EEG and MEG / ERP's ARTICLES Flashcards
EEG and MEG: Relevance to Neuroscience & A brief introduction to the use of event-related potentials in studies of perception and attention
What is the primary advantage of ERPs over modern neuroimaging techniques?
The primary advantage of ERPs is their high temporal resolution, allowing measurement of brain activity on a millisecond scale.
What fundamental brain activity does ERP measure?
ERPs measure postsynaptic activity of neural ensembles rather than individual neuron action potentials.
Which ERP component is associated with preparatory cognitive activity?
The Contingent Negative Variation (CNV).
Why is the 10/20 electrode placement system important in ERP studies?
It standardizes electrode placement, making ERP findings easier to integrate and replicate across studies.
What are the C1, P1, and N1 components responsible for?
These components reflect the early stages of sensory and perceptual processing in the brain.
Define the term ‘inverse problem’ in the context of ERP analysis.
The inverse problem refers to the difficulty of localizing neural generators of ERP effects from scalp recordings due to multiple possible solutions.
What does the N2pc component indicate?
It is associated with the deployment of covert attention to visual field targets.
Name two methods to improve the signal-to-noise ratio in ERP studies.
Collecting a large number of trials and ensuring a noise-free recording environment.
How are ocular artifacts, such as eye blinks, addressed in ERP studies?
By using electrooculogram (EOG) recordings or excluding trials contaminated by artifacts.
What is baseline correction, and why is it used?
Baseline correction involves subtracting the average prestimulus voltage from the entire waveform to isolate stimulus-related effects.
Why do ERP researchers often use randomization in trial presentation?
To minimize anticipatory effects and ensure accurate stimulus-related waveform measurements.
What is the P3 component known to reflect?
Working memory updating and categorization processes.
What can cause distortions in ERP amplitude and timing?
Aggressive filtering during data processing.
Why is it essential to use a sufficient number of artifact-free trials in ERP experiments?
To ensure reliable measurements of ERP components like C1, P1, and N1.
What role does the alpha band play in ERP recordings?
Alpha activity is a major source of noise overlapping with early ERP components.
What are the ERN and Pe components associated with?
Error processing and evaluation following a behavioral response.
Why is the spatial resolution of ERP recordings limited?
The layers of tissue between the brain and the scalp distort the electrical signals.
How do ERPs contribute to understanding cognitive processing?
They allow visualization of brain activity as it unfolds over time, from sensory input to behavioral response.
What distinguishes stimulus-locked ERP waveforms?
They are time-locked to the presentation of a stimulus, reflecting sensory and cognitive processing.
What is the role of the CNV in motor preparation?
It reflects the buildup of activity in anticipation of an expected stimulus.
What do EEG and MEG primarily measure in the brain?
EEG measures electrical fields, while MEG records magnetic fields generated by neuronal activity.
What is a major difference between EEG and MEG in terms of sensitivity to neural sources?
EEG is sensitive to both radial and tangential sources, whereas MEG primarily detects tangential components.
What condition must neurons meet to generate detectable EEG/MEG signals?
Neurons must be active synchronously and spatially organized to form a functional entity.
What is the ‘forward problem’ in EEG/MEG studies?
Calculating scalp electric or magnetic fields from known neuronal sources.
What is the ‘inverse problem,’ and why is it challenging?
Estimating neuronal sources from scalp recordings; it has multiple solutions without specific constraints.
How do EEG and MEG signals differ in terms of spatial distortion?
MEG signals experience less spatial distortion than EEG due to the properties of surrounding tissues.
What role do neuronal oscillations play in cognitive processes?
They facilitate information coding, modulate attention, and enable communication between neuronal populations.
Name the primary EEG/MEG frequency bands and their general functional associations.
Delta (<4 Hz): Deep sleep and unconscious processes.
Theta (4-8 Hz): Memory and navigation.
Alpha (8-13 Hz): Relaxation and inhibition of irrelevant stimuli.
Beta (14-30 Hz): Active thinking and motor planning.
Gamma (>30 Hz): Perception and consciousness.
What is ‘phase-locking value’ (PLV) used for in EEG/MEG studies?
To measure functional connectivity between brain regions by analyzing the consistency of phase relationships.
What is the significance of gamma oscillations in perception?
They play a key role in forming neural representations and supporting the binding of sensory information into coherent perceptions.
How can neuronal synchrony be achieved according to EEG/MEG studies?
Through oscillations that align neuronal activity, facilitating effective communication and coordination.
What is Independent Component Analysis (ICA), and how is it used in EEG/MEG?
A preprocessing method to separate EEG/MEG signals into statistically independent components, often used for artifact removal.
Why are EEG/MEG signals more distorted when passing through the skull?
The skull and other tissues have varying electrical resistivities that affect the signal.
What is ‘functional connectivity’ in the context of EEG/MEG?
The statistical association between activities of different brain regions, as inferred from signals.
What is ‘effective connectivity’?
The causal influence one brain region exerts over another.
How do EEG/MEG oscillations differ in spatial extent across frequency bands?
Lower frequencies (e.g., delta) engage broader spatial domains, while higher frequencies (e.g., gamma) are more localized.
What is the role of cross-frequency coupling in cognitive processing?
It integrates information across different oscillatory frequencies, such as gamma modulated by theta rhythms.
What distinguishes induced from evoked EEG/MEG activities?
Induced activities are not precisely time-locked to an event, whereas evoked activities are.
How are EEG and MEG used together with fMRI in neuroscience?
To combine the temporal resolution of EEG/MEG with the spatial resolution of fMRI for a comprehensive view of brain activity.
What is the ‘binding hypothesis’ associated with gamma oscillations?
It suggests that synchronization in the gamma band integrates neural assemblies to form unified percepts or actions.
