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Chapter 4

Lecture 9,10 + Textbook Chapter 4.pdf

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University of British Columbia
PSYC 101
Michael Souza

Lecture 9 principles of sensory processing ocular anatomy and basic visual processingTextbook Chapter 4 In generalSensaon o Transducon bringing info from enviromaking it a neural signal o Receptor cells pick up info tailored to specic sensePercepon making sense of signals process of recognizing interpreting neural signals and appreciang variability o Anatomical coding diff features are coded by the acvityof di neurons interprets locaontype di features are coded by acvity of di neurons o Temporal coding diff features are coded by the paern ofacvity of neurons int intensity using me o Height of action potenal is always the same so the dinumber of AP is based on intensity more sensingmore acon potenals Transducon informaon has been taken fromone form into a meaningful neural signal VisionOpc chiasm in the middleLe opc eld and right opc eld cross in the middleLight energy Length colour amplitudeheight brightness purity saturation is it one colour or a combo of colour Wavelengths shortestpurple blue longestredOur eyes are tuned to pick upa parcular secon of the electromagnec spectrum Eye anatomyPupil opening in the eye light photons enter here size is controlled by the iris when its bright it gets smallerdilangdues can change sizes depending on the environment light informaon etc contracts or relaxes depending on the amount of light or informaonIris coloured part of the eye controls the size of the pupil Lens disk that helps send image to back of eye through refraction inverts the imagewhen informaon hits the lens it is sent to the back of the eye but backwards image in the back of the eye is upside downxed by our brainRena capture crisp and visual informaonFovea contains receptors lets you see HD good detail concentrang aka foveatingseeing clearer Blindspot where opc nerve leaves the eye no photoreceptors there o What1doesntseetheother will llinthegaps o If you cover one eye the brain will ll in the blind spot educated guess o Movement also helps ll the gap o with help from the brain and both eyes the information can be filled inLight reflected from a surface enters the eyes via the transparent cornea bending to pass thru the pupilthe centre of the coloured iris muscles to move eye behind the iris the thicknessshape of the lens adjust to focus light on the retina where the image appears upside down and backward Vision is clearest at the fovea Lightsensitive receptor cells in the retinal surface excited or inhibited by spots of lights influence the specialized neurons that signal the brains visual centers through their bundled axons which make up the optic nerve optic nerve bring info to the brain optic nerve creates the blind spot blind spot from left eye is filled in by the right eye The dysfunconal eyeNearsightedness eye is too long requires concave lensFarsightedness eye is too short requires convex lensCataracts blurry lens so image sent is also blurry aging eye turns yellow Glaucoma too much pressure in the eye uid gets trapped and puts pressure on the opc nerve maybe from uid blockagebuild up tested by shining light in eye and pu air in it loss of periphery dark around the image Macular degeneration retina degenerates mac lines up w fovea so central focus is destroyed hallucinaons occur if brain tries to ll in the blind spot macula foveaback of eye degenerates periphery is ne but focus starts to swirl loss of central vision macula is part of the renaRetina tear uid gets thinner and sneaks under retina tearing it o ageing and you lose vision where its torn can also occur due to trauma Papilledema brain swells and pushes the opc nerve out must immediately releaserelieve pressure observable Colour blindness cone based blindness common redgreen blindness 111 of men sex linked gene dysfuncon level of the eye The fovea focusing processing informaon more detailed than otherwise possible have photoreceptorsRods for blackwhite vision seeing in the darkperiphery 120 million photoreceptors awayfrom the fovea detecng moon dim lighng condions located away from the fovea periphery of rena most on sideCones for colour visionfine resoluon 7million centered in the fovea Photoreceptors near capillary beds for access to energynutrients back of rena being cells 1cell 10conesGroup of ganglion cells forms the receptive field of a cell in the brain On center cell is smulated when centre of eld is exposed to light and inhibited when the surround is exposed to light opp of o center gangNumerous overlapping recepve elds help map precise info they are more rods than conestheyre translucent do not aect vision light not blocked theyre in front of the fovea Transducon1 Light enters the eye through the lens2 Image on lens is refracted back to the retina image inverted3 Reaches back of eye activates rodscones 4 Bipolar ganglion cells summarize info info as few neurons as possible head to exit the eye forward5Infoleavesviablindspotfor further processing renal ganglion cellbipolar cell summarizing and bringing together the informaondi neurons corresponds for di parts of the space which part of the
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