Transcript PY262.10.HigherCortical

The visual system The visual systems
eye
thalamus
visual cortex
lateral geniculate nucleus
(LGN)
Extrastriate
cortex
Occipital Striate Cortex
Extrastriate Cortex: secondary cortical
areas communicated to & from striatal
cortex (V1 - primary receptive areas)
Ungerleider and Mishkin (1981)
Copyright © 2002 Wadsworth Group. Wadsworth is an imprint of the
Wadsworth Group, a division of Thomson Learning
Top = Dorsal
Bottom = Ventral
From “Object Vision and Spatial Vision: Two Central Pathways,” by M. Mishkin, L. G. Ungerleider & K. A.
Makco, 1983, Trends in Neuroscience, 6, 414-417, figure 1. Copyright ©1983 Elsevier Science
Publishers B. V. Reprinted by permission.
Ungerleider and Mishkin (1981)
Copyright © 2002 Wadsworth Group. Wadsworth is an imprint of the
Wadsworth Group, a division of Thomson Learning
Remove Parietal lobe = couldn’t identify location
Remove Temporal lobe = couldn’t identify object
Figure 4.26 The two types of discrimination tasks used by Ungerleider and Mishkin. (a) Object
discrimination: Pick the correct shape. Lesioning the temporal lobe (shaded area) makes this task difficult.
(b) Landmark discrimination: Pick the food well closer to the cylinder. Lesioning the parietal lobe makes this
task difficult. (From Mishkin, Ungerleider, & Macko, 1983.)
See pages 93-96 in chapter 4 of text
object
discrimination
monkeys' performance impaired after lesion to temporal
lobe (“What pathway”), but not after lesion to parietal lobe
(“Where pathway”)
landmark task
monkeys' performance impaired after lesion to parietal lobe
(“Where pathway”), but not after temporal lesion (“What
pathway”)
Processing in Extrastriate Visual Cortex
Milner and Goodale
- patient "D.F." - damage to ventral stream
can not recognize objects,
= visual agnosia
but can interact with them
- patient "V.K." - damage to the dorsal stream
- can identify objects, but did not interact with them
appropriately
temporal stream parietal stream -
"What" pathway
Both “Where” &
"How" pathway
Figure 4.8, page 114
Visual pathway
Movement
Copyright © 2002 Wadsworth Group. Wadsworth is an imprint of the
Wadsworth Group, a division of Thomson Learning
Medial Temporal Cortex
(Both Temporal
Lobe)
Form, depth, color
Inferotemporal Cortex
V1 = Striate Cortex
Medial temporal Cortex (Area MT)
Specialized for Visual Motion
Lesion Experiments
motion-blind patient - motion agnosia or
Akinetopsia
http://www.sockshare.com/file/8971FC52E214244A#
•Thank you LeighAnn
Medial temporal Cortex (Area MT)
Specialized for Visual Motion
Newsome and others
100% correlation
0% correlation
50% correlation
normal threshold = 1-2%
threshold after lesions of MT = 10-20%
Inferotemporal cortex (IT) - Complex form Processing
Tanaka, et al., 1991: receptive fields “respond best”
to different specific forms
Two types of cells
found in the IT:
1. “Primary Cells”:
respond to slits,
spots, ellipses &
squares
2. “Elaborate Cells”:
respond to specific
complex shapes (and
influenced by color &
texture)
Neighboring columns in the Inferotemporal
Cortex (IT) have cells that respond to stimuli
that share similar features
“Fusiform Face Area” (FFA) of the Inferotemporal (IT)
Cortex: cells responsive to faces
Some cells respond best to profiles of faces
= view-specific cells
(other cells showed view-invariance)
Identity!!!
Figure 4.24, page 129
Gauthier et al.
(1999) -Greebles
Copyright © 2002 Wadsworth Group. Wadsworth is an imprint of the
Wadsworth Group, a division of Thomson Learning
Human adults come
to recognized specific
Greeble faces with
training.
fMRI activity
correlates Fusiform
Face Area of
Inferotemporal lobe
with Greeble
recognition
IT neuron properties; built in or experience?
- probably both
- five week old infant monkeys have faceselective neurons (“built in” through Natural
Selection)
- Logothetis and Pauls - trained monkeys to
complex shapes of a particular orientation
-subsequently found cells in IT that were tuned
to that object and that orientation
Tarr & Gauthier (2000) – measurement of FFA to
non-face, but experienced stimuli?
Cells fired to car
pictures for car experts
Cells fired to bird pictures
for bird experts
Pierce, Haist, Sedaghat, & Courchesne (2004) –
measurement of FFA in individuals diagnosed with Autism?
• Initial finding: firing patterns in the FFA (with fMRI) are
different from “typical” control subjects
– Question about do they not process the face because of damage to
FFA, or…
– Do they not have typical firing in FFA because they don’t look at
faces (chicken and egg problem)?
• Tested FFA activity to highly familiar faces (their mom)
– FFA activation looked like controls to mom and other highly familiar
faces (i.e., co-workers)
– When novel faces were mixed in with familiar faces, the FFA
activated more like “typical controls”
• Conclusion: cortical areas of the brain (i.e., IT-FFA) are
“experience dependent” – they re-organizes with experience
(referred to as “brain plasticity”)
Summary of the Inferotemporal lobe and “object
recognition”
• Organized in columns
• Cells in each column have similar “preferences” for
activation
• Primary cells (slits, spots, squares of light)
• Elaborate cells (complex shape, color, texture)
• Some columns respond to faces (call FFA)
• FFA may have an evolutionary “edge,” but experience is
essential
– FFA cells can be “taught” to fire to previously novel stimuli
with experience
– FFA cells are “expert” cells
Putting the parts together: The “Binding problem”
• Seeing red car in motion?
– Ganglion cells from cones (fovea) and/or rods (periphery) offer color,
movement, location information
– LGN cells from differing eyes, movement, form, color & where on the
retina
– V1 striate cortex magnify & locate (retinotopic) the car, and offer
form (i.e., spatial frequency) information
– Inferotemporal lobe processing FORM
– Medial temporal lobe processing MOTION
– Extrastriatal area V4 processing COLOR
– Multiple sites are simultaneously activated at each level (Ganglion,
LGN, V1, IT, MT, V4, etc., etc.)
 How do we put this all together to perceive a red CAR driving
down the road???
Figure 4.8, page 114
Visual pathway
Moving Car: all areas are “humming at once”
Copyright © 2002 Wadsworth Group. Wadsworth is an imprint of the
Wadsworth Group, a division of Thomson Learning
Medial Temporal Cortex
(Both Temporal
Lobe)
Inferotemporal Cortex
Associative Learning
Classical conditioning: Pavlov’s dog
Unconditioned stimulus (US):
Ring a bell
Unconditioned response (UR):
salivation when dog eats
Conditioned stimulus (CS):
Pair together:
Ring the bell just
before giving the
food
Ring a bell
Conditioned response (CR):
salivation when dog hears bell
We've Pulled the Stimulus Apart, How do we put
the Perception of the “event” together?
synchronous oscillations
Two neurons
firing in an “out of
synch” manner
A neuron bursting
at regular intervals
= oscillation
Two neurons “oscillating”
(bursting) synchronously