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PSYC 1000
Benjamin Giguere

VISION AND PERCEPTUAL ORGANIZATION AND INTERPRETATION Vision  Our eyes receive light energy and transduce (transform) it into neural messages our brain then processes into what we consciously see. The stimulus input: Light Energy  What we see as a visible light is but a thin slice of whole spectrum of electromagnetic energy ranging from imperceptibly short gamma waves to the long waves of radio transmission  2 physical characteristics of light help determine our sensory experience of them  Light’s wavelength the distance from one wave peak to the next determine it hue (colour we experience)  Intensity the amount of energy in light waves (determined by a wave’s amplitude, or height) influences brightness The physical properties of waves Waves vary in wavelength. Frequency, the number of Waves vary in amplitutude. Wave amplitutde Complete wavelengths that can pass a point in a given determines the intensity of colours. Time, depends on the wavelength. The shorter the Wavelength the higher the frequency. The Eye  Light enters the eye through the cornea, which protects the eye and bends light to provide focus  The light then passes through the pupil, a small adjustable opening  Surrounding the pupil and controlling its size is the iris, a coloured muscle that dilates or constricts in response to light intensity and even to inner emotions  Behind pupil is a lens that focuses incoming light rays into an image on the retina, a multilayered tissue on the eyeball’s sensitive inner surface  The lens focuses the rays by changing its curvature in a process called accommodation  Retina receives upside-down image  The retina does not see the whole image but instead its millions of receptor cells convert particles of light energy into neural impulses and forward them to the brain. There, the impulses are reassembled into a perceived, upright image VISION AND PERCEPTUAL ORGANIZATION AND INTERPRETATION The eye Light rays reflected from a candle pass through the cornea, pupil, and lens. The curvature and thickness of the lens change to bring nearby or distant objects into focus on the retina. Rays from the top of the candle strike the bottom of the retina, and those from the left side of the candle strike the right side of the retina. The candle’s image on the retina thus appears upside-down and reversed. The retina  Rods retinal receptors that detect black, white and grey; necessary for peripheral and twilight vision when cones don’t respond  Cones retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. The cones detect fine detail and give rise to colour sensations  There you would see the light energy trigger chemical changes that would spark neural signals, activating nearby bipolar cells.  The bipolar cells in turn would activate the neighbouring ganglion cells, whose axons twine together like the strands of a rope to form to optic nerve that nerve carries the information to your brain, where your thalamus stands ready to distribute the information  Where the optic nerve leaves the eye, there are no receptor cells- creating a blind spot  Cones cluster in and around the fovea the retina’s area of central focus  Each one transmits to a single bipolar cell that helps relay the cone’s individual message to the visual cortex, which devotes a large area to input the fovea  These direct connections preserve the cones’ precise information, making them better able to detect fine detail  Rods share bipolar cells with other rods, sending combined messages  Your eyes adapt in the dark your pupils dilate to allow more light to reach your retina VISION AND PERCEPTUAL ORGANIZATION AND INTERPRETATION The retina’s reaction to light Visual Information Processing  Visual information percolates through progressively more abstract levels on its path through the thalamus and on to the visual cortex  Information processing begins in the retina’s neural layers, which are brain tissue that migrated to the eye during fetal development  These layers pass electrical impulses, and help to encode and analyze sensory information  After processing by your retina’s rods and cones, information travels to your bipolar cells, then to our ganglion cells, and through their axons making up the optic nerve to your brain  Any given retinal area relays its information to a corresponding location in the visual cortex, in the occipital lobe at the back of your brain  The same sensitivity that enables retinal cells to fire messages can lead them to misfire Pathway from the eyes to the visual cortex Ganglion axons forming the optic nerve run to the thalamus, where they synapse with neurons that run to the visual cortex VISION AND PERCEPTUAL ORGANIZATION AND INTERPRETATION Feature Detection  Feature detection specialized neurons in the occipital lobe’s visual cortex receive information from individual ganglion cells in the retina  Ability to respond to a scene’s specific features (movements, lines)  These cells pass this information to other cortical areas, where teams of cells (super cell clusters) respond to more complex patterns  One temporal lobe area by right ear enables you to perceive faces and thanks to a specialized neural network, to recognize them from varied viewpoints Parallel Processing  To analyze a visual scene, the brain divides it into sub dimensions-colour, motion, form, depth-and works on each aspect simultaneously  We then construct our perceptions by integrating the separate but parallel work of these different visual teams  to recognize a face, your brain integrates information projected by your retinas to several visual cortex areas, compares it to shored information, and enables you to recognize the face  separate visual systems for perception and action illustrate dual processing Summary of visual information processing VISION AND PERCEPTUAL ORGANIZATION AND INTERPRETATION feature detection: brespond to specificls features- edges, lines and angles retinal processing: parallel processing: brain receptor rodes and cones - cell teams process > bipolar cells -> gangilion combined information cells about colour, movement, form, and depth reocognition: brain interperts the constructed scene images based on information from stored images What is the rapid sequence of events that occurs when you see and recognize a friend? Light waves reflect off the person and travel into your eye, where the receptor cells in your retina convert the light waves- energy into neural impulses sent to your brain. Your brain processes the sub dimensions of this visual input- including colour, depth, movement, and form- separately but simultaneously. It interprets this information based on previously stored information and your expectations into a conscious perception of your friend Colour Vision  colour like all aspect of vision, resides not in the object but in the theater of our brains, as evidenced by our dreaming in colour  colour is mental construction  Young-Helmholtz trichromatic (3 colour) theory the theory that the retina contains 3 different colour receptors- one most sensitive
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