Principles of Sensory Coding

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● Principles of Sensory Coding
● What do Sensory Systems Sense?
● How are these attributes represented in the brain?
● Getting Sense Input into the CNS
● Sensory Transduction
● Coding of sensory input
● Other Possible Neural Codes 1
● Other Possible Neural Codes 2
● Coding with Bursts of Spikes:
Salient Sensory Input
● Coding with Bursts of Spikes:
Reward Associated Signals
● Receptive Fields
● The Overall Plan of Sensory Systems
● Parallel Pathways for General and Communication Signals
● The Somatosensory System
● Exteroreceptors 1
● Exteroreceptors 2
● Central Projections of Exteroreceptors
● The Spinothalamic System
● The Spinothalamic System 2
● The Dorsal Column, Medial Lemniscal Fine Touch System
● The Dorsal Column, Medial Lemniscal Fine Touch System 2
● The Dorsal Column, Medial Lemniscal Fine Touch System 3
● The Dorsal Column, Medial Lemniscal Fine Touch System 4
● The Dorsal Column, Medial Lemniscal Fine Touch System 5
● The Rodent Vibrissae System:
A Model System for the Study of Active Touch
● The Vibrissae Sense can Encode Texture
● The Vibrissae Sensory System uses many encoding Schemes

نوع زبان: انگلیسی حجم: 5.73 مگا بایت
نوع فایل: اسلاید پاورپوینت تعداد اسلایدها: 32 صفحه
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گروه موضوعی: زمان استخراج مطلب: 2019/05/16 04:30:33

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., sensory, system, input, signal, stimulus, brain, estimate, neuron, spike, neural, feature,

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عبارات پرتکرار و مهم در این اسلاید عبارتند از: ., sensory, system, input, signal, stimulus, brain, estimate, neuron, spike, neural, feature,

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principles of sensory coding sensory systems appear to be very diverse. yet they all solve the same task they convert environmental signals into neural activity that can influence the motor system of the animal. the plan for this section of the course is to first give an overview of what sensory systems do in general and then to focus on the operation of the classic senses of vertebrates. methods for studying sensory processing psychophysics use behavioral testing to establish the sensitivity of a sensory system and the rules of its operation. electrophysiological recording from the single neurons or small groups of neurons along the sensory pathway to find out how the neural circuitry gives rise to the perceptual abilities. imaging in humans that are doing perceptual tasks to identify the brain areas responsible. what do sensory systems sense there are two main functions of any sensory system the detection of a signal. weak signals can be detected without the animal being able to finely discriminate any of its features. discrimination of some aspects of a sensory input. this is often referred to as estimation. what must be estimated from the input ۱. qualitative features such as colour or odorant this is often referred to as modality what is it ۲. quantitative features such as magnitude often referred to as the intensity of a stimulus ۳. temporal features such as duration or frequency of a signal ۴. spatial location of a stimulus where is it typically all these aspects are estimated at once. a common strategy of sensory systems is to have separate neural pathways specialized for estimating different types of stimulus features. for example the visual system analyzes colour shape and movement in different brain regions. how are these attributes represented in the brain modality the most basic mechanism for identifying the nature of a sensory input is via labeled lines. what this means is that input from the optic nerve is always interpreted by the brain as visual input etc. this extends to much finer discriminations the connections of pain and touch fibers in the somatosensory system are entirely different and electrical stimulation of either leads to the appropriate sensation. intensity the estimated intensity of a stimulus is not a linear function of the actual intensity. as shown in the graph below the relation can be described as logarithmic or power law. the reason is intuitively easy to understand. increases of a weak signal generate a larger perceived increase than increases of a strong signal the percept saturates. a power law relation best describes the relation between stimulus strength and perceived stimulus intensity. kandel schwartz and jessel temporal features onset time andduration. the duration of a stimulus is estimated from the onset of the neural response and its duration. typically there are neurons in sensory systems that only respond to the onset of a stimulus these are generally referred to as phasic responders and they are good for estimating the time of occurrence of a signal. there are other neurons that respond throughout the stimulus presentation tonic responders these signal stimulus duration. frequency. the frequency of a signal may be very important is some senses audition . there are several ways to estimate this one way is to make the neural response precisely time locked to the signal. kandel et al. bear et al. location. a common principle is used for estimating where a stimulus is located topographic mapping. this means that points close together on the sensory surface are represented close together in the brain. in the somatosensory surface this is called somatotopy in the visual system retinotopy and in the auditory system tonotopy . skin regions that are close together are mapped to adjacent regions of the cerebral cortex. bear et al. getting sense input into the cns sensory input comes in many flavours. information in the cns all comes in the same currency action potentials or spikes. the reason that the cns uses only one way to transmit information is simple it allows integration of different types sensory input and the connection of sensory input to motor output all the neurons dealing with these different systems use the same language of spikes. the problem becomes how to translate the different kinds of sensory input into spikes. in all cases this is done by specialized receptor cells or parts of cells in a process called sensory transduction. the transduction process depends on the nature of the signal. chemoreception. mechanoreception. vibration reception. light. the initial transduction process causes the receptor cell to depolarize and this leads to spike initiation in sensory afferent fibers that then convey this information to the brain. sensory transduction stretch gated channels in the nerve terminal of an afferent fiber open and cause it to discharge. the fiber projects to the cns. a chemical binds to the receptors on an afferent process causes depolarization and discharge. a hair cell is activated by vibration becomes depolarized and releases transmitter. the transmitter excites an afferent fiber it discharges and this information reaches the cns. a photoreceptor is activated by light its release of transmitter is reduced. after a series of complex interactions in the retina ganglion cells discharge and send this information to the brain. the most important point is that the message sent by a receptor to the brain is in the form of a sequence of spikes a spike train. what is this message kandel et al. coding of sensory input all sensory input is represented in the firing patterns of populations of neurons. this is the most remarkable conclusion of sensory physiology. the representation is referred to as a population neural code. …

کلمات کلیدی پرکاربرد در این اسلاید پاورپوینت: ., sensory, system, input, signal, stimulus, brain, estimate, neuron, spike, neural, feature,

این فایل پاورپوینت شامل 32 اسلاید و به زبان انگلیسی و حجم آن 5.73 مگا بایت است. نوع قالب فایل ppt بوده که با این لینک قابل دانلود است. این مطلب برگرفته از سایت زیر است و مسئولیت انتشار آن با منبع اصلی می باشد که در تاریخ 2019/05/16 04:30:33 استخراج شده است.

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