Transcript Chapter 2 figures 2.7 to 2.12

Figure 2.7. Number of neural impulses in selected single cells of the
monkey brain when shown differing pictures. These neurons fire the
most when a face is present (Washmuth et al. 1994).
Figure 2.8. (a) Rembrandt van Rijn, Anatomy Lesson of Dr. Tulp, 1632. Oil on
canvas, 162 cm x 217 cm. Mauritshuis, The Hague.
(b) Eye tracking diagram from Molnar (1981).
Figure 2.9. (a) Image with 4 bands of differing brightness. A to D are locations marks.
(b) Physical brightness levels of image in (a).
(c) Perceptual brightness of image (a) "seen" by viewer resulting from lateral inhibition.
(d) Conceptual diagram of how lateral inhibition can enhance borders between parts of the
visual field of different brightness (Goldstein, 2002). Here A to F refer to cells. Cells A, B,
and C faithfully convey greater brightness (100 units) than cells D, E, and F (20 units) to the
neurons directly behind them in the next layer. All cells send neural inhibition in proportion
to the brightness levels (10%) to cells situated next door in the next neural layer (i.e.,
laterally). The output at the next layer of neurons (bottom in figure) has a slightly brighter
"hairline" on the brighter side of the image(88 vs 80 units); and a slightly darker "hairline"
on the darker side (8 vs 16 units). The units of brightness were selected as an example.
Stimulus image
Light
Left visual Field – light
goes to right side of
retinas
Right Visual Field –
light goes to left side
of retinas
Retinas
with 3
layers of
Retinas
neurons
Optic nerves –
axons of ganglion
cells that are
located in retinas
The Thalamus, a
subcortical
structure. Visual
information passes
through the lateral
geniculate nucleus
of the thalamus.
Occipital lobes of
Cortex, 1st place in
cortex receiving
information about
visual scene; called
V1 (Vision 1).
Figure 2.10. Drawing of the visual system.
Visual Pathway – Simplified
LIGHT reflected
from the image
EYE – mechanical parts
(e.g., lens, fluid in eye-ball)
RETINA of EYE (neural parts - lining at back)
Layer 1: RECEPTORS
Layer 2: BIPOLAR CELLS
Layer 3: GANGLION CELLS
(axons form optic nerve to brain)
BRAIN
1st Nucleus in THALAMUS (mid-brain structure)
lateral geniculate nucleus
nd
2 CORTEX
a. Striate cortex at back of brain –V1
b. 2 Streams
Ventral: Inferior-temporal
(IT – around sides of brain)
Dorsal: Medial-temporal
(MT – up over middle of brain)
Passing light
representing
image faithfully
Change light to
neural impulses
Integrate light
info – (e.g.,
enhance edges)
Integrate
vision with
other senses
Receive info
in higher brain
What is seen
Where is
object
Figure 2.11. Verbal description of steps in the visual pathway.
Two Visual Streams in Cortex
What stream - Object identity
•Shapes of Objects and Colors recognized here
•Ventral route (around sides of brain)
• Pathway: V1 to V2 to V3 to V4 to Inferior Temporal (IT)
lobe
• Animals without IT cannot do task to discriminate between
two objects (food under a circular shape; not under a square).
•Humans with damage in what path cannot name objects they
see.
Where/How stream – Motion and Action
•Spatial arrangement, motion, depth recognized here
•Dorsal route (over top of brain)
•Pathway: V1 to V2 to V3 to V5 = Medial Temporal (MT) lobe
•Animals without MT cannot do task based on locatio (left bin
has the food).
•Humans with damage in the Where/How path cannot do
spatial tasks such as setting a table.
Figure 2.12. Two streams of neural information about vision in cortex
that are postulated by neuroscientists.