EEG Flashcards
An ERP is the summation of…
postsynaptic potentials in pyramidal cells.
What is a postsynaptic potential?
When neurotransmitter bind to the membrane of the postsynaptic cell.
What is an electric dipole?
A separation of positive and negative charges.
Scalp electrodes measure the voltage from…
the summation of multiple dipoles.
Observed ERP waveforms reflect the sum of several independent…
latent (hidden) components.
The temporal resolution of EEG is in…
milliseconds.
What are the advantages of EEG?
High temporal resolution
Relatively cheap (compared with fMRI)
Non-invasive
ERP component is a scalp-recorded voltage change that reflects specific…
neuro-cognitive processes.
What areas of basic research can be done with ERPs?
Attention
Memory
Language
Visual cognition
What areas of clinical research can be done with ERPs?
Schizophrenia
Neurodegenerative disorders
Depression & anxiety
What is divergence of temporal resolution?
When waveforms for 2 conditions (e.g. - faces and cars) diverge.
Divergence allows us to say that the brain…
discriminates between 2 conditions at a specific time.
EEG can explain the time course and stages of _______ _______ & _______ ________.
stimulus processing, decision making
Divergence cannot tell us…
when discrimination between conditions begins.
What is sub-division of processing?
Identifying differences between ERPs at different time points.
Sub-division of processing s dependent on…
prior knowledge of what processing stages are involved in a task.
Covert monitoring can assess neural processes in people who…
may have difficulty providing a response.
Without overt behaviour in cover monitoring it can be…
difficult to interpret the results.
Why is it difficult to deconstruct an ERP waveform into its components?
- Peaks & troughs are not always a good reflection of underlying components.
- Changes in amplitude of one underlying component can appear to change the amplitude and latency of a different component in a waveform.
- Differences in peak latency do not always correspond with changes in component timing.
What methods can be used to deconstruct ERP waveforms into their underlying components?
- Principal component analysis
- Independent component analysis
Why must the results of many trials (usually in the order of 100 or more) be averaged together?
To average out random brain activity, so that just the relevant waveform to remains, called the ERP.
Why are postsynaptic potentials recorded rather than action potentials?
Because they last longer, and action potentials may cancel each other out.
What issues are there with interpreting/measuring ERPs?
- Waveforms do not reflect all neural activity .
- PSPs last many milliseconds - new mental processes are beginning as previous activations persist.
- Multiple ERP components (related to dipoles) are active simultaneously.
- Superposition problem.
- Latency jitter.
- Between-subjects variability.
What is the superposition problem?
- ERP peaks do not = ERP components.
- The observed ERP average is made up of multiple components.
- The shape and latency of underlying components is hidden.
What is latency jitter?
The timing of components is not the same on each trial.
Effects the earliest and latest onset/offset time and effects peak amplitude.
