What are the 2 signals of interest in EEG recordings?
Temporal - this measures amplitude (power) and latency (time after stimulus onset) & frequency (report different processes - gamma/beta)
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What is ERS and ERD
Event related synchronisation- In response to a stimulus, activity will increase either in phase or out of phase, if it is in phase= ERS, which combines the waves to create increased power - ERD will reduce overall power but is a signincreased active
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What is a spectrogram?
Colour imaging version of ERP activity - shows power change after onset = difference in amplitude over frequency - red= increase power, blue= decrease
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Outline alpha waves
8-13hz, most predominantly found in visual parietal cortex but is present all over brain = inverse of pp attention and effort - inhibits activity - the higher power of alpha= lower power/activity of other areas- when eyes close=inhibit visual= alpha
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mazahero and jenson 2010 -alpha low/high
3 neuron circuit - pyramidal- excited one giving low alpha osc, inhibited one w high gamma- found low gamma to increase strength of connection and info transfer, high alpha inhibited info transfer
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Kelly - 2006 / Zhang+Ding, 2009 - processing and alpha levels
In visual processing task, implemented low and high power alpha over cortex - high alpha= not processed, low alpha= visually processed- alpha inhibits processing
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What effects of alpha, b and g on brain processing
Alpha and beta inhibit processes- ERD= low power= high activiy, ERS = high power = low activity- Gamma is opposite
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/Mazaheri ADHD study?
ADHd found lower task performance and attentional deficits- in an attentional task found ADHD= less alpha suppression and weaker connectivity between alpha and theta= deficits in top down processing in adhd - less active brain processes
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Keehn - 2017 - autism
autism pp lack attentional and task related skills - The more symptomatic AD found less ERD than less symp- also lower response efficient - again suggests deficits in top down processing
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Mazakeri+Johnson - alpha and gamma
found alpha suppressing gamma and brain activity- acts as info gatekeeper, only letting info in when it is at trough/ low power
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How does alpha and gamma info flow
gamma- feedforward, provides input to areas, travel up hierarchy. alpha- feedback signals, opposite to gamma, flow down the hierarchy
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What frequency travels across which space?
If low space is intended- lower frequency= beta, alpha. over large space= higher frequency= gamma
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Fries - 2009 - triangle pacman
Found when pp binded parts of an object to create a object representation, gamma synchronisation increased- ERS = higher power of wave
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gamma with MZ and DZ?
Gamma frequency varies by individual and is constant for that person over time - In MZ twins= high concordance in gamma - In DZ= low concordance of gamma
Gamma and theta waves had more power when encoding remembered photos than forgotten photos - suggest gamma and theta aid memory- higher power= more encoding
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How does EEG's localisation work?
Neural positive and negative charges across the brain are recorded and comb as a unit of 'scalp potential'- source localisation is a problem- current should be taken at different points and see how neuronal pattern changes
not all brain activity can be recorded (cancels out/ too deep), poor spatial resolution, requires large ares of synchronicity (LFP)
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EEG/ MEG differences?
EEG uses much larger signal so easier to record activity, eeg worse spatial, eeg cheap and portable, Meg not affected by conduction of scalp.
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Card 2
Front
What is ERS and ERD
Back
Event related synchronisation- In response to a stimulus, activity will increase either in phase or out of phase, if it is in phase= ERS, which combines the waves to create increased power - ERD will reduce overall power but is a signincreased active
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