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• Ganglion cells project to the brain via the optic nerve
• information is projected to contralateral cortex!
Visual Pathways
• the retina is mapped onto primary visual cortex
• called a retinotopic or spatiotopic map
Visual Pathways
Stimulus Cortical Activity
• signals are separated according to the type of information
Visual Pathways
Dorsal “Where” Pathway:
Motion and Location
Ventral “What” Pathway: Color and Form
Primary Visual Cortex
(V1)
Seeing
Seeing
• Seeing is the process of converting electromagnetic radiation into a conscious mental event
Seeing
• visual system faces many challenges– too much information– too little information– conflicting information– ambiguous information
Seeing
• too much information
Seeing
• too little information
Seeing
• Conflicting Information
Seeing
• Ambiguous information
Seeing
• We will consider two aspects of vision to explore how the brain overcomes these challenges:
– Seeing depth– Seeing in color
Seeing Depth
• What’s the big problem with seeing depth ?
Seeing Depth
• The world is 3D, the retina is 2D !
Depth Cues
• Four categories:1.Pictorial
2.Physiological
3.Motion
4.Stereoscopic
Depth Cues
Pictorial Depth Cues: aspects of 2D images that imply depth
Depth Cues
Pictorial Depth Cues: aspects of 2D images that imply depth Physiological Depth Cues: Proprioception in ocular muscles indicates
accommodation and convergence
Depth Cues
Pictorial Depth Cues: aspects of 2D images that imply depth Physiological Depth Cues: Proprioception in ocular muscles indicates
accommodation and convergence Motion Depth Cues: foreground and background move in opposite directions
Depth Cues
Pictorial Depth Cues: aspects of 2D images that imply depth Physiological Depth Cues: Proprioception in ocular muscles indicates
accommodation and convergence Motion Depth Cues: foreground and background move in opposite directions Stereoscopic Depth Cues: disparity between two retinal images indicates
distance
Pictorial Depth Cues
– Occlusion
Pictorial Depth Cues
– Occlusion
Pictorial Depth Cues
– Shadows and Shading
Pictorial Depth Cues
– Shadows and Shading
Pictorial Depth Cues
– Shadows and Shading: visual system assumes light from above
Pictorial Depth Cues
– Shadows and Shading: visual system assumes light from above
Pictorial Depth Cues
– Shadows and Shading
Pictorial Depth Cues
– Shadows and Shading
Pictorial Depth Cues
– Retinal image size– far objects smaller than near objects
• Retinal image size– problem: big far things same as close
small things– “solved” by size constancy: Perceived size
is adjusted according to perceived distance (based on other cues)
– forms the basis for several visual illusions
Pictorial Depth Cues
• Retinal image size
Pictorial Depth Cues
• Retinal image size
Pictorial Depth Cues
• Linear perspective
Pictorial Depth Cues
