Sleep Waveforms and PSG Scoring Vocabulary

This set of vocabulary flashcards covers essential EEG waveforms, measurement criteria, and eye movement patterns used in sleep study scoring as per the AASM manual.

Amplitude

The amount of voltage that is measured in a waveform, calculated by subtracting the peak value from the lowest value.

Frequency

The speed that the voltage goes up and down, measured in waves per second or hertz ($Hz$).

Zero Crossing

A method to measure duration beginning when a waveform reaches $0$ microvolts, encompassing the negative and positive half waves until it returns to the zero line.

Alpha Rhythm

EEG rhythms between $8$ and $13$ hertz that are most prominent when a patient is awake, relaxed, and has their eyes closed, typically with an occipital distribution.

Sinusoidal

A waveform description meaning smooth and regular, often used to describe alpha rhythm and sleep spindles.

Attenuation

The decrease in amplitude or disappearance of the alpha rhythm when a patient opens their eyes.

Dominant Posterior Rhythm

The background rhythm slower than $8$ hertz found in children under age three.

Low Amplitude Mixed Frequency (LAMF)

EEG activity generally below $20$ microvolts with a frequency mostly between $4$ and $7$ hertz, appearing during sleep onset (stage N1) and REM sleep.

Vertex Sharp Waves

Sharp waveforms occurring during stage N1 sleep with a duration of less than $0.5$ seconds ($2$ hertz or higher) that are highest in the central (CZ) channel.

K complexes

Hallmark waveforms of stage N2 sleep with a frequency of less than $2$ hertz (duration greater than $0.5$ seconds), characterized by an initial negative peak followed by a slower positive component.

Sleep Spindles

Isolated bursts of activity between $11$ and $16$ hertz (most commonly $12$ to $14$ hertz) lasting at least $0.5$ seconds, which are key markers of stage N2 sleep.

Slow Waves

Waveforms characteristic of stage N3 sleep with a frequency between $0.5$ and $2$ hertz and a minimum peak-to-peak amplitude of $75$ microvolts.

Sawtooth Waves

Waveforms in the central channel with a $2$ to $6$ hertz frequency range that resemble the teeth of a hand saw and are strongly supportive of stage R sleep.

Bio-cals (Biological Calibrations)

A series of intentional physiological movements (like blinking or looking left/right) performed to verify that PSG channels are recording accurately.

Outer Canthus

The corner of the eye where the eyelids meet, used as the placement site for eye movement (EOG) electrodes.

Bell's Phenomenon

A reflex upward rotation of the eye occurring during blinking or eye closure.

Reading Eye Movements

A distinctive pattern reflecting scanning across a line of text followed by a sharp movement back to the start of the next line.

Slow Eye Movements (SEMs)

Eye movements where the initial portion lasts more than $0.5$ seconds, often seen during the transition to sleep and stage N1.

Rapid Eye Movements (REMs)

Eye movements with a sharp initial component occurring in bursts, used to score stage R sleep.

Muscle Atonia

The state of lowest muscle tone during the night, typically occurring during stage R sleep.

Muscle Twitches

Brief increases in chin EMG activity lasting less than $0.25$ seconds, often seen during stage R sleep concurrently with rapid eye movements.