Lecture 9 Notes F09

Lecture 9 Notes F09 - PSYCH 301 LECTURE 9 Sensory Systems...

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PSYCH 301 LECTURE 9 Sensory Systems: Vision Part I: The Retina I. Principles of Perception:  The brain must receive information about the  outside world and execute behavior through systems outside the CNS. A. Firstly,   perception   must   be   differentiated   from   sensation.  Sensation   is a passive process which simply means the detection of  certain   types   of   stimuli   (i.e.   light,   sound,   heat,   a   chemical,   etc.).  Perception  is an active process which involves not only the integration of  basic sensory inputs, but also the selection of inputs and active inhibition  of some input. B. Types of sensory input 1. Chemical :  smell and taste, but also CO 2 , pH and osmotic  pressure. 2. Mechanical :   Touch, hearing, vestibular, joint position and  movement, muscle tension 3. Photic :  Sight 4. Thermal :  Warmth, cold 5. Some   other   species   have   other   sensations,   for   instance  perception of electrical fields. C. Basic concepts 1. Threshold   stimulus :     Sensory   systems   have   a   certain  threshold of stimulation level for detection (similarly they also have a  maximal level).
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2. Range of responsiveness :   light actually differs in three  qualities   -   hue   (wavelength),   brightness   (intensity)   and   saturation  (purity).  The maximum and minimum observable hue defines a range of  responsiveness,   which   differs   by   species;   for   humans   the   “visible”  spectrum is from about 400 to 700 nm.   3. Receptors :     The   detection   of   particular   kinds   of   inputs  requires particular receptors, often termed   traducers .   This defines the  input   as   being   of   a   particular   type   as   it   passes   upward   through   the  nervous system. 4. Intensity :  In addition to quality of the stimulus the quantity  is also transmitted. 5. Adaptation :     Sensory   receptors   are   of   two   types,   tonic  receptors ,   which   do   not   habituate   to   constant   input,   and   phasic  receptors  which habituate to constant input. 6. Lateral Inhibition :   When a stimulus impinges on a large  number of receptors, it is perceived most sharply at the edges of the  receptive field.  This sharpening is achieved through lateral inhibition:  the  last   neuron   within   the   field   receives   the   least   inhibition   from   other  stimulated neurons, while the first neuron outside the stimulated field is  inhibited by neurons within the field, unlike its neighbors farther away from  the stimulation field. III.
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This note was uploaded on 02/26/2011 for the course PSYC 301 taught by Professor Yager during the Spring '10 term at Maryland.

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Lecture 9 Notes F09 - PSYCH 301 LECTURE 9 Sensory Systems...

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