08b vision processing form and shape shortPresentation Transcript
Visual Signal Processing Hubel Wiesel
Neuronal architecture of mammalian visual system
Retina Functional organization
Anatomical Distribution of Rods and Cones
Receptive Field Receptive fields of photoreceptors and their connections. (A) The receptive field center provides a direct input from the photoreceptors to the bipolar cell, and the receptive field surround provides indirect input from the photoreceptor to the bipolar cells via horizontal cells. (B) 1: Photoreceptor cell; 2: on-center bipolar cell; 3: off-center bipolar cell; 4: on-center ganglion cell; 5: off-center ganglion cell.
Receptive field of Retina
Ganglion Cell : Contrast discrimination
Receptive field of bipolar and ganglion cells
Ganglion Cells Characteristics M Cells P Cells Color No Yes Contrast High Low Spatial Low High Temporal High Low Population 5% 90% Action Potential Phasic, fast Tonic, slow Function Movement Shape Receptive field Large Small Retinal mapping Periphery Fovea
Central Projections of Retinal Ganglion Cells
Lateral Geniculate Ganglia
Retinal projection to Lateral Geniculate Nucleus
Central retinal pathway
LGN Projection to Occipital Cortex
Primary Visual Cortex information flow
The Primary Visual Cortex
The ocular dominance columns
Ocular Dominance Column input from LGN R L
The overlap and blurring of ocular-dominance columns beyond layer 4 is due to horizontal or diagonal connections.
Orientation column of visual cortex: Optical imaging
Organization of Blobs in visual cortex
Primary Visual Cortex Architecture
Receptive field of a simple cell in the primary visual cortex
Simple cell of visual cortex
What Primary Visual Cortex do?
Projection of LGN to V1
A, sends a signal to many simple cells, each with different orientations. In this figure, cell A shares its information with 3 simple cells. If there were a simple cell for each 5 deg change in orientation, the same cell A would provide information to 36 simple cells (180 deg/ 5 deg = 36).
Retinal image of an object
Significance of Movement Cells
A rough indication of physiological cell types found in the different layers of the striate cortex.
Hypercomplex Cells End Stopping cells
V2-3: Assembling simple features into objects. V1 V2
What we perceive depends not only on the visual image but also on our interpretation of what we see Interpretation based on our memories modifies what we see. For example if we expect to see the letter m in “exanple” we may not notice that is has been misspelled.
AIT = anterior inferior temporal area; CIT = central inferior temporal area; LIP = lateral intraparietal area; Magno = magnocellular layers of the lateral geniculate nucleus; MST = medial superior temporal area; MT = middle temporal area; Parvo = parvocellular layers of the lateral geniculate nucleus; PIT = posterior inferior temporal area; VIP = ventral intraparietal area.) (Based on Merigan and Maunsell 1993.)
Inferior Temporal neuron response to Form
Face and Complex Form Recognition ITC
Fusiform face area
Columnar organization of IT area
IT has a columnar organization Cells within a column are activated by the same object. Neighboring columns respond best to objects of a similar shape as in a and b.