PSYC 220 Week 6 Notes
PSYC 220 Week 6 Notes PSYC 220
Popular in Biopsychology
verified elite notetaker
Popular in Psychlogy
This 5 page Class Notes was uploaded by Lynde Wangler on Saturday February 20, 2016. The Class Notes belongs to PSYC 220 at University of North Carolina - Chapel Hill taught by Meghan Jones in Spring 2016. Since its upload, it has received 12 views. For similar materials see Biopsychology in Psychlogy at University of North Carolina - Chapel Hill.
Reviews for PSYC 220 Week 6 Notes
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 02/20/16
PSYC 220 Week 6 Notes Chapter 5-6 Vision and Other Sensory Systems Transduction – process through which nervous system converts light into electric signals Photoreceptors – rods and cones (depolarized in resting state and releasing glutamate); photopigments consist of retinal bound to opsins light stimulation will cause the retinal to let go of the opsin and release energy (bleaching); opsins modify which wavelengths each receptor is sensitive to Rhodopsin Activation – cGMP is the second messenger that is altered by the release of opsins; cGMP is abundant in the resting cell and keeps the Na+ channels open light activation causes enzymes to break down cGMP causing Na+ channels to close and the cell becomes hyperpolarized; this also decreases the release of Glutamate Response of Rods to Light: o 1) rhodopsin molecule is inactive o 2) Na+ channels kept open by cGMP o 3) Na+ ions flow into the rods partially depolarizing them o 4) rods continuously release glutamate Rods Response to Light: o 1) light bleaches rhodopsin molecules o 2) cGMP is broken down by enzymes and Na+ channels close o 3) Na+ ions cannot enter rods so rods become hyperpolarized o 4) glutamate release is blocked Transduction-Bipolar Cells: light always hyperpolarizes photoreceptors but photoreceptors can excite or inhibit neurons o ON center bipolar cells – glutamate inhibits this type of cell; photoreceptor stimulation excites this type of cell; less glutamate release = less inhibition so the cell is excited o OFF center bipolar cells – glutamate excites this type of cell; photoreceptor stimulation inhibits this type of cell; less glutamate release = less excitation so the cell is inhibited Transduction – Horizontal cells, Amacrine cells, and Ganglion cells: o Horizontal cells – receive information directly from photoreceptors and inhibit bipolar cells to further refine the information that is transmitted to the visual cortex o Amacrine cells – receive information from bipolar cells and synapse onto other bipolar cells (or ganglion cells); also to refine information in the visual system o Ganglion cells – glutamate always depolarizes ganglion cells; ganglion cells join to form the optic nerve where information is sent to the lateral geniculate nucleus (LGN) of the thalamus (though some projections extend to the superior colliculus and other areas) Lateral Inhibition – stimulation of a single cone receptor excites the bipolar and horizontal cells; the horizontal cell inhibits the surrounding bipolar cells (important for defining edges) Bipolar Receptive Fields – on-off center surround; distinct regions of excitation and inhibition; respond to specific orientations of bars of light Retinal Ganglion Cell Receptive Fields: o Parvocellular Small cell bodies, small receptive fields, mostly in or near fovea, responsible for detailed analyses of stationary objects, color- sensitive o Magnocellular Larger cell bodies, larger receptive fields, distributed evenly throughout the retine, respond to movement and broad outlines of shape, not color-sensitive o Koniocellular Small cell bodies, variable receptive fields, found throughout retina, color sensitivity and function varied Hierarchical Processing – sensory receptors, bipolar cells, ganglion cells, LGN cells, simple cortical cells, complex cortical cells Primary Visual Cortex – nasal visual field (closer to nose on each side) crosses over to opposite side of the brain while temporal retina (closer to lateral sides of head) remain ipsilateral; the LGN projects to the primary visual cortex (V1) aka striate cortex Blindsight is a condition in which some with damage to the V1 is still able to perceive the physical properties of light so when you throw a ball, they will move out of the way but not be able to tell why other than a random guess (but it must be more than this because they are able to do it a significant number of times) Simple Cells in the Visual Cortex: fixed excitatory/inhibitory zones (more light in the excitatory zone = more excitation, whereas more light in the inhibitory zone = less of a response); responds to particular orientation of bar or edge- shaped light stimuli; more likely to respond to vertical or horizontal orientation than diagonals Complex Cells in the Visual Cortex: located in V1 and V2; respond to a pattern of light in a particular orientation ANYWHERE within its large receptive field End-stopped Cells in the Visual Cortex: similar to complex cells but include a strong inhibitory areas at one end of the bar-shaped receptive field (if any light hits that inhibitory zone, the cell reduces its response); responds best to bars moving in a particular direction at a certain orientation; MOTION detectors Parallel Processing in the Visual Cortex: V1 projects to V2 V2 branches in several directions to parts of the parietal and temporal cortex ventral stream: WHAT pathway: through the temporal cortex / dorsal stream: WHERE/HOW pathway: through parietal cortex Inferior Temporal Cortex: cells in the inferior temporal cortex respond to our perception of objects, not the physical features of a visual stimulus o Visual Agnosia – the inability to correctly name an object even when features of that object can be detected perfectly fine (someone might say “round” and “red” and “curved” when describing something but not be able to identify it as an apple) o Feature detectors – a person with this condition can still identify features with accuracy and lucidity o Prosopagnosia – inability to recognize faces Specialization for Specific Visual Stimuli: o Parahippocampal (place area: PPA) cortex – images of places o Fusiform (face area: FFA) gyrus – faces (and emotionally relevant stimuli) o Adjacent to fusiform gyrus – bodies, biological motion o V4 – apparent or perceived color; color constancy Motion Perception: o Area MT (middle-temporal cortex) – aka V5; sensitive to particular speeds and direction of stimulus, acceleration and deceleration, etc.; photographs that IMPLY movement (running, jumping, driving, etc.) o Area MST (medial superior temporal cortex) – more complex stimuli; dorsal: expansion, contraction, and rotation; ventral: objects moving relative to their backgrounds Akinetopsia: motion blindness (trouble crossing street very common) damage to area MT; can see objects but not discern movement; MT also receives some input directly from LGN (damage to V1 produces blindness, but in some cases MT has enough info to sense motion) Development of the Visual System: o Most neurons within the visual system respond to corresponding areas in both eyes; retinal disparity – discrepancy between information from the left and right eye (necessary for depth perception); survival of appropriate synapses through the visual system is dependent on visual stimulation/input o Strabismus (“lazy eye”) – children attend to one eye or the other – treatment often includes wearing a patch over the unaffected eye to force them to attend to the affected eye Chapter 6 – Other Sensory Systems Sensory Transduction from a Broad Perspective: Generator potential – graded potentials that convert an environmental stimulus of any kind to an electrical change sensory receptor cell (the first EPSP/IPSP; graded potentials) Audition: sound waves are compressions or vibrations of air, water, or other media o Intensity (force per unit area, measured in decibels) or amplitude codes for loudness o Frequency (cycles per second, measured in Hz) codes for pitch Fundamental frequency Harmonics (multiples of fundamental frequency) Timbre (dependent upon waveform) Audition in Animals: o Humans – 20Hz to 20,000Hz (gradual decline with age) o Dogs – approximately 40Hz to 60,000Hz (dog whistles work for this reason) o Bats – approximately 20Hz to 120,000Hz echolocation o Mice – 1kHz to 90kHz (cannot hear the lower frequencies that humans can hear) Structures of the Ear: o Outer Ear – funnels sound waves to the middle ear; consists of pinnae (outer recognizable structure) o Middle Ear – amplifies signal “biological microphone” consists of tympanic membrane (ear drum), ossicles (hammer, anvil, and stirrup), oval window, *tensor tympani and stapedius – 200ms (these muscles contract to reduce sound within ear – this is why our voices do not sound ridiculously loud to us) o Inner Ear – consists of the cochlea, three parallel, fluid-filled canals scala vestibule, scala media, and scala tympani, as well as the organ of corti (contains the hair cells) Auditory Sensory Neurons have Preferred Frequencies: Outer hair cells have lower thresholds of excitation for some frequencies Pitch Perception: Place Theory: each area along the basilar membrane is tuned to a specific frequency of vibration; higher frequencies are coded for at the base of the basilar membrane while lower frequencies are at the apex this has to do with the shape of the membrane – the base is more narrow and stiff while the apex is wider and less rigid (imagine cords on a piano – the shorter ones are higher pitched whereas the longer ones are for lower pitches) Pitch Perception: Frequency Theory – basilar membrane vibrates in synchrony with the sound stimulation of auditory nerve causes action potentials to be phase-locked to the sound – A 100Hz sound wave would cause 100APs/sec Pitch Perception: Current Theory –> o Frequency Theory applies to low frequency sounds (<100Hz) o Volley Principle applies to higher frequency sounds (<4,000HZ) o Place Theory applies to super-high frequencies (>4.000Hz) Path of Auditory Impulses: o SONIC MG o Superior olivary nuclei (binaural input – some information crosses over at this point, inferior colliculi, medial geniculate nuclei Auditory Cortex: o Primary (A1) – tonotopic map o Anterior temporal cortex – “what” o Posterior temporal cortex – “where” o Superior temporal cortex – motion of sounds Secondary Auditory Cortex – changes in sounds, complex stimulus, sound meaning Sound Localization – intensity difference, time of arrival/latency difference, phase difference Hearing Loss: o Conductive deafness – ear fails to convert vibrations into waves of fluid (cochlea still functional) o Nerve deafness (sensorineural hearing loss) – hair cells fail to respond to vibrations o Tinnitus – constant ringing in the ears causes by damage to cochlea o Traditional hearing aid vs. Cochlear implants Vestibular System: consists of three semicircular canals, saccule and utricle, otoliths and hair cells; important for planning body movements and maintaining balance – where do you think information from the vestibulocochlear nerve goes? Motion Sickness: sensory conflict theory; caused by movements in the inner ear that we cannot control Somatosensation – sensory information travels up the dorsal column of the spinal cord and crosses over to the opposite half of the brain at the medulla oblongata Somatosensory Cortex – Dermatome: each spinal nerve innervates a limited area of the body – its receptive field; somatosensory thalamus innervates a specific part of the somatosensory cortex
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'