Download 9 visual-pathways

Functional specialization
Phrenology
Franz Joseph Gall
(1757-1828)
from Webster’s Academic Dictionary, 1895
Macaque visual areas
Flattening
the brain
Human visual
cortical areas
IPS2
IPS1
V7
V3A/B
V2
IPS2
IPS1
V7
V2
LO2
LO1
MT
V1
V3 V4
V3
V3A/B
LO1 LO2
MT
V4
Functional specialization
Match each cortical area to its corresponding function:
V1
V2
V3
V3A
V3B
V4
V5
V7
LO1
IPS1
IPS2
Etc.
Motion
Stereo
Color
Texture
Segmentation, grouping
Recognition
Attention
Working memory
Mental imagery
Decision-making
Sensorimotor integration
Etc.
Defining visual cortical areas
PhACT
Physiology
Architecture
Connections
Physiology
Example: direction selectivity in V1
Cytoarchitecture: Brodmann’s areas
Korbinian Brodmann
(1868-1918)
~50 cytoarchitectural areas
defined by cell size, cell density,
number of layers, density of
myelinated axons.
Topography
Different stains for different features
Golgi stain: small fraction of
cell bodies and dendrites
Nissel stain: only cell bodies
Weigert myelin stain for
axons
Cortical layers
Primary visual cortex slice (Nissl stain)
Cytoarchitecture and function
layer 4: input
layer 5: output
Motor cortex: expanded
layer 5, reduced layer 4
Primary visual cortex:
expanded layer 4 with
three sublayers
Brodmann areas and functional modalities
Brodmann areas
correspond coarsely
to functional modalities
Brodmann areas do not correspond
exactly to functional areas
Brodmann areas superimposed
Functional areas in monkey brain
Architecture
V2: stripes
V1: blobs/puffs
MT: dense
Example: cytochrome oxidase staining in human visual cortex
Connections: white matter bundles
Superior longitudinal
(arcuate): connects language
centers (Broca’s, Wernicke’s).
Superior occipitofrontal:
dorsal (where) visual pathway.
Inferior occipitofrontal:
ventral (what) visual pathway.
Tracing connections with
diffusion tensor imaging
Low magnification
Tracing connections
High magnification
Injection site in LGN (rat)
Retrograde tracer
(horseradish peroxidase)
Retina
Connections: laminar
organization
S: supragranular origin
I: infragranular origin
B: bilaminar origin
(no more than 70%-30% split)
F: layer 4 termination
C: columnar termination
(equal density in all layers)
M: multilaminar termination
(avoids layer 4)
Connections:
hierarchical
organization of
visual areas
monkey visual cortex
Hierarchical
organization
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Line thickness
represents a loose
estimate of
connection strength
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Topography
IPS2
IPS1
V7
V2
V3
V3A/B
LO1 LO2
MT+
V4
Each visual brain area contains a map of the visual world and
performs a different function.
Retinotopy (human V1)
Visual Disturbances Following
Gunshot Wounds of the Cortical
Visual Area
Based on observations of the wounded in
the recent Japanese wars
German edition first published in 1909
Tatsuji Inouye
(1880-1976)
V1 retinotopy
Upper VM
HM
Lower VM
80
V1 topography &
magnification
Cortical magnification
Retinal image
Cortical map
Retinotopy (monkey V1)
Cortical representation
measured with 2-deoxy-glucose
stimulus
flattened left hemisphere
1 cm
2-deoxyglucose
Tootell et al. (1988)
Measuring human retinotopic
maps non-invasively
Radial component
Angular component
Retinotopy: radial component
1 cm
1 cm
Human
Monkey
Retinotopy: angular component
Human
1 cm
1 cm
Monkey
Visual areas
Human
1 cm
1 cm
Monkey
Flattening the human brain
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Cortical segmentation & flattening
Retinotopy: angular component
dorsal
V7
V3A/B
V3d
V2d
medial
LO1
LO2
MT
lateral
V1
V2v V3v
V4
ventral
Human visual
cortical areas
IPS2
IPS1
V7
V3A/B
V2
IPS2
IPS1
V1
V7
V2
LO2
LO1
MT
V3 V4
V3
V3A/B
LO1 LO2
MT
V4
Monkey visual areas from fMRI
V1
V2
V3
V3A
V4
MT
Topography: columnar
architecture in V1
Retinotopic map
Columnar architecture
1 mm
Columnar architecture
Perpendicular electrode penetration:
same orientation preferences and
ocular dominance.
Surface
Tangential electrode
penetration: orientation
preference and/or
ocular dominance varies.
White matter
Ocular dominance columns
Optical imaging apparatus
Reference image
Functional difference image
Ocular dominance movie
Orientation columns and pinwheels
Human ocular dominance columns
Amblyopia
Columnar architecture in other
visual cortical areas
Fujita, Tanaka, Ito, Cheng,
Nature (1992)
Albright, Desimone, Gross,
J Neurophysiol (1984)
Direction columns in MT
Functional
specialization
“Feature” columns in IT
Parallel visual
pathways
Dorsal & ventral
streams: what vs.
where
Normal observer’s brain
Dorsal & ventral
streams: action vs.
perception
Lateral Occipital area
(area LO) activation
DF’s brain
area LO
lesion
Intact Line Drawings
versus scrambled
Each image presented for 4 s
with 12-s ISI
Control
DF
Increasing receptive field size
Increasingly complex selectivity
STS
MST
MT
V3A
V3
V2
MT
Increasing invariance
MST
STS