Seminar 2 - Electrophysiology Methods Flashcards
Electrophysiology methods - brain electrophysiology
The recording of:
1. Single cell electrical activity
2. Electroencephalography (EEG)
- event related potentials (ERPs)
- oscillations
3. Magnetoencephalography (MEG)
- event related magnetic fields (ERFs)
- oscillations
4. Electrocorticography
And other measures of electric and magnetic brain activity
Single cell recording
Relatively uncommon method for studying humans
Relevant for research with animals
EEG
Uses electrical activity from the scalp
- uses electrodes
- gives a reading in wave patterns
Challenges
Conductivity of skull between 1/40 and 1/80 of the conductivity of the brain
We are only picking up a tinny fraction of actual brain activity
WWG wave types
Active
Relaxed
Sleepy
(These are relative to the study of cognition)
Sleep
Deep sleep
Coma
Frequency bands and underlying assumptions
> 30 Hz - gamma - problem solving, concentration
13-30 Hz - beta - busy, active mind
8-13 Hz - alpha - reflective, restful
4-8 HZ - theta - drowsiness
(Relative for the study of cognition)
0.3-4 Hz - delta - sleep, dreaming
Sensory-motor-rhythm (SMR aka micro rhythm)
SMR 13-15 Hz
Sensory-motor-rhythm, the individual and specific frequency band in which the sensory and motor cortex communicate to facilitate efficient interaction with the world (unique frequency band to red cue interfering noise)
Electrophysiological measures from other body parts
Electrophysiological measures not only only informative tho thr study of cognition when measuring from the brain/scalp
Other measures can help us make inferences about cognitive and emotional states
- heart rate - changes in heart rate tell us about arousal, stress or emotional states
- respiratory rate - changes tell us about arousal, stress or emotional states
- electro-cardiogram - 1 ECG = 1 heart rate
- EMG
Electromyography (EMG)
Measures muscle response
EMG can sense isometric muscular activity where no movement is produced
Reveals nerve or muscle dysfunction, or problems with nerve-to-nerve muscle signal transmission
EMG detects invisible neuromuscular activity (e.g. hidden frowning or smiling) and can be used to detect emotions in psychological experiments because even if we don’t move our face, the frowning and smiling muscles get impulses when we experience emotions
EMG facilitates the use of subtle motionless gestures to control inferences without being emotive and without disrupting the surrounding environment
These signals can be used to control a prosthesis to as a control signal for electronic devices (human-machine interaction) e.g. for people who can’t speak
Electrodermal activity (EDA, in older papers also called galvanic skin response)
EDA refers the the variation of the electrical conductance of the skin in response to sweat secretion
EDA biofeedback measures the electrical characteristics of the skin using methods such as skin conductance response (SCR) snd skin conductance level (SCL)
Measures: stress, arousal, emotion, cognitive load
Event related potentials (ERPs)
Stimulus onset:
Event to which we relates the electric potentials that we are measuring
ERPs are categorised by:
- polarity (neg vs pos)
- latency (how long after onset)
- amplitude (in microV)
- topographic distribution (maps)
Labelling conventions:
- descriptive labelling: P300, N400, N280, P1, N1
- functionality labelling: mismatch negativity (MMN), error relates negativity (ERN)
ERP effects vs components
An ERP effect is a modulation (mostly split due or latency) of a particular ERP component or just the differences between two conditions in the ERP waveform
Example: N400 vs N400 effect
ERPs vs Reaction time
Multidimensional nature of the signal
- we can measure electrical signals from the scalp while people can engage with stimuli over time and we can simultaneously also observe behaviour
Continuous nature of the signal
- task ones not need interruptions (e.g. trial and trial) that interfere with natural behaviour
No addition task requirements
- we can just observe activity without expecting behaviour (e.g. watch movies or listen to music)
- in fact, we don’t deign an experiment at allo
Open bran EEG (also called ECoG)
= recording electro-encephalographic signals directly from the surgically exposed cerebral cortex
Often used simultaneously with cognitive testing
Promising technique as implants for use of brain-computer interfaces (direct neural interferences that provide control of prosthetic, electronic or communication devices via direct use of individual’s brain signals)
Magneto-encephalo-graphy (MEG)
A functional neuroimaging technique for mapping brain activity by recording magnetic fields (a little Bit like fMRI in that we can locate source of signal better but still and electrophysiological technique)
