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Lecture 4

PSYCH 309 - Lecture 4 (Visual Representation) - Sept 17.docx

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PSYC 309
Todd Handy

September 17, 2013 Reading: Just Another Face in the Crowd, Indistinguishable Even if It’s Your Own • Heather Sellers: has prosopagnosia – face blindness o Sees faces that are human, all look more or less the same o Unable to even remember her own face in a photograph • Face blindness – rare result of stroke or brain injury o Consciously looks for details that others notice unconsciously o Develop alternate strategies for identifying people – clothes, mannerisms, hair, voice o Sometimes accompanied by other problems – directions, distinguishing cars, etc • 2.47% of 689 randomly selected students in Germany • No known cure, some people don’t know they have it • Can typically understand facially expressed emotions, facial cues, determine gender o See face clearly, but cannot remember once they stop looking • MRI brain scans – real time imaging showing active parts of the brain • Fusiform gyrus – responds more strongly to faces than other objects, identity- related processing • Researchers – prosopagnosics: don’t see different response in brain when looking at 2 faces • Evidence that trait is inherited, though haven’t found specific gene for disorder When family looks strange and strangers look normal: A case of impaired face  perception and recognition after stroke • 62 year old female patient – ischemic stroke o Impaired recognition of basic emotional expressions o Poor recognition of familiar faces o Faces of family members distorted • Assessed explicit recognition as well as autonomic responses to photographs by measuring skin conductance responses o Lower overall psychological arousal to the stimuli • MRI showed a lesion in occipitotemporal area, mostly affecting middle temporal gyrus of right hemisphere • Recognized daughter who she had not seen in 8 years, didn’t recognize closer daughter • Tests – mild integrative agnosia: inability to integrate single components of an object into a holistic percept o Impaired perception of facial expressions of emotions o No apparent problem with spatial processing and object perception • Identified celebrities (mistaken look-alikes), not family members (looked strange/repulsive facial proportions distorted) o Slower and less accurate at recognizing pictures • Capgras delusion – belief that close acquaintances (parents, children) have been replaced by impostors, robots, aliens • Prosopometamorphopsia – perceptual distortions of whole or only half or part of face • Distorted face perception and impaired face recognition = emotional relevance of faces • Posterior superior temporal sulcus (pSTS) – emotional expression, eye gaze, mouth movements Dual Visual Pathways • How pathway –> Motor strip o Just do it, don’t have to think about it, effortlessly o We are implicitly aware of what is going on o Eye  Hand knows where to go unconsciously • What pathway o Used for how we process faces • Pareidolia – seeing things (e.g. faces) in otherwise “random” objects/stimuli o What do we pick up from seeing faces? – emotional, etc o Reflects hard wire circuitry that is designed to see faces in things that don’t exist The Visual Agnosias (Fusiform Gyrus) • Apperceptive agnosia – Pink – don’t perceive, not blind, but it’s jumbled o Earliest part of the “what pathway” o There’s no real object perception • Associative agnosia – green – not quite as bad, what pathway starts assembling visual images, o You can pick up on basic shapes and sizes, but hard time putting parts and pieces together, can’t organize it into a whole • Prosopagnosia – deficit to perceiving faces, but can recognize other objects , on right side only o Split brain – e.g. paintings presented to left = face, to right facial field = vegetables Iclicker: • What do we learn from NYT “face blindness” article? o Prosopagnosia can be congenital [born with it] or acquired due to brain damage o People can be recogni
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