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PSYC2390 CH Notes (Post midterm 1/ for midterm 2).docx

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PSYC 2390
Lana Trick

PSYC2390 CH Notes Part 2 CH 1 contd 34 Receptive fieldof a neuron area on receptors that influences firing rate of neuron o ie visual receptors line back of eye in retina and optic nerve transmits signals out of eye o indicates location and sizeshapethat causes best responseExcitatory areaof neurons receptive field stimulation causes increase in neurons firing rate Inhibitory areastimulation causes decrease in firing rateCentersurround receptive fieldareas of the receptive field are arranged in a center region that responds 1 way and a surround region that responds in the oppositeo excitatorycenterinhibitorysurround receptive field or inhibitorycenterexcitatorysurround receptive field o also occur in skinCentersurround antagonismeffect of center and surround of receptive field responding in opposite ways o ie small spot presented to excitatory center of receptive fieldsmall increase in rate of nerve firing increasing lights size to cover entire centre of receptive field increases cells responsecentersurround antagonismspot of light large enough to cover inhibitory area stimulation counteracts centers excitatory responsedecrease in firing rateneuron respondsbest to spot of light size of excitatory center of receptive fieldelectrical impulsesperceptionsSpecificity codingrepresentation of particular objects in environment by firing of neurons tuned to respond specifically to that object ie faces Grandmother cellneuron that responds only to a specific stimulus ie specific image o respond to different views of a stimulus modes of depiction and words signifying the stimulus respond to visual featuresand representative concepts o in the hippocampus and MTL associated with storage of memories wellremembered objects represented by firing of few specialized neuronsDistributed codingneurons respond toof different stimuli a particular object is represented by the pattern of firing of groups of neurons not single neuronSparse codingparticular object represented by firing of a relatively smallof neuronso between specificity and distributed o ie code for representing objects in visual system tones in auditory system and odours in olfactory system Mindbody problemhow physical processes ie nerve impulses or sodium and potassium molecules flowing across membranes body become transformed into perceptual experience mindNeural correlate of consciousness NCCresearch on connections between stimuli in environment and firing of neurons consciousness roughly defined as experiencesEasy problem of consciousnesspossible to discover many connections between neural firing and experienceo problem how physiological responses cause become transformed into experienceHard problem of consciousnesshow sodium and potassium ions flowing across the membrane or nerve impulses result in perception CH 3 contd 61 Lateral inhibitiontransmitted across the retina o ie examine horseshoe crab limulus eye made up of 100s of ommatidiaeach has small lens on eyessurface located directly overa single receptorillumination of receptorlarge response illumination to nearby receptorsdecreased responsey by lateral inhibition transmitted across eye by fibers of lateral plexus transmits signals laterally y horizontal and amacrine cells transmit signals across human retina Lightnessperception of shades ranging from white to grey to black Hermann gridgrey ghost images at intersections of white area decreases or vanish when look directly at intersection lateral inhibition o bipolar celllightness of receptor determined by response of its bipolar cell response depends on amount of stimulation received from receptor and on amount of decrease in response by lateral inhibition received by neighbouring cellsthy lateral inhibition sent by each receptors bipolar cell110 of each receptors responsey response of a receptors bipolar cellinitial responseof a receptors bipolar cellinhibition sent from the other bipolar cells Mach bandsillusory light and dark bands near a lightdark border o initial response received by each bipolar cellamount of inhibition that each bipolar cell threceives from neighbours assume 110 of cellsinitial outputfinal response of each cellreceptors send signals to bipolar cells each bipolar cell sends lateral inhibition to its neighbours on both sides Simultaneous contrastour perception of brightness or colour of 1 area is affected by presence of an adjacent or surrounding area ie same colour squares on light and dark background appear different oreceptors under the 2 small squares receive same illuminationreceptors under light area surrounding the small square on the lighter square are intensely stimulated send large amount of inhibition to receptorsy response decreased more fire less small square looks darkerreceptors under dark area surrounding the small square on the dark square are less intensely stimulated send less inhibition to receptors Whites illusion2 vertical rectangles in horizontal lines 1 looks much darker but both reflect same amount of light cannot be explained by lateral inhibition Belongingnessan areas appearance is influenced by part of surroundings to which the area appears to belong light surroundingdarker inner appearance vice versa more lateral inhibitionmore border surrounded by whiteinner looks darker perceptionindirect processillusion o ie see cup because light is reflected from it focused onto the retina changed into electricity and processed by mechanisms ie convergence excitation and inhibition perception of heat and texturestimulation of temperature and pressuresensitive receptors in fingers translated into electrical impulsessmell and tastestimulation of receptor sites causes electrical signals processed by nervous system to create experience hearingair causes vibrations of receptors in ear electrical signalssoundCH 4light reflected from object into eye light focused to form image of object on retina o light illuminates some receptors intensely and some dimly absorbed by visual pigment molecules that pack the rod and cone outer segmentso chemical reactions in outer segments transducer light into electrical signals travel through retina interact excite and inhibit
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