4_pathways - Pathways -> (LGN) Parallel Processing...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Pathways -> (LGN) Parallel Processing Streams Magnocellular "where" vision motion, contrast, depth parietal lobe spatial orientation Parvocellular "what" vision form, color, depth temporal lobe object recognition Lateral Geniculate Nucleus (LGN) Lateral Geniculate Nucleus (LGN) 6 layers each layer from 1 eye 4 layers from parvocellular 2 layers from magnocellular 1 Hubel & Wiesel (1962) - orientation - ocular dominance - retinal position Seeing the World in 3D "Cues" to the lost third dimension Monocular/Pictorial Cues that are available in the 2D image Occlusion 2 Height in the Field of View Atmospheric Perspective Linear Perspective Linear Perspective & Texture Size and Distance Emmert's Law S p = C(S r x P p) where Sp = perceived size Sr = retinal size Pp = perceived distance 3 Ames Room Shading and more... Seeing Depth The Cue Approach Binocular stereopsis disparity oculomotor cues Muscle proprioception 4 Disparity = q 1-q 2 Perceiving Objects and Forms q1 q2 Task Surface perception a complete 3D representation or map of scene - motion, stereo etc. segment into "figure" and "ground" Performance Factors knowledge and experience principles of perceptual organization attention expectations Segment/parse into objects Which points in map belong to same objects? Recognize and identify objects represent, remember and match to memory Scene perception layout of objects Events meaningful sequences of scenes 5 Object and Shape Recognition Direct analysis of shapes Problems Viewing angle Photometric problems - illumination, viewpoint, shadows, highlights Object setting - isolation, occlusion Rigid, non-rigid - animated Object and Shape Recognition Theories Structural theories (3D) Find parts Identify parts Describe structural relations among the parts Shape invariants Properties of shape common to all views Feature list that specifies object Good - some success in limited situations Bad - not generally applicable Object and Shape Recognition Theories Recognition by components (Biederman, 86) Geons (about 50) least changeable with viewpoint maximize image features that generalize psychological evidence Object and Shape Recognition Theories (continued) Image-based models Interpolation models (Poggio & Edelman, 91) 2D image analysis Store multiple views Interpolate in image space Special or canonical views Alignment models (Ullman 90's) Within a category - solve correspondence Align to a "special" view Transform from 2D to 3D Match Auditory System What is a sound? (def) - pressure variation in t around the mean atmospheric pressure How do you make a sound? vibrations resonance 6 Dimensions of Sound frequency number of sounds waves to pass any point in a second measure - cycles per second or Hertz psychological correlate - pitch amplitude magnitude of the movements produces timbre whatever is left after equating pitch & loudness measure - pressure in decibels psychological correlate - loudness psychological correlate - sound quality Complex sounds frequency composition amplitude associated with each frequency complex recipe reflected and absorbed sounds...like vision 7 Kinds of representations Easiest x axis - time y axis - sound pressure level Fourier spectrum x axis - frequency y axis amplitude spectrogram y axis - frequency x axis - time intensity of markings - amplitude Function of Auditory System communication and language identification of prey/predator sound localization balance - structure and function of system? outer middle Structure of the Ear middle ear bones inner cochlea semi-circular canals 8 Function of the outer ear - filtering of the sounds - define best frequencies - analogy to vision - best hues Tympanic membrane - ear drum at border between outer and middle Middle Ear Parts- 3 tiniest bones in the body malleus incus stapes Function impedence mismatch 9 Middle ear reflex - triggers - to loud sounds > 75dB - to vocalization - tactile stimulation of head, body - benefit -ear protection (stimulation deafness) Inner Ear cochlea semicircular canals COCHLEA UNROLLED Basilar Membrane pliable Helicotrema 3 canals 2 membranes - basilar - Reissener's Oval window stiff 10 Organ of Corti receptor cells (15,000 per ear) - inner hair cells (1 row) - outer hair cells (3 rows) 11 Cochlear Mechanics What does this wiring do????? - cochlea decomposes sounds into frequency components - i.e., does a Fourier transform hint - think vision - mechanical system that works with resonance properties - the traveling wave ....... Place on the basilar membrane gives the frequency Via the peak of the traveling wave.... 12 Auditory nerve Stimulation deafness - receptive fields - frequency selective Pathways cochlea auditory nerve cochlear nucleus superior olive lateral lemiscus inferior colliculus MGN temporal cortex Cortex - tonotopic map of frequency space AI - primary auditory cortex AAF - anterior auditory field - place in the basilar membrane. - place in the cortex = frequency It is both astonishing and confusing that more than 50 years of physiological research on the auditory cortex was not enough for a comprehensive characterization of the primary auditory field, to say nothing of the other fields. G. Ehret 1997 A fork in the road Animal versus human animals The problem of diversity in neurophysiology What they use their auditory system for..... The problem of language ..... and lateralization.... 13 ...
View Full Document

This note was uploaded on 04/13/2008 for the course CGS 2301 taught by Professor O'toole during the Fall '07 term at University of Texas at Dallas, Richardson.

Ask a homework question - tutors are online