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48 Cards in this Set
- Front
- Back
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What is the general organization of sensory systems like?
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A hierarchical system of plates - cells that process information as it moves thrugh the nervous system.
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What is the definition of a receptive field?
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A region within which an individual neuron's activity may be influenced.
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3 examples of receptive fields:
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-area of the retina
-area of skin -area of the basilar membrane |
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What type of influences can be stimulated by the receptive field?
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Excitory, inhibitory, or both.
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Topography means:
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Configuration of a surface in a way that it maps the organ from which it receives input.
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3 types of topography:
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-Retinotopy
-Somatotopy -Tonotopy |
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What is retinotopy?
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A map of the retina
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What is somatotopy?
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The map of the homunculis
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What is tonotopy?
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The map of the basilar membrane.
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Why do topographical maps look distorted compared to the actual map of a sensory organ?
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Because of areas that have high receptor densities, but little spatial summation. They require more cortex for integration.
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Why is it hard to pinpoint where someone touches you on the back compared to your hands?
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-Lots of spatial summation in back; touch receptors converge to go to brain in one fiber
-Less in hands - individual fibers for each receptor. |
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So in general the sensory system layout is:
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Predictable - by Topographical maps.
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How is it possible that Topographical maps can be made?
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Because axons in the cortex tend to remain adjacent as they pass through the nervous system to innervate adjacent receptors.
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How does development affect topographical organization in sensory systems?
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There are active mechanisms that refine it during development.
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What happens to sensory information as it progresses through hierarchical plates?
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It is processed.
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What type of connections are found in the sensory systems?
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-Straight through
-Lateral inhibitory |
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What type of connection are straight through connections?
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Almost Always Excitatory
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What is the function of lateral inhibition?
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To sift out unimportant information and extract important information.
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2 types of sensory neuron responses:
What is predominant? |
1. Graded potentials (most)
2. Action potentials |
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Function of graded potentials:
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To process info in an analog way.
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Function of Action potentials:
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To send info over long distances.
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How many neural types in the retina?
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5
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How many produce action potentials?
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1 type
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What is the deal with the thalamus?
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All sensory information passes through them on their way to the cortex except some olfactory info.
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How are the thalamic nuclei arranged?
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Each sensory system has its OWN set of relay nuclei.
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What do Labeled Line codes in neurons give information about?
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QUALITY of a stimulus - modality
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What is modality?
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The quality of stimulus
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What increases the specificity of information encoded in a labeled line?
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The degree of TUNING
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What information do Frequency codes give?
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Intensity
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2 other types of codes:
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-Temporal
-Population |
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What are population codes?
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Pattern codes that disambiguate the modality and intensity of broadly tuned receptors.
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What are temporal codes?
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Like Morse code?
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What are sensory signals designed to signal?
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Change
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What is receptor adaptation?
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A decrease in the initial vigorous response to a stimulus if the stimulus stays on for a long time.
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2 ways that sensory systems are designed to signal change:
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1. Receptor adaptation
2. Lateral inhibition |
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What is lateral inhibition?
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Silencing of neural activity via interneurons between adjacent cells.
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What is the purpose of lateral inhibition?
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To enhance the difference between two adjacent objects. (ie vision of light/speck)
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What is the prominent exception to sensory systems being designed to signal change?
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Pain - it can be constant as we all know.
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What are Psychophysical methods for?
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Measuring our sensory INABILITIES.
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What is the definition of psychophysical?
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A psychological reaction to a physical stimulus. (you get touched and then tell about your feelings)
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What is "Threshold"?
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The point of intensity at which a stimulus can just be detected.
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What is Absolute Threshold?
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How MUCH intensity must be impinged to just be detected.
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What is Difference Threshold?
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The magnitude of difference between the intensities of two stimuli that can be differentiated by the person.
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What does Weber's law tell us?
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How sensitive a sensory system is in relation to the Stimulus Intensity
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What is the equation for Weber's Law?
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deltaI/I = k
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What is delta I?
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The intensity of a stimulus increment that can just be barely detected when added to an already present stimulus.
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What is I?
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The intensity of background stimulus
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what is k?
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A constant
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