fraction of a second later, is carried in parallel by an immeasurably...
08:54
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Neuroscience:Noise and Chaos in Neural Systems
This chapter discusses two questions (1) how to characterize the dendritic arborization patterns and what could be the mechanism of the generation of dendritic branching trees and (2) what can be the role of environmental noise in the ontogenetic formation of ordered cortical structures. The dendritic arborization can be classified based on (1) randomness versus regularity in regard to branching of the various dendritic segments, resulting in a continuous...
08:53
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Neuroscience: Diffusion Models of Single Neurones' Activity
This chapter presents a survey of one-dimensional stochastic diffusion models for the membrane potential of a single neuron, with emphasis on the probabilistic properties of the models and on the related first-passage-time (FPT) problems, namely, on the determination of the neuronal output. It discusses how the much celebrated Ornstein-Uhlenbeck (OU) neuronal model can be obtained as the limit of a Markov process with discrete state...
08:52
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Neuroscience: Mechanisms Responsible for Epilepsy in Hippocampal Slices Predispose the Brain to Collective Oscillations
About 90% of the neurons in the CA3 region are pyramidal cells, the principal neurons that supply CA3 output to other parts of the brain (including, in particular, the CA1 hippocampal region and the opposite CA3 region—there is one hippocampus in each cerebral hemisphere). Of particular relevance to epilepsy and probably to normal brain function is the fact that CA3 neurons...
08:50
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Neuroscience: An Introduction to Neural Oscillators
Neurons and neural regions communicate to other cells and regions through a variety of means. The simplest means that is seen in early development is through gap junctions. The transport of ions or potential is done via diffusion resulting in a coupling term that depends on the difference between the two coupled entities. The most common communication is via chemical synapses. Other ways of communication are via pooled substances that can accumulate...
08:49
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Neuroscience:Single Neuron Dynamics: an Introduction
This chapter discusses the mathematical descriptions of neuronal behavior. The potential in the bath surrounding a neuron is relatively constant under normal circumstances, and it is conventionally taken to be zero. The potential inside the cell is then, by definition, the membrane potential. It can be measured by inserting a hollow glass electrode filled with an electrolytic solution through the cell membrane. At rest, the membrane potential...
08:41
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Neuroscience:Analysis of Single-Unit Activity in the Cerebral Cortex
The extracellular spiking activity of single units is usually recorded by inserting a very fine needle (micro-electrode) into the cortex while recording the voltage at the tip of the electrode. Living cells are characterized by having a potential difference across their membranes with the inside negative relative to the outside. Active nerve cells are characterized by having different membrane potential at different sites. Such...
08:36
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Neuroscience: Models of Visuomotor Coordination in Frog and Monkey
The escape direction in response to the approach of a large moving object may be briefly characterized as a compromise between the forward direction of the animal and the direction immediately away from the looming stimulus. Barriers can modify avoidance behavior, just as they modify approach behavior. If a barrier is interposed to block the preferred direction of escape for a stimulus coming from a particular direction, then the...
08:34
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Neuroscience:Anatomical Bases of Neural Network Modeling
Neuronal connectivity in most neural centers is sufficiently specific to permit the disassembly of the whole network into distinct pieces (or units) of characteristic internal connectivity that are arranged into larger structures by repetition of similar architectural units. These units have been termed neuronal modules and the architectural...
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