EEG Principles and Signal Processing

Vocabulary flashcards covering the principles of EEG, history, signal processing, artefact removal, and analysis domains.

EEG (Electroencephalography)

A method that detects neuronal activity by picking up small fluctuations in electrical activity with very good temporal resolution (within ms) but poor spatial resolution (cms).

Temporal Resolution

The precision of a measurement with respect to time; for EEG, this is within $ms$.

Spatial Resolution

The ability to pinpoint the location of brain activity; for EEG, this is poor, typically measured in $cms$.

Neutral Reference

A measurement point (like the tip of the nose or mastoids) that captures only external noise, used to isolate brain activity by subtracting the reference signal from the electrode signal.

Hans Berger

The individual who detected the first human EEG signal in $1924$ (reported in $1929$) and first described the alpha rhythm.

Alpha rhythm

A brain wave pattern characterized by a frequency of $8-13\,Hz$, typically observed when a person's eyes are closed.

Electrode gel/paste

A substance applied between the scalp and electrode to improve contact and decrease impedance, resulting in a better signal.

Amplification

The process of increasing the very small EEG signals (typically $10\,microvolts$ to $100\,microvolts$) by a factor of $1,000$ to $100,000$.

Sample Frequency

The rate at which data points are collected in EEG, typically between $256-1024\,Hz$.

Band-pass filtered

A processing step that removes low frequency fluctuations (less than $0.5-1\,Hz$) and high frequency activity (above $70\,Hz$) associated with muscle activity.

Notch-filtered

A filter used to remove external noise from power lines, typically at $50\,Hz$ or $60\,Hz$.

Artefacts

Noise that contaminates the signal from non-brain sources, including eye blinks, muscle movements, and slow drifts.

Independent Component Analysis (ICA)

A mathematical algorithm used to identify and subtract noise sources, such as eye movements, from the EEG signal.

Electrooculogram (EOG)

The measurement of electrical activity specifically related to eye movements and blinks.

Electromyogram (EMG)

The measurement of electrical activity related to muscle movement.

Electrocardiogram (ECG)

The measurement of electrical activity related to the heart.

Frequency Domain

An analysis approach focusing on oscillatory patterns and dominant frequencies, often critical for determining emotional or attentional states.

Spectrogram

A visual representation used to plot which frequencies are dominant in an EEG signal over time.

Time Domain

An analysis approach where brain waves are analyzed in relation to specific cognitive tasks or events of interest.

Averaging Method

A technique used in the time domain where multiple trials are added together to increase the signal and cancel out random noise, which is assumed to have a mean of zero.

Contrasting Method

A method of comparing brain activity during a task against a control condition to determine if the activity is reliably associated with a cognitive process.