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Toolkit 2
What is brain electrophysiology?
The study of brain activity by placing electrodes on the head to measure waves of brain activity and neurons firing.
What does single cell electrical activity measure?
The electrical activity of individual neurons.
What is Electroencephalography (EEG)?
A method to record electrical activity of the brain using electrodes placed on the scalp.
What are event related brain potentials (ERPs)?
Brain responses that are the direct result of a specific sensory, cognitive, or motor event.
What are oscillations in EEG?
Rhythmic patterns of electrical activity in the brain.
What is Magnetoencephalography (MEG)?
A technique for measuring the magnetic fields produced by neural activity in the brain.
What are event related magnetic fields (ERFs)?
Magnetic responses in the brain that are time-locked to specific events.
What are oscillations in MEG?
Rhythmic patterns of magnetic activity in the brain.
What is the main difference between EEG and MEG?
EEG measures electrical activity, while MEG measures magnetic field changes.
What is Electrocorticography?
EEG recordings taken directly from the brain during open brain surgery.
What does Electrocorticography measure?
Direct electrical activity from the brain.
What is microscopic scales of neuron representation?
the representation of the activity of one specific neuron
What is mesoscopic scales of neuron representation?
measures local networks - talking about 8000 neurons firing together
What is macroscopic scales of neuron representation?
talking about 100,000 to millions of neuron firing at the same time large networks that give of the same neural activity we can measure
What is single cell recording?
A method for studying the activity of individual neurons.
Is single cell recording a common method for studying humans?
No, it is relatively uncommon.
Which animals are relevant for research using single cell recording?
Rodents, primates, and sometimes cats and dogs.
Why is single cell used in humans regarding peripheral nerves?
To figure out the extent to which we can save or recycle the limb or neural function in an injured or paralysed person.
What role do muscles play in assessing nerve function?
Muscles provide neural activity to see to which extent we can still use that nerve.
EEG
most common type Measures electrical activity from the scalp
What is the conductivity of the skull compared to the brain?
The conductivity of the skull is between 1/40 and 1/80 of the conductivity of the brain.
What fraction of actual brain activity does EEG pick up?
EEG picks up only a tiny fraction of actual brain activity.
What types of tissue affect electrical activity and conductivity in EEG?
Lots of cool liquid slime tissue etc. have different levels of electrical activity and conductivity.
What conditions must be met for EEG to measure brain activity?
EEG can only measure open fields if the synapse is closed and there are no open dendrites.
What EEG wave types are relevant for the study of cognition?
active, relaxed, sleepy
What are the features of a coma wave length?
few slope changes per second or hertz
depending how active a person is they have changed in wave length
What is the characteristic of the alpha frequency band?
Alpha is not very fast.
What mental states are associated with beta and gamma frequency bands?
Beta and gamma are associated with high focus and attention.
Which areas of the brain are involved in beta and gamma frequency bands?
They are produced by areas of the brain involved in deeper thought.
What does SMR stand for in the context of frequency bands?
SMR stands for Sensory Motor Rhythm.
What is the function of SMR?
SMR enables fast communication between performing actions and perceiving the environment.
Which frequency band is exclusively used by the primary motor cortex and sensory cortex?
SMR is exclusively used by the primary motor cortex and sensory cortex.
How does SMR contribute to survival?
SMR helps us survive by enabling fast responses without distractions.
What is the frequency range of Sensory-Motor Rhythm (SMR)?
13-15 Hz
What does Sensory-Motor Rhythm (SMR) facilitate?
Efficient interaction between the sensory and motor cortex.
What is the purpose of the unique frequency band of Sensory-Motor Rhythm (SMR)?
To reduce interfering noise.
What do electrophysiological measures from the brain/scalp inform us about?
They inform us about cognition.
What do electrophysiological measures from other parts of the body provide insights about?
they can help make inferences about cognitive and emotional states.
Why is it important to measure heart rate in EEG recording?
To subtract it from the brain signals and clean the data as it bleeds across into other areas.
What can heart rate indicate in an EEG recording?
It can indicate how stressed a person is.
What does respiration measurement indicate in an EEG recording?
It can also indicate how stressed a person is.
What does EMG from the jaw indicate in relation to stress?
Jaw clenching may be related to stress and could be meaningful.
Why might you want to remove EMG signals from the jaw in EEG recordings?
Because they may interfere with the interpretation of brain signals.
What does electromyography (EMG) measure?
Muscle response.
What is readiness potential in EMG?
It measures impulses in muscles when they are ready to fire.
How does EMG relate to fight or flight response?
It explains that when in fight mode, it is easier to punch someone.
What type of muscular activity can EMG sense?
Isometric muscular activity where no movement is produced.
What can EMG reveal about muscle and nerve function?
It reveals nerve or muscle dysfunction, or problems with nerve-to-muscle signal transmission.
What type of neuromuscular activity can EMG detect?
Invisible neuromuscular activity, such as hidden frowning or smiling.
How can EMG be used in psychological experiments?
To detect emotions, as muscle impulses occur even without visible movement.
What is one application of EMG in human-machine interaction?
To control interfaces using subtle motionless gestures.
How can EMG assist individuals who cannot speak?
It can be used to control prosthetics or as a control signal for electronic devices.
Why is EMG considered useful for measuring emotional states?
It provides an objective way to measure emotions, which people may not be honest about.
What does EDA stand for?
Electrodermal activity
What is electrodermal activity (EDA)?
EDA refers to the variation of the electrical conductance of the skin in response to sweat secretion.
What methods are used to measure EDA?
Skin conductance response (SCR) and skin conductance level (SCL).
What physiological measures can EDA assess?
Stress, arousal, emotion, and cognitive load.
What is a common application of EDA?
Used for lie detectors.
What physiological response is linked to lying?
Increased sweating and high blood pressure, indicating stress.
What is the main problem when measuring electrical signals from the human body?
Amplification is the main problem, as environmental signals are larger than those produced by the body.
What must be done to isolate the signals of interest from noise in electrical measurements?
You must signal out what you are interested in and isolate it from the noise.
What is the most important method to clean up noise in signal measurement?
Enhancement or averaging by performing the task hundreds of times and taking the average.
Why does averaging help in cleaning noise from electrical signals?
Environmental noise and physical noise will not be synchronized, so averaging removes them.
Stimulus Onset
Event to which we relate the electric potentials that we are measuring
ERPS are categorised by:
Polarity (neg vs pos)
Latency (how long after onset?)
Amplitude (in μV)
Define Topographic distribution
Topographic EEG analysis includes different techniques to display the spatial distribution of brain electrical activity.
Labelling conventions for ERPs
Descriptive labeling: P300, N400, N280, P1, N1
Functional labeling: Mismatch Negativity (MMN)
What is the N400?
-Negative wave, peaking at 400ms
-Generated when subjects attend to and process words
-Related to semantic processing
What is an ERP effect?
An ERP effect is a modulation (mostly in amplitude or latency) of a particular ERP component, or the difference between two conditions in the ERP waveform.
What does the N400 effect reflect?
The N400 effect reflects the predictability of a word to be processed.
Why is the N400 effect smaller for the word 'eat'?
The N400 effect is smaller for 'eat' because it is preactivated.
Why is the N400 effect larger for the word 'cry'?
The N400 effect is larger for 'cry' because it is not preactivated.
What is the multidimensional nature of the signal in ERPs?
We can measure electric signals from the scalp while people engage with stimuli over time and simultaneously observe behavior.
What is the continuous nature of the signal in ERPs?
The task does not need interruptions that interfere with natural behavior.
What are the additional task requirements in ERP studies?
We can observe activity without expecting behavior, such as watching movies or listening to music.
Do ERP studies require experimental design?
No, we do not need to design an experiment at all.
Higher error rates
occur for something something unexpected
What is a more specialized type of electrophysiological measure?
Open brain EEG (also called ECoG)
What does open brain EEG measure?
Electro-encephalographic signals directly from the surgically exposed cerebral cortex.
How is open brain EEG often used?
Simultaneously with cognitive testing.
What is a promising application of open brain EEG?
Implants for brain-computer interfaces that provide control of prosthetic, electronic, or communication devices via direct use of brain signals.
How does open brain EEG differ from other techniques?
It can measure signals directly from the brain, unlike other techniques that show only a fraction of signals.
What is a significant challenge of using open brain EEG?
Open brain surgery takes hours.
What is a key advantage of open brain EEG?
It allows testing of neurons firing without much noise.
What is Ecog?
Ecog stands for electrocorticography, a technique that involves placing a silicon sheet on top of the cortex.
How does Ecog work?
Ecog works by using silicon channels attached to electrodes to measure electrical activity in the brain.
What medical purposes does Ecog serve?
Ecog is used to identify dysfunctional tissue, such as tumors that are not firing.
Why is Ecog useful in medical procedures?
Ecog helps identify critical functions in tissue, such as language, that doctors want to preserve to maintain quality of life.
How can Ecog assist individuals who cannot communicate naturally?
Ecog can enable communication with a computer, allowing individuals to display their thoughts and steer mobility aids.
Is Ecog becoming more popular?
Yes, Ecog is becoming more popular in both medical and research settings.
What does MEG stand for?
Magneto-Encephalo-Graphy
What is the primary purpose of Magneto-Encephalo-Graphy (MEG)?
To map brain activity by recording magnetic fields.
How does MEG compare to fMRI?
MEG can locate the source of signals better than fMRI.
What type of technique is MEG?
An electrophysiological technique.
What is a key advantage of MEG?
It provides direct observation of electrical activity in the brain with better spatial resolution.
What does EEG measure?
EEG measures electric waves.
How is EEG positioned on the head?
EEG lies flat on the skull and uses conductive gel.
What does MEG measure?
MEG measures magnetic fields produced by electrical currents.
How is MEG different from EEG in terms of sensor size?
MEG sensors are much bigger and positioned further away from the head.
What is a key advantage of MEG over EEG?
MEG can detect inconsistencies in the electromagnetic field over a larger area, providing better directionality.
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