Biopsychology Week 4
Biopsychology Week 4
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This 3 page Reader was uploaded by Monica Stert on Friday April 25, 2014. The Reader belongs to a course at University of California Santa Barbara taught by a professor in Fall. Since its upload, it has received 80 views.
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Date Created: 04/25/14
V Vision A The Visual System 1 Light a Quanta electromagnetic radiation that comes in very small packets b Wavelength each quantum can be described by the distance between to adjacent crests of vibratory activity c Photons we only respond to a narrow section of the electromagnetic spectrum d Long wavelength and slow frequency perception of red short wavelength and fast frequency perception of blue 2 Human Eye a Iris color contractile tissue b Pupil hole formed by iris to admit light 1 An iris dilates when there is a lack of light it contracts when there s a lot of light high acuity detailed vision sensitivity is important c Cornea outer layer transparent and first refraction of light d Lens transparent behind iris that focuses light e Ciliary muscle controls shape of or accommodates lens object close lens rounds object far lens flattens f Binocular disparity the slight difference between the views from the two eyes important for depth perception g Fovea small area at the center of the retina that has a dense concentration of cones and maximal visual acuity h Optic nerve ganglion cell axons that extend from retina to optic chiasm i Optic disc contains no photo receptors blind spot in visual system 3 Retina a Layer of neurons 1 Receptor cells light first hits system 2 Bipolar cells take info and send 3 Horizontal cells lateral communication 4 Amacrine horizontal between bipolar and ganglion 5 Ganglion cells axons from optic nerve b Photoreceptors and tradeoffs 1 Photopic system cones pigment 3 opsins for red blue and green low sensitivity fovea rapid temporal response high acuity 1 to 1 convergence 2 Scotopic system rods pigment Rhodopsin high sensitivity outside fovea low acuity slowlong latency high convergence which makes rods sensitive B Visual Transduction 1 Rod photoreceptor that receives light as input instead of neurotransmission a Rhodopsin photopigment within outer segment sensitive to light b In darkness a rod continuously fires a potential releases glutamate c When light hits rhodopsin light photon breaks down G protein that leads to shutting down of sodium channels hyperpolarizes receptor and blocks it from releasing glutamate d The potentials photoreceptors send are graded e When photoreceptor sends signals 1 Oncenter bipolar cell communicates with oncenter ganglion increases firing rate via depolarization 2 Offcenter communicates with offcenter ganglion hyperpolarizes decreases firing rates 3 2 signals sent to brain light is on and light is not off 4 Turn light off opposite effect C Major characteristics of system 1 Its sensitivity because weak stimuli are amplified to produce physiological e ect 2 Its integration of the stimulus over time which makes vision slow but highly sensitive 3 Adaptation to wide sensitivities D Pathways 1 Light is sent along axon in optic nerve to thalamus makes first synapse at lateral geniculate nucleus hits in occipital lobe 2 Vision is well lateralized left side of eyeball to left right side of eyeball to right 3 Maintains spatial relations called retinotopic organization 4 M and P channels of lateral geniculate nucleus a Parvocellular layers layers 36 small cell bodies sensitive to color and fine details b Magnocellular layers layers 12 large sensitive to motion 5 Adaptations a Lateral inhibition color bars interconnected neurons inhibit their neighbors enhancing the contrast at the edges of a region black dots seen with white grid E Receptive fields action potentials of neurons selectively respond to certain kinds of light within a small area of the visual field Hubel and Wiesel 1 On centeroff surround cells centric receptive fields in which stimuli in the center excites the cell of interest while stimuli in the surround inhibits the cell 2 Neurons are sensitive to orientation of light as well true of neurons in thalamus a Areas of cortex are selective on which way the object moves 3 Visual cortex is organized in columns cortical regions driven by stimuli in four different orientations are each coded in color a Color vision 1 Component theory trichrome ability to see spectrum depends on red blue and green cones 2 Opponent process theory color vision depends on systems that produce opposite responses to light of different wavelengths yellow blue blackwhite redgreen and color after effects VI Visual Perception and Attention A Visual Areas 1 Organized into different regions and layers that specialize a Primary visual b Secondary visual receives direct projections from the primary cortex c Visual association cortex from secondary cortex 1 Scotoma damage to primary visual cortex leads to blindness in one half of brain or other visual field in half 2 Blindsight ability of patients to respond to stimuli in their scotomas even though they have no conscious awareness of the stimuli islands of spared tissue 2 Hierarchial organization leads to cells and groups that are sensitive to particular objects grandmother cells 3 Streams a Dorsal information flows from primary to parietal cortex specializes in visual spatial perception what vs where theory b Ventral primary to interotemporal visual pattern recognition 1 Visual agnosia failure to visually recognize objects can t put it together into a recognizable object not memory or vision problem 2 Fusiform face area FFA inferior temporal lobe fusiform gyrus specialized for face recognition a Prosopagnosia damage to FFA visual agnosia for faces only she can point out facial features but can t organizerecognize ventral c Selective attention 1 Hemispatial neglect neglect syndrome damage to the posterior parietal cortex can lead to deficit in attention to the opposite contralateral side of spaceattending to things in that space can often get better after a few years 2 Change blindness happens because we re not taking in everything at once blank screen for 80 ms that attention system has to overcome shows visual attention is quite limited
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