Task 3 - EEG and ERP Flashcards
Single-cell recording
- Allows the recording of the activity of single neuron
- Thin electrode is inserted into animals brain and when close to a neuronal membrane, measures membranes changes in activity
Multiunit recording
- Uses microelectrodes to detect action potentials from multiple neurons simultaneously.
- Signals are amplified, filtered, and analyzed to study neural activity patterns, often in response to stimuli or behavior.
What is an EEG (Electroencephalography)?
A noninvasive method that records brain activity using scalp electrodes. It measures voltage fluctuations from neural activity, producing waveforms (e.g., alpha, beta, delta, theta) that reflect different brain states, cognition, and disorders.
ERP (Event-Related Potential)
Brain responses to specific stimuli, extracted from EEG by averaging multiple trials to reduce noise.
Unlike waves (which are ongoing brain rhythms), ERPs are time-locked to an event and reflect distinct cognitive processes.
Spatial resolution of EEG
Low; it captures brain activity with high temporal resolution but poor spatial resolution due to signal distortion as electrical activity passes through the skull and scalp.
Temporal resolution of EEG
High; it detects brain activity on a millisecond scale, making it excellent for tracking rapid neural processes, unlike fMRI, which has slower temporal resolution.
Neural Source of EEG
- EEG signals primarily originate from postsynaptic potentials in large populations of pyramidal neurons, creating dipoles.
- Radial dipoles produce signals detectable by EEG, while tangential dipoles are less detectable
Signal Propagation in EEG
- Neural activity generates postsynaptic potentials in pyramidal neurons, creating small electrical fields.
- When many neurons fire synchronously, these fields sum and propagate through brain tissue, cerebrospinal fluid, skull, and scalp.
- EEG electrodes detect these voltage fluctuations
EEG Amplifiers
- Used immediately after the electrodes pick up the electrical signals from the brain.
- The signals are typically very weak (in the microvolt range), so the amplifiers increase the signal’s strength before it is sent to the recording device
Are all ERP components always present in every experiment?
No, the presence of ERP components depends on the task, stimulus type, and cognitive processes involved. Some are task-specific
ECoG
ECoG (Electrocorticography) involves placing electrodes directly on the exposed brain tissue to measure brain activity, providing higher spatial resolution than EEG
What is the difference between signal and noise in EEG?
Signal refers to the neural activity of interest, while noise refers to artifacts or unwanted electrical interference that distort the EEG signal.
What is the difference between radial and tangential dipoles?
- Radial dipoles point perpendicular to the scalp, producing signals that are easily detected by EEG.
- Tangential dipoles are oriented parallel to the scalp, producing signals that are less detectable by EEG due to their orientation.
Artifacts
Artifacts are unwanted electrical signals or distortions in EEG data caused by external factors like muscle activity, eye movements, or electrical interference, which can distort the brain signal and reduce data quality.
Types of ERP components
- Exogenous (sensory responses)
- Endogenous (cognitive processing)
- Motor-related (related to movement preperation)
Covert and overt attention
Covert attention: Focusing on something without moving eyes there
Overt attention: Shifting gaze towards stimulus
Voluntary vs. reflexive attention
Voluntary Attention: Goal-driven, involves conscious focus.
Reflexive Attention: Stimulus-driven, automatic response to sensory events
Early vs. late selection
The early selection theory suggests that attention filters out irrelevant stimuli early in the sensory processing stage, before full analysis.
The late selection theory proposes that all stimuli are processed fully, and attention comes into play later, during the response selection stage
Attention’s effect on ERPs
Modulates amplitude and latency of ERP components, reflecting enhanced processing of attended stimuli
Inhibition of return
Inhibition of return (IOR) is the phenomenon where attention is less likely to return to a previously attended location, improving search efficiency.
What is the significance of the P1 component in relation to attention?
The P1 component reflects early sensory processing, and its amplitude increases when attention is directed toward the stimulus.
What are dipoles in EEG?
Radial and tangential dipoles
- Dipoles refer to the electrical potential difference between two points in the brain
- A dipole has a positive and negative pole, and the orientation and location of dipoles is important.
- Radial dipoles are oriented perpendicularly to the scalp, while tangential dipoles are oriented parallel to the scalp.
Volume conduction
Refers to the process by which electrical signals from neural activity spread through the brain tissue, skull, and scalp, potentially distorting the localization of the original brain source in EEG measurements
P1 component
ERPs
Early visual processing (~100 ms, positive)
N1/100 component
ERPs
80-150ms - Early sensory processing
P2/200 component
Categorization, sensory processing (~150-250 ms, positive)
N2/200 component
ERPs
Conflict detection, cognitive control (~200-350 ms, negative)
N170 component
ERPs
- Occurs at ~170 ms (negative)
- Linked to face perception, strongest in occipito-temporal regions
P3/300 component
ERPs
- Occurs around 300-600 ms (positive)
- Related to attention and decision-making (often in the oddball paradigm)
- Special because it reflects conscious awareness and cognitive processing, making it useful in research on attention etc.
Oddball paradigm
A cognitive task used in EEG/ERP research where participants respond to rare, unexpected stimuli (oddballs) among frequent, repetitive stimuli.
Lateralized Readiness Potential (LRP)
- An EEG marker of motor preparation, showing brain activity before movement
- Appears before voluntary movement (hundreds of ms before action).
- Lateralized: Stronger in the opposite hemisphere of the moving hand
