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The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system
1. Structure of the eye
2. Neural responses to light
3. Brightness perception & visual acuity
4. Spatial frequency analysis & spatial context
5. Form perception (psychological)
6. Visual pathways & visual cortex (humans)
7. Visual System & form perception (macaque)
The primate visual system Helmuth Radrich, 24.06.2004
Visible spectrum
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
The crystalline lens
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
The fovea
The primate visual system Helmuth Radrich, 24.06.2004
Rods and cones distribution
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
Information flow from eye to brain
• Via optic nerve• Data is not “raw”… preprocessed by retina• Human eye:
– 120 million rods– 5 million cones– Another few millions of bipolar/amacrine/horizontal cells– Optic nerver: 1 million axons
=> A single ganglion cell axon receives information from many receptors in a region of the retina defining the cells receptive field
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system
1. Structure of the eye
2. Neural responses to light
3. Brightness perception & visual acuity
4. Spatial frequency analysis & spatial context
5. Form perception (psychological)
6. Visual pathways & visual cortex (humans)
7. Visual System & form perception (macaque)
The primate visual system Helmuth Radrich, 24.06.2004
Neural response types
The primate visual system Helmuth Radrich, 24.06.2004
Receptive fields
The primate visual system Helmuth Radrich, 24.06.2004
Parvo and magno cells
The primate visual system Helmuth Radrich, 24.06.2004
Parvo and magno cells
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system
1. Structure of the eye
2. Neural responses to light
3. Brightness perception & visual acuity
4. Spatial frequency analysis & spatial context
5. Form perception (psychological)
6. Visual pathways & visual cortex (humans)
7. Visual System & form perception (macaque)
The primate visual system Helmuth Radrich, 24.06.2004
Intensity & perceived brightness
The primate visual system Helmuth Radrich, 24.06.2004
Dark adaptation
The primate visual system Helmuth Radrich, 24.06.2004
Relative sensitivity (wavelength)
The primate visual system Helmuth Radrich, 24.06.2004
Visual angle
The primate visual system Helmuth Radrich, 24.06.2004
Visual acuity
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system
1. Structure of the eye
2. Neural responses to light
3. Brightness perception & visual acuity
4. Spatial frequency analysis&spatial context
5. Form perception (psychological)
6. Visual pathways & visual cortex (humans)
7. Visual System & form perception (macaque)
The primate visual system Helmuth Radrich, 24.06.2004
Light distributions
The primate visual system Helmuth Radrich, 24.06.2004
Approximation of square waves
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
Apparent brightness
The primate visual system Helmuth Radrich, 24.06.2004
Modulation transfer function
The primate visual system Helmuth Radrich, 24.06.2004
Frequency analysis (biological)
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
Spatial context (lat. inhibition)
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
Temporal context effects
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system
1. Structure of the eye
2. Neural responses to light
3. Brightness perception & visual acuity
4. Spatial frequency analysis & spatial context
5. Form perception (psychological)
6. Visual pathways & visual cortex (humans)
7. Visual System & form perception (macaque)
The primate visual system Helmuth Radrich, 24.06.2004
Properties of visual environment
The primate visual system Helmuth Radrich, 24.06.2004
Masking
The primate visual system Helmuth Radrich, 24.06.2004
Feature extraction
The primate visual system Helmuth Radrich, 24.06.2004
Emergent features
The primate visual system Helmuth Radrich, 24.06.2004
Figure and ground
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
Subjective contours
The primate visual system Helmuth Radrich, 24.06.2004
Figural grouping
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
Texture defined grouping
The primate visual system Helmuth Radrich, 24.06.2004
Spatial frequency grouping
The primate visual system Helmuth Radrich, 24.06.2004
Good figures
The primate visual system Helmuth Radrich, 24.06.2004
Good figures
The primate visual system Helmuth Radrich, 24.06.2004
Good figures
The primate visual system Helmuth Radrich, 24.06.2004
What is this???
The primate visual system Helmuth Radrich, 24.06.2004
Conceptually driven processing
The primate visual system Helmuth Radrich, 24.06.2004
Global vs. local processing
The primate visual system Helmuth Radrich, 24.06.2004
Context and identification
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system
1. Structure of the eye
2. Neural responses to light
3. Brightness perception & visual acuity
4. Spatial frequency analysis & spatial context
5. Form perception (psychological)
6. Visual pathways & visual cortex (humans)
7. Visual System & form perception (macaque)
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
Receptive fields (simple cortical)
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
Layer of V1
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
Visual pathways (human)
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system
1. Structure of the eye
2. Neural responses to light
3. Brightness perception & visual acuity
4. Spatial frequency analysis & spatial context
5. Form perception (psychological)
6. Visual pathways & visual cortex (humans)
7. Visual System & form perception (macaque monkey)
The primate visual system Helmuth Radrich, 24.06.2004
Oram&Prett proposal
• Neurobiological data form macaque monkeys
• Analogies to human visual system
Object recognition as series of 4 computational stages in 7 major hierarchically arranged processing areas
Simple feed-forward network sufficient for computer simulation
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
• like in humans two major processing streams (only form perception is discussed)
• strong similarities to human brain
• Interconnection not as complete as it could be
Why????
Combinatorial explosion if object is to be recognized from simple features (only edges, etc.)
Basic edges etc. information not helpful in complex feature recognition at higher level
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
Min.-timings in information-stream
Assumptions (biologically plausible):
• about 5 ms to trigger firing in the next neuron + some ms for signal transmission inside neurons (minimum)
With the experimentally measured timings for the arrival of the first reactions in STPa after stimulus presentation (above):
Only 7 interneuron connections can lay on the way of the signal (correspond to biological layers of the visual cortex)
No time for lateral inhibition or feedback processes to interact with the information processing
Feed-forward only model is plausible, but only half of the story in higher perception
The primate visual system Helmuth Radrich, 24.06.2004
The primate visual system Helmuth Radrich, 24.06.2004
Reference
• Coren, S., Ward, L. M. and Enns, J. T. (1993). Sensation and perception
• Oram M. W. and Prrett, D. I. (1994), Modeling visual cognition from neurobiological constraints. Neural Networks 7 (6/7), 945-972
The primate visual system Helmuth Radrich, 24.06.2004
The END
Thank you for your attention!
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