Transcript lecture 4

PSYCH 2220
Sensation & Perception I
Lecture 4
Keywords for lecture 3
bipolar cells (excitatory and inhibitory types), retinal
ganglion cells, on-centre off-surround, off-centre onsurround, concentric organization, spontaneous firing
rate, excitation, inhibition, retinal ganglion cells as edge
detectors, Mach bands, "scalloped illusion",
simultaneous contrast, seeing (or not seeing) gradient (4
retinal ganglion cell demonstrations)
information passing down the optic nerve, optic chiasm,
magnification factor, partial decussation, thalamus,
cortex, brainstem, olfactory 'swelling', visual 'swelling',
hearing and balance 'swelling', lateral geniculate nucleus
of thalamus (perception), pupil control nucleus, superior
colliculus (fast eye movements), vestibular nucleus (slow
eye movements and orientation)
Keywords for lecture 3 (cont’d)
sustained and transient cells, cortex (cortices), cerebral
hemispheres, cerebellum, sulcus (sulci), gyrus (gyri),
functional localization over the cortex, primary sensory
projection areas, association cortex, frontal, parietal,
inferotemporal, visual cortex, area 17, Brodmann,
retinotopic map,
LEFT
VISUAL
FIELD
RIGHT
VISUAL
FIELD
OPTIC CHIASM
LEFT
BRAIN
RIGHT
BRAIN
LEFT
VISUAL
FIELD
RIGHT
VISUAL
FIELD
OPTIC CHIASM
THALAMUS
BRAIN STEM
pupil control centre
superior colliculus
vestibular area
Lateral geniculate nucleus of the THALAMUS
Organization of the lateral geniculate
of the THALAMUS (1)
Parvocellular
layers (3- 6)
Magnocellular
layers (1- 2)
6
6
5
5
4
4
3
3
2
2
1
Injection of
tracer to left eye
1
LATERAL GENICULATE NUCLEUS
1 Acts as a relay to the cortex
2 Keeps information from the two eyes separate
3 Has visual receptive fields that look just like the retina
4 Is retinotopically arranged
5 Is divided into layers:
6
5
4
3
2
1
LEFT
gets input from RIGHT eye
gets input from LEFT eye
RIGHT
1,2 Magnocellular layers
(Magno = big)
3-6 Parvocellular layers
(Parvo = small)
The visual system 6 - 8
CORTEX
Magnification factor
when looking at the centre, each letter uses
the same amount of cortex
David Hubel
Torsten Wiesel
Plotting the receptive field
of a simple cell…..
Hubel & Wiesel described three types of
cells in the cortex:
• simple
• complex
• hypercomplex
from their responses all vision is built up.
They received a NOBEL PRIZE for this work.
CELL TYPES IN THE PRIMARY
CORTEX:
SIMPLE CELLS
1 ... have receptive fields like this.
or
or
or
2 These fields could be made up from retinal
cells like this:
RECEPTIVE
FIELDS
ie
i
CELLS
e
Cortical cell
KEY:
i= inhibitory
e=excitatory
SIMPLE CELLS
are orientation tuned...
i
i
i
i
i
i i
i
ee
e e i
e e
e
i
e
e i
i
i i
WILL RESPOND
i i
e i
e
i
e e i
i e e
e
i
e
i
e i
i
i
i i
i
WILL NOT RESPOND
('e' & 'i' regions stimulated).
Response
Visual cortical cells are orientation tuned
preferred
orientation
Orientation
Complex cells
receptive field of
complex cell
will respond equally well to any of these
i
i
i
i
i
i i
i
e i
i e e
e
i
i e ei i i
e i ee i
ei
i
e i
e i e
i
i
ee
i i i i i e e ii
i
i
ei i e i
ee
e
i
i
i
i
e e i i i i ii e e i
e e ee i e e
e ii e
e e
ii e e i
i
e i e e
i
i e ii e i
e
i
i
i
i
e i i
ii i
i
receptive field of
complex cell
The visual system 6 - 13
receptive field
will not respond
will respond
will respond
The visual system 6 - 14
video about cortical cells
Tuning for orientation of bars
Tuning for width of bars
Activity profile while viewing the test stimulus
Activity profile while viewing the adapting stimulus…
the amount of adaptation depends on the activity
during this period..
Response before adaptation for each channel...
.. Is reduced depending on each channel’s adaptation.
The peak of the extrapolated curve…
.. Is thus shifted.
Hypothetical
channels
Amount of
adaptation
Structure and organization
of the cortex
Organization of a hypercolumn.
Orientation
pinwheels
Colour
blobs
RIGHT
EYE
LEFT
EYE
RIGHT
EYE
LEFT
EYE
Pinwheels in the cortex
Visualizing orientation columns in the cortex
(Using radioactive deoxyglucose)
Ocular dominance bands over the cortex
What happens beyond the
hypercomplex cells?
Grandmother cells
heirarchy
prosopagnosia
face cells; hand cells
anatomy
transient cells
magnocellular layers of LGN
parvocellular layers of LGN
sustained cells
Stimuli used to investigate processing of
cells in the inferotemporal region. The image of
the monkey’s hand elicited the largest
response….
...from a cell in the
Inferotemporal cortex
A face cell….
...from the Inferotemporal cortex
damage to the face cell area in
the inferotemporal cortex…
… causes PROSOPAGNOSIA.
A specific inability to recognize faces.
A group of sixteen cells, for example, could
code 2 16 (65,536) patterns even if each cell
could only be OFF or ON.
Hat
Eyes
Nose
Hair
Hat
Eyes
Nose
Hair
Hat
Eyes
Nose
Hair
Hat
Eyes
Nose
Hair
As promised .. The following is a
question that will appear on the
midterm next week… (no, I did not
promise to ANSWER it too….!
16 An ophthalmoscope is a device for
a)
measuring how far you can see in each direction
b)
looking at electrical waveforms
c)
for measuring the visual field
d)
looking into eyes
e)
investigating light adaptation
GOOD LUCK!
REVISION
Keywords for lecture 1
electromagnetic spectrum, (pit viper), mechanical energy,
chemical energy, stages of vision, (i) eye movements,
(ii) focus, (iii) light regulation, pupil, pin-hole camera,
refraction, focus, cornea, lens, accommodation,
myopia, hyperopia, astigmatism, presbyopia,
diving animals, (i) mask,
take out cornea on land and use powerful lens
(ii) flat cornea, (iii) pin-hole,
(iii) brute force solution: lens can go from ‘air-dwelling
type’ through to ‘water dwelling type’
(iv) four-eyed fish, (mermaids)
Keywords for lecture 2
depth of focus, ophthalmoscope, retina, retinal blood
vessels, fovea, optic disk, blind spot, retina,
cells, cell membrane, ions, potassium, sodium, channels
(meaning 1), neurones, resting potential (-70mV), action
potential, synapse, neurotransmitter, Schwann cells,
axon, dendrites, polarization, depolarization,
hyperpolarization,
dark/light adaptation, rods, thresholds, sensitivity, cones,
visual purple, Purkinje shift, scotopic, photopic, fovea,
receptive fields, bipolar cells, (excitatory and inhibitory
types), retinal ganglion cells, on-centre off-surround, offcentre on-surround, concentric organization
Keywords for lecture 3
retinal ganglion cells, on-centre off-surround, off-centre
on-surround, concentric organization, spontaneous firing
rate, excitation, inhibition, retinal ganglion cells as edge
detectors, Mach bands, "scalloped illusion",
simultaneous contrast, seeing (or not seeing) gradient (4
retinal ganglion cell demonstrations)
information passing down the optic nerve, optic chiasm,
magnification factor, partial decussation, thalamus,
cortex, brainstem, olfactory 'swelling', visual 'swelling',
hearing and balance 'swelling', lateral geniculate nucleus
of thalamus (perception), Edinger-Westphal nucleus
(pupil), superior colliculus (fast eye movements),
vestibular nucleus (slow eye movements)
Keywords for lecture 3 (cont’d)
lateral geniculate nucleus of thalamus, magnocellular
and parvocellular layers, sustained and transient cells,
cortex (cortices), cerebral hemispheres, cerebellum,
sulcus (sulci), gyrus (gyri), functional localization over
the cortex, phrenology, primary sensory projection areas,
association cortex, frontal, parietal, inferotemporal,
visual cortex, area 17, Brodmann, retinotopic map, Hubel
and Wiesel, simple cells,
Keywords for lecture 4
simple cell receptive fields, relation to retinal ganglion
cells, tuned for (i) orientation, (ii) width-of-bars,
(iii) movement, (iv) direction, binocular
complex cells, hypercomplex cells,
grandmother cell hypothesis, orientation columns,
hypercolumns, pinwheels, ocular dominance bands,
radioactive deoxyglucose, autoradiographs,
inferotemporal cortex (ventral stream), prosopagnosia,
parietal cortex (dorsal stream), tilt after effect, channels
(meaning 2), adaptation (psychophysical technique)
Left over keywords….
grandmother cell hypothesis,
orientation columns,
hypercolumns, pinwheels, ocular
dominance bands, radioactive
deoxyglucose, autoradiographs,
inferotemporal cortex (ventral
stream), prosopagnosia, parietal
cortex (dorsal stream), tilt after
effect, channels (meaning 2),
adaptation
(psychophysical technique)
There will be 37 multiple choices:
Total =
1 point each
37 points = 100%
Counts for 30% or 40% if it is your best.
A question from next week’s exam
14 A synapse is
a)
another name for a nerve cell or neurone
b)
the membrane on which the photopigment is stored in rods and
cones
c)
the gap between nerve cells across which they can communicate
d)
a cell that wraps itself around the axon of a neurone
e)
none of the above