electrophysiological recordings of brain activity Flashcards
what are 2 electrophysiological recordings techniques?
micro-electrode recordings: measures post-synaptic and action potentials
- highly invasive
- high temporal and spatial resolution
EEG/ERP: measures post-synaptic potentials
- non-invasive
- high temporal but low spatial resolution (can’t localise activity)
what are 2 metabolic recording techniques?
PET: measures indirect metabolic correlates of neural activity
- sort of invasive
- high spatial but low temporal
fMRI: measures indirect metabolic correlates of neural activity
- non-invasive
- high spatial but low temporal
describe micro-electrode recording?
what they measure?
how they measure?
strengths and weakness?
very thin electrodes inserted into brain tissue to measure electrical activity
measures ‘single-cell recordings’ (one neuron) and the firing rate of neurons (frequency of action potential generated)
only performed during surgery as highly invasive e.g brain
high temporal and spatial resolution and most direct & precise measure of brain activity
what did Quiroga and colleagues find?
many cells in the medial temporal lobe showed selective responses to a specific item (irrespective of size, view etc.)
also responded to the name of the person and famous buildings
describe EEG?
what sensitive and not sensitive to?
strengths and weakness?
- measure the summation of multiple local field potentials (LFPs) on the scalp which is presented as a voltage
- sensitive to activity in cortical tissue not so much further down in the scalp
- not sensitive to action potentials (spikes)
high temporal but low spatial resolution
non invasive
what are the 3 ways of analysing EEG data?
- how frequently singal oscillated in a certain amount of time (frequency)
- shape or frequency can inform on sleep pathways or pathologies e.g epilepsy
- segments can be analysed separately (ERPs)
what happens if you missed a night of sleep?
wouldn’t catch up on all the hours of sleep missed but catch up on all REM sleep missed (can detect this through the frequencies of EEG)
how can EEG be used to detect conscious awareness?
what has one study found about those in a vegetative state?
- high frequency of EEG activity associated with greater cortical actvitiy
- recorded high frequency over mortor cortex to assess conscious awareness of those in vegetative state
Cruse et al. found 3/16 activated the correct motor areas instructed suggesting presence of conscious awareness in these patients
what is a vegetative state?
no overt motor or verbal responses
no voluntary behaviour from upper and lower limbs
how can an EEG be used to measure epilepsy?
large amplitude discharges (due to excessive synchronisation of post-synaptic potentials) in those with epilepsy
discharges can be observed during seizures (ictal activity) or between seizures by EEG (inter-ictal activity)
describe ERPs?
method of analysing EEG recordings by extracting from the EEG segments time-locked to specific events (stimuli or responses)
how do you average segments of EEGs?
mean of reactions to stimulus over a multitude of trials
separate stimulus are separately averaged
how are ERP waves analysed?
- order - which number peak
- latency - timing after stimulus onset
- polarity - positive or negative
what is the relationship of N400 amplitude and semantics of a sentence?
amplitude is proportional to the predictability of the word in a sentence (semantics and congruency - how well word fits in sentence)
spikes negative when less predictable
what is a psychological refractory period? (PRP)
when presenting 2 tasks in rapid succession:
the period of time in which response to second task is affected by the 1st task still being processed
