PSY 305 Lecture Notes - Lecture 5: Railways Act 1921, Necker Cube, Artificial Neural Network
29 Jun 2018
School
Department
Course
Professor
Psychology 305
Week 3, Class 1
10 October 2017
Lecture Notes
Quiz next class: not comprehensive, only material since last quiz.
The Perceptual Brain
● Modules: faces, places, movement, etc
● Maps: magnification factor
● Columns: location, orientation, ocular dominance
● Streams: what, where/how
The Primary Visual Cortex
● Edge detectors: the receptive fields of the primary visual cortex (V1) are lines of
particular orientations
● Parallel processing in V1: because of their different receptive fields, the neurons in
area V1 are each specialized for a particular kind of analysis, which can occur at the
same time
Processing in the visual system
● Parallel processing is also demonstrated at higher visual pathways
○ Where or how pathway moves up the back and over the top of the brain
○ What pathway moves across the side of the brain
● From area V1, information is sent to many secondary cortical visual areas for further
parallel processing
● The what stream:
○ Concerned with the identification of objects
○ Involves an occipital-temporal pathway
○ Damage to this system can result in visual agnostic
● The where stream:
○ Is concerned with determining the locations of objects and guiding our actions in
response
○ Involves an occipital-parietal pathway
○ Damage to this system can result in problems with reaching for seen objects
● INTENSE INTERCONNECTIVITY BETWEEN THE TWO!!!!!
Block Diagram of Monkey Visual Processing Areas
● Modularity: different regions of extrastriate cortex process different aspects of the visual
image
● A ton of lines and connections between them
The Big Picture
● With the great extent of parallel processing in the visual system, different aspects of a
single object (e.g. Shape, color, movement) are analyzed in different parts of the visual
system
● How the brain reunites these different features into a coherent, integrated perception of
the objects in the visual scene is referred to as the binding problem
Feature Integration Theory
● Triesman and Gelade (1980)
○ Preattentive stage
- features of objects are separated
○ Focused attention stage
features are bound into a coherent perception
○ Role of attention
- attention may serve as the “glue” between the physiology of
the what and where streams
● Object → preattentive stage (features separated) → focused attention stage (features
combined) → perception
● If we don't allow enough processing time, we have issues
○ E.g. Conjunction errors
○ “TPUM” flashed on screen is likely to be misread as “TRUM” or even “DRUM”
Form Perception
● The Necker Cube is an example of perception going “beyond the information given”
○ Two different perceptions of depth are possible, given the lines on the page.
● An early 20th century movement known as Gestalt psychology captured this ideas as
“the whole is different from the sum of its parts”
Object Perception Required Construction
● The Gestalt Principles of stimulus organization account for some of the brain’s
perceptions of the world
○ Those perceptions involve cues about similarity, proximity, form, figure and
background properties, shading, and meaningfulness.
○ Proximity:
the closer 2 figures are to each other, the more likely we are to group
them and see them as part of the same object
○ Similarity:
we tend to group figures according to how closely they resemble each
other (color and shape)
○ Good continuation
: we tend to interpret intersections lines as continuous
■ Can create cool illusions with this
■ In this drawing by the vision scientists Peter Tse, two cats appear to be
one cat wrapped around the bar. You have the lesion of one continuous
cat even though you know the cat is unlikely to be so long.
○ Closure:
we tend to complete figures even when gaps exist
○ Illusory contours:
we tend to perceive contours even when they do not exist
Form Perception
● In the Face-Vase figure, two interpretations are possible, each based on a different
figure/ground segregation.
○ You either see two faces or one vase
● These examples might suggest that perception proceeds in two stages:
○ One where visual features are processed
○ And a later stage in which perception goes “beyond the information given”
● However, this view presumes serial processing, not the parallel processing that
characterizes the visual system
Document Summary
Quiz next class: not comprehensive, only material since last quiz. Edge detectors: the receptive fields of the primary visual cortex (v1) are lines of. Parallel processing in v1: because of their different receptive fields, the neurons in area v1 are each specialized for a particular kind of analysis, which can occur at the same time particular orientations. Parallel processing is also demonstrated at higher visual pathways. Where or how pathway moves up the back and over the top of the brain. What pathway moves across the side of the brain. From area v1, information is sent to many secondary cortical visual areas for further parallel processing. Damage to this system can result in visual agnostic. Is concerned with determining the locations of objects and guiding our actions in response. Damage to this system can result in problems with reaching for seen objects. Modularity: different regions of extrastriate cortex process different aspects of the visual.
