Kuffler’s Cat
Sensation and Perception - sensory2.ppt © 2001 Laura Snodgrass, Ph.D.
Kuffler’s findings
• Concentric receptive field organization
– central disk with annulus
• Center-surround antagonism
– an excitatory center will always an inhibitory
surround
– an inhibitory center will always have an
excitatory surround
Sensation and Perception - sensory2.ppt © 2001 Laura Snodgrass, Ph.D.
Hubel & Wiesel’s Monkey
Sensation and Perception - sensory2.ppt © 2001 Laura Snodgrass, Ph.D.
Hubel & Wiesel’s Findings
• Spot detector
– cell fires maximally when only the excitatory
region is covered - precoded for a critical
feature
• Ignoring steady state
– when entire field is covered the excitation and
inhibition balance and the cell fires at the
spontaneous rate, just as if nothing was there.
Sensation and Perception - sensory2.ppt © 2001 Laura Snodgrass, Ph.D.
Hubel & Wiesel’s Hierarchy of Cells
• Hierarchy of feature detectors all precoded for critical
features
• The shape of the receptive field determines the feature the
cell is designed to detect
Sensation and Perception - sensory2.ppt © 2001 Laura Snodgrass, Ph.D.
The Hierarchy
• In LGN - spot detectors
• In Occipital Lobe
– area 17 - simple cells = oriented line detectors
– area 18 - complex cells = motion detcetors
– area 19 - hypercomplex cells = angles, lengths,
curves, edges
• In Temporal Lobe
– gnostic units
Sensation and Perception - sensory2.ppt © 2001 Laura Snodgrass, Ph.D.
Sensory Coding
• How do the “on” and “off” responses of cells
represent properties of the environment?
• Two properties to represent:
– magnitude - how much is out there?
– quality - what is it?
Sensation and Perception - sensory2.ppt © 2001 Laura Snodgrass, Ph.D.
Magnitude - Three Mechanisms
• As magnitude increases firing rate increases
– to a limit (1,000/sec)
• Volley theory
– cells fire in a sequence
• Other nerves take over
– e.g. rods to cones; inner to outer hair cells
Sensation and Perception - sensory2.ppt © 2001 Laura Snodgrass, Ph.D.
Quality - Three Mechanisms
• Muller’s Doctorine of Specific Nerve Energies
• Specificity
– specific receptors for specific sensations
– e.g. Pacinian corpuscle for deep pressure
• Across fiber pattern theory
– pattern of activity across many receptors
– e.g. taste; color
Sensation and Perception - sensory2.ppt © 2001 Laura Snodgrass, Ph.D.