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PSYCH 261 (91)


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Deltcho Valtchanov

Vision Chapter 6 The Stimulus *Sensory Receptors *Neurons that detect a particular category of physical events. *Sensory Transduction *Process by which sensory stimuli are transduced into slow, graded receptor potentials. *Receptor Potential *Slow, graded electrical potential produced by receptors in response to physical stimuli. *Actual electronic potential that happens in Sensory transduction The Stimulus *Perceptual dimensions of colour *Hue – the dominant wavelength; the color of the light that’s coming into the eye *Shorter wavelengths – bluish – violet colors *Longer ones – reddish color *Perceptual dimensions of colour *Brightness – intensity; increase in brightness, increase in intensity *Saturation – purity; increase in saturation, increase in wavelengths The Eyes *Eye movements *Vergence – cooperative eye movements, ensures the image falls on identical portions of each retina. *Convergence (looking towards the same point) vs. Divergence (looking into different directions) *Saccades – rapid, ballistic eye movements (video, moving back and forth eye) *Overt attention – bring power of fovea to bear on objects *Smooth Pursuit – eye movements tracking a moving object. The Eyes *Oculomotor muscles *Three of twelve cranial nerves dedicated to controlling eye movements (oculomotor, trochlear, abducens) Vestibular-ocular Reflex Eye movements that compensate for head movements Nystagmus – alternating smooth pursuit in one direction followed by saccades in the opposite direction *Anatomy of the Eye *Lens *Ciliary Muscles – control the shape of the lens. **They didn’t work for older peoplehyperopia *Accommodation – changes in thickness of the lens, accomplished by the ciliary muscles, focuses images of near or distant objects on the retina. The Eye *Retina *Photoreceptors – transduces photic energy into electrical potentials. *Rods – sensitive to light of low intensity; sensitive to light, changes in contrast, movement and motion; used for night visions *Cones – maximally sensitive distinct wavelengths; encodes color. *receptors sensitive to color; very sensitive to different wavelengths or light; where your details come from *Fovea – region of the retina that processes central 4 to 6° of vision.; *Cones the only photoreceptor found in the fovea *Bipolar Cells – middle layer of retina, conveying information from photoreceptors to ganglion cells. *Blue one – horizontal cell – connects adjacent rods and cones; connects them and aggravates and make them function as one giant receptor *Ganglion Cells – conveys information from bipolar cells to brain via the optic nerve. *Not important: Horizontal Cells – interconnects adjacent photoreceptors and the outer processes of bipolar cells; connects the rods and cones and connects them all and makes one big receptor *Amacrine Cells – interconnects adjacent ganglion cells and the inner processes of bipolar cells. The Eye *Optic disc and the blind spot – where your optic nerve *The brain fills in the missing info in the blind spot *We’re not aware of our blind spots *Photoreceptors *Lamellae – layers containing photopigments. *Photopigment – protein dye bonded to retinal (a lipid) responsible for transduction of visual information. *Opsin – class of protein that act as a photopigment. *Retinal – chemical synthesized from vitamin A that acts as a photopigment The Eye Change Blindness We do not have a full and complete representation of everything we see! Change blindness- you’re not aware of the things that you’re not paying attention to From Eye to Brain *Dorsal Lateral Geniculate Nucleus (LGN)
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