1 Perception the pathway for which information is 22 How we see PSB2000 Exam 2 round 2 carried 2 Ligand Stimuli effects are determined by receptors 3 The visual stimulus is light energy from a segment of the electromagnetic spectrum by transduced ultimately photoreceptors in the retina 4 Retina responsible for processing the refracted visual 6 Rods image through photoreptors 5 Photoreceptors line inside of retina send information Optic Nerve to the brain via shape movement lots of them light 7 Cones detect details they bright 1 of 3 colors work only in sensitive to light dark changes sensitive to 8 Ratio of Rods Cones 20 1 9 We see only the light rays that strike our retina in a chemicals Photopigments contain 10 Red Green cones are more numerous than Blue cones 11 3 2 Na in K out 12 Photoreceptors Tuned to upon contact w light perpendicular fashion energy that release specific wavelengths what we see is between 400 700 nm Young frequency in response to others compared to Thomas 13 How we see colors with only 3 receptors Trichomatic Young Helmholtz Theory 14 Perception of color of response in one cell frequency 15 Any move in wavelength spectrum will result in different colors 8 of 18 Photoreceptor Bleaching cones entering dark room 16 3 cones equally responding Grey 17 Colorblindness Color Vision Deficiancy exception males 0 5 of females is Blue Yellow colorblindness are working while rods not yet activated cones need lots of light while rods need upon entering but rods take time less to work to take over for cones rods are working but can t see colors well because they don t relay color information everything looks bright because exiting dark room rods become saturated and stop working in bright conditions cones take time to come back and take over cones activate and restore vision cortex compares information from various parts of retina to determine brightness color for each area perception of colors in 20 Opponent Process Theory increase in cells responding to terms of opposites dominant leads to opponent decrease image green color fatigued green cones so produce red weaker signals 19 Retinex Theory negative after 21 To the brain there is no difference between yellow light the overlapping red green light Photons of light are absorbed falls on Retina light hits Photoreceptors in the photoreceptors cis rhodopsin turn to trans when struck by light breakdown of Opsin causes Chemical Cascade that ultimately affect the conductance of Na channels and the conversion of the light stimulus to Electrochemical Signal signal is now sent to the brain 23 Without light Receptors inhibit bipolar cells 24 Bipolar cells are disinhibited can Cells by excitatory NT s stimulate Ganglion 25 Photoreceptors Horizontal Cells Bipolar Cells Amacrine Cells Ganglion Cells Optic Nerve Brain 26 Summary Light goes through a bunch of cells to the 27 Fovea NO RODS tightly packed Cones has acute Photoreceptors then back through the same cells to relay that signal to the brain detailed vision no nerves or Central Portion of the Retina this is the one ganglion one bipolar cell Blood vessels feeds to cell midget ganglion 70 of input with axon directly to brain direct route for registering location 28 Ganglion Cells in Forvea midget ganglion cell 29 Afferent Neuron 30 Information from both eyes meets at the Optic Chiasm 31 Most axons from the Ganglion cells go to the first order neurons Lateral accounts for 70 of input to brain Geniculate Ganglion Colliculus other areas deferred from firing an AP 32 Inhibition of the cells means that the cells are being Some go to the Superior 33 Occipital Cortex Thalumus talk constantly 34 Cells with similar properties are grouped together in columns perpendicular to the surface feature spatial 35 V1 Neurons can be described as frequency detectors sensitive to horizontal vertical pattern they can fatigue giving the opposite effect watching a waterfall for a while then looking at stationary objects immediately after they look like they re moving 36 Imagining actual seeing produce similar activity in V1 damage cause blind to actual imaginary images or dreaming images 37 Cells of Visual Cortex 1 Simple Cells V1 small ref field fixed excitatory inhibitory inputs that respond to location PSB2000 Exam 2 round 2 2 Complex Cells V1 V2 Med Ref field patter of light in particular orientation movement End Stop Hypercomplex Cells V1 V2 3 inhibitory area at one end of Ref Field stores 38 Cells that are resting are slightly depolarized no signals 39 Lateral Geniculate sends axons to Thalumus and Occipital being sent Cortex Striate Cortex 40 There are 5 areas for processing information 41 Primary Vision Cortext V1 42 Extrastriate areas V2 secondary vision cortex V5 has 2 streams of 43 V1 Striate Primary Cortex motion skilled coordination or actions Dorsal where how information hand eye location Ventral what pathway recognition of object and association with storage of long term memory inferior temporal cortex 44 Fusiform Gyrus responds strongly to faces right Agnosia inability to recognize causes 45 Damage to V1 despite normal vision 46 Cells respond to perception of objects rather than the hemisphere objects object itself 47 Prosopagnosia inability to recognize faces likely due to shortage of connections to fusiform 48 Posterior Parietal Cortex early integration with somatosensory proprioceptive vestibular signals discriminates painful stimulus nocefensive limb muscle movements cells in 49 Color Perception Afferent damage here perceived color of an object post parietal cortex can cause a loss of color constancy ability to recognize the true color of objects despite changes in light 50 Color Constancy are excited by V4 51 Middle Temporal Cortex MT aka V5 and Medial Superior Temporal Cortex MST receives input from LGN 52 In the MST Dorsal Cells converge their messages of objects or backgrounds moving onto Ventral Cells that respond to movement relative to background 53 Motion Blindness objects are visible but you don t see them moving visual areas in the brain decrease activity during voluntary eye movements saccades 54 Much of what we know comes from Cat Experiments 55 Experience has strong influences of development of 56 Stereoscopic Depth Perception our vision cortex responds to both eyes with corresponding inputs require retinal disparity 57 Retinal Disparity the discrepancy between the left right 58 Astigmatism blurring of vision for lines in one direction caused by asymmetric curvature
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