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Lecture 14

Psychology 1000 Lecture Notes - Lecture 14: Retinal Ganglion Cell, Max Wertheimer, Visual Cortex


Department
Psychology
Course Code
PSYCH 1000
Professor
Dr.Mike
Lecture
14

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Perception
Lateral Inhibition
Visual Cortex
Gestalt Laws
Next Time: Perception II
Scan: Finish Chapter 5
How does lateral inhibition work?
different from retina
What are the Gestalt rules for perception?
High pitched sound
The neurons near the oval window are firing rapidly, while other neurns on the basilar
membrane are barely firing. Acoording to von Bekesy, this is interpreted by the individual’s
brain as:
Optic chiasma
When the effects last longer, they are in the level beyond retina
If a receptor cell receive light, and the horizontal cells inhibits the surrounding cells,
therefore receptive is created, explains why grey in white background seems darker than in
a black background, also explains phantom spots, because there are more surround
stimulation than the center, therefore we see dark smudges
Lateral inhibition
Insert recording electrode in a cat (or other animal)
retina response to slit of spots of light
o
Hubel & Wiesel: Retinal ganglion cells
Cortical cells may be orientation specific & motion sensitive
o
In the cortex, they don’t respond to dots of light, but instead respond to slits/lines of light
Recording from the visual cortex:
Lowest to highest
Classification of 3 cells
Fires to a slit at a particular orientation on a specific retinal location
usually vertical
if the orientation changes, the cell firing rate decreases or stop completely
this is caused by a vertically arranged retinal ganglion cells that are connected to the
simple cell, and only vertical lines can hit all the on center” simultaneously
Simple cell
they form a straight line
o
let’s say you have 5 cells
then you get no response from the single cells
!
the line might not hit the centre of the cells
o
they fire all at once when there is a vertical line
A vertical slit at a particular retinal address wouldhit all the centers
Retinal Ganglion Cells
Moving slits at a particular orientation
Complex cell
perpendicular lines, parallelogram
o
Combination of stimulus features
In frogs, they work for small dark, randomly moving objects in the visual field
o
For frogs, those objects are like food
o
Bug detectors
no one actually found them
o
hypothetical neuron that represents a complex but specific concept or object
o
activates when a person "sees, hears, or otherwise sensibly discriminates" a specific
entity, such as his or hergrandmother
o
Grandmother cells
Hyper complex cell
Theories of color vision: Trichromatic and opponent process
o
Color blindness
o
Color vision
EX) parts of ear, Place Theory vs. Frequency Theory, hearing loss
o
Hearing
General: touch, taste, smell
Stuff need to know
How do we understand and interpret the world?
Need to distinguish the figure from the ground
Perception
It is difficult to see it when the image is too degraded
EX) camouflage
!
We don’t know how to put them together
o
If the ground information is ruined
Typically not a problem, but…
Max Wertheimer
we don’t see them as alternating lines
EX) rows of filled dots and unfilled dots
"
People tends to group similar things together
!
Similarity
o
we see them as 3 groups, not 6 individual lines
EX) two lines placed closer, total 6
"
People tends to group close distance things together
!
Proximity
o
People do not like to see parts, but like to see the whole
!
Importance of expectation and context
!
Continuity
o
Physically connected = psychologically connected
!
Connectedness
o
See an image that is slightly broken
!
EX) a “broken triangle is looked like a perfect triangle
"
but we see it as a whole
!
Closure
o
we use some parts of the image, and create our imaginary lines
!
Subjective contours
o
Principles of grouping
If we expect to see an old women, we see it as old
o
If we expect young, we see young
o
Important of expectation and context
Gestalt approach
Lecture 14
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