Sensation and Perception Part 2 Flashcards
What does shape perception depend on?
Feature detector cells
What are receptor cells?
Receptor Cells are specialised cells that respond to certain characteristics of the stimulus such as curves and straight edges.
Different receptor cells respond to different ______.
lines
Optimal input for each cell, defines what?
it defines the cell’s receptive field.
Hubel and Wiesel studied _____ _____ on a cat.
receptive fields
Anesthetized cat had one eye propped open so that a series of visual _____ (lines with different ______) could be directed to particular regions of its _______.
stimuli, orientations, retina
A micro-electrode was implanted in the cat’s visual cortex to do what?
To monitor a single cell’s firing rates in response to the lines.
When the cells fired, its neural impulses were amplified, then displayed on an _______.
oscilloscope
What were the conclusions of Hubel and Wiesel’s cat receptive field study?
- Each neuron in the visual cortex has a “target” stimulus that evokes especially rapid firing
- These cells respond to the preferred line/edge the most
In cats and monkeys, features detectors in ____ seem to respond most when a ____ or edge of a specific ________ is in view.
V1, line, orientation
Other cells assemble elements in order to detect more ______ patterns (see the full ____).
complex, full
What does form recognition of form begin with?
The detection of simple features.
When recognition of form gets more complex, what does it depend on?
It depends on how the perceiver has organised the features (eg. colour- red/green and shape- straight?horizontal line, target=red horizontal line with the distractors)
Analysis of features (feature analysis) depends on a preliminary step in which the viewer must ______ the figure.
organise
We need to identify what the object of _____ is and then _______ the object of interest.
interest, segregate
The features of an object also determine how the viewer perceives the figure, give two examples of this.
T Junction = corner disappears from view
Y Junction = corner coming towards us
There are 5 ______ principles of Organisation.
Gestalt
Name the 5 principles of Gestalt Organisation.
Similarity Proximity Good Continuation Closure Simplicity
Explain Similarity.
We tend to group objects according to their similarities eg. we group dots in vertical rows as they are the same colour (red and blue) instead of horizontal rows as the colours alternate this way.
Explain Proximity.
We tend to perceive groups, linking dots that are close together.
When we perceive a continuous green bar behind a cylinder instead of two smaller rectangles this is known as _______ ________.
Good Continuation
When we perceive an intact shape, even when some parts are missing, what is this known as?
Closure
Explain Simplicity.
We tend to interpret a form in the simplest way possible. eg. we see two crossing rectangles instead of a 12-sided irregular polygon :)
To organise input, the perceiver must first _____ the visual scene.
analyse
Recognition of form begins with the detection of _____ __________.
simple features.
We have an ____ role in interpreting our surroundings..
active
A _____ _____ model guides identification of the process of detecting simple features works.
feature net
The model of perception is known as a ___ model.
network
Name the network models/processing of perception.
Bottom Up and Top Down
_____ detectors respond to very basic stimuli.
feature
Describe the bottom up processing.
Feature Detectors respond to very basic stimuli eg. curved lines
Then send input to more complex detectors that respond to a combination of features eg. letter detectors
And then again eg. to word detectors
Top Down and Bottom Up processing can be known as ___________ ________.
Bi-directional Activation
What 2 things do perception networks rely on?
Knowledge-Driven as well as Data-Driven processes.
What is the data-driven processing known as?
Bottom Up processing
What is the knowledge-driven processing known as?
Top Down Processing
Explain Top Down Processing.
1st we formulate a hypothesis about the identity of the stimulus.
We then select and examine relevant aspects of the stimulus to check the hypothesis.
Name this processing:
- Detect features of input
- Combine features into more complex forms
Bottom Up Processing
What do the underlying neural processes of perception involve?
Specialised Sub-systems
Evidence of perception is in the form of ____ processes.
neural
Name the 2 specialised subsystems of the neural processes that underlie perception.
Parvocellular Cells
Magnocellular Cells
What are parvocellular cells sensitive to?
colour, pattern and form
What are magnocellular cells sensitive to?
They give rise to motion detection and depth perception.
What cells are not colour sensitive?
Magnocellular Cells
Within the visual _____ different cells respond to specific aspects of a _____.
cortex, stimulus
Complementary analyses occur _________.
simultaneously
Why do cells carry out colour and motion analyses simultaneously?
Its more efficient and it allows for communication between analyses.
Each region of cortex (brain) is specialised in what?
Processing a specific aspect of an object
What allows us to have a rich visual experience?
Communication at all different levels of the visual cortex.
The Visual pathway has a _______ and ______ system.
what, where
What cells is the “what” system made up of?
Parvocellular
In the “what” system where is information carried to?
Its carried to the temporal cortex.
What is the “what” system involved in?
It’s involved in identifying an object
eg. WHAT an object is
The “where” system involves ______ cells.
magnocellular
In the “where” system, where is the information carried to?
The information is carried to the parietal cortex.
What does the “where” system identify?
It identifies WHERE the stimulus is located (near, far, right, left etc.)
Explain The Binding Problem of the visual pathway.
The binding problem is: how can all the information be combined from different subsystems to form one image.
What is the possible answer to the Binding Problem?
Synchronised Neural Firing
Explain how synchronised neural firing helps us combine information.
If neuron firing is in sync and at the same rate, the brain presumes it is working on the same visual object.
What do people who have visual agnosia have problems with?
They cannot recognise common objects. (everything else they are fine with).
Patient DF can draw from memory but subsequently cannot recognise the picture that she has drawn. Name this condition.
Visual Agnosia
Visual Agnosia is a specific impairment in _______ perception.
object
Damage to the _____ _____ region of the brain can cause visual agnosia.
infero-temporal
Can people with visual agnosia avoid obstacles?
yes :)
What perceptual deficit does damage to the V5 area result in?
The inability to perceive smooth movement, can only see a series of stills
Patient LM can’t easily detect meaning from facial expressions or cross the road, what do they have a specific impairment in?
Patient LM has a specific impairment in movement perception.
What is Prosopagnosia?
The inability to recognise faces.
What has identified feature detector cells?
Single Cell recording
What does the process of identifying objects begin with?
feature detection
What is the “what” pathway also known as?
The Ventral pathway
What is the “where” pathway also known as?
The Dorsal pathway
There are ____ visual pathways.
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