EEG and Symmetry Flashcards
Who invented EEG and when?
Hans Berger in 1929
What is current?
the flow of charged particles
represented by symbol I
What is voltage?
the potential for current to flow from one place to another
represented by symbol V
What does EEG measure?
measures voltage between active electrode and a reference electrode
What is the temporal resolution like in an EEG?
good
What is the spatial resolution like in an EEG?
poor
What is an event related potential (Luck, 2005)?
the signal you get from an EEG
electrophysiological markers of a discrete cognitive or perceptual event in the brain
What does error related negativity mean?
happens on trials which have made an error
Who made claims on the extrastriate cortex and symmetry?
Sasaki et al (2005)
What is the network involved in symmetry?
a network of symmetry sensitive brain areas in extrastriate cortex
What area is not sensitive to symmetry?
the striate cortex (V1)
only areas higher in visual hierarchy are sensitive to symmetry (extrastriate cortex)
What does the network in the extrastriate cortex do in symmetry?
the network responds to symmetry automatically, even when people aren’t attending to it
sometimes can go beyond this and recover symmetry in an object
What does the network generate?
the Sustained Posterior Negativity (SPN)
What is the SPN?
an event related potential (ERP) that measures brain response to symmetry
What does the network respond to?
symmetry and anti-symmetry
What is the symmetry network indifferent to?
colour
could paint a symmetrical image in different colours but response is always the same
What does perceptual goodness mean?
the perceptual strength or salience of a configuration
W-load is a measure of perceptual goodness that varies from 0 to 1
Makin et al (2015), symmetry responses are…
symmetry responses are view invariant when people attend to symmetry
What does view invariance mean?
the ability of humans to easily recognise objects when seen from different viewpoints
meaning ppts can spot symmetry even from diff angles
How does the network code symmetry in each hemisphere?
the network canoed symmetry independently in each hemisphere
due to the brain having a crossover design
What is the contralateral SPN?
in the back of the head and on the opposite side to the where the symmetry is shown
it’s the same whether people attend other symmetry or random
What does fMRI tell us?
which brain areas respond to symmetry and generate SPN
How can symmetry response increase?
through repeated presentation
(SPN priming)
What is meant by habituation?
decrease in a person’s response to stimuli after repeated exposure
What is meant by priming?
exposure to one stimulus influences how someone perceives a subsequent stimulus
How can you learn a lot from symmetry perception?
by pooling data from all experiments into a big catalogue
When is symmetry processing enhanced?
during active regularity discrimination tasks
Is the brain’s response to symmetry left lateralised or right lateralised?
right lateralised
What blocks symmetry processing?
seeing negative superimposed words
What can activate the extrastriate symmetry network?
hallucinogenic drugs
