RPSGT Electroencephalography & Signal Interpretation Flashcards

Which EEG frequency band is most prominently associated with active cognitive processing and problem-solving?

Answer: Beta (13–30 Hz)

Beta activity predominates during active mental engagement, concentration, and problem-solving tasks.

A 60-Hz artifact appearing on EEG channels is most likely caused by:

Answer: AC electrical interference

60-Hz artifact results from alternating current (AC) electrical interference from nearby equipment or poor grounding.

During N3 sleep, the EEG is characterized by:

Answer: High-amplitude slow waves occupying ≥20% of the epoch

N3 is defined by slow-wave activity (0.5–2 Hz, ≥75 µV) comprising at least 20% of the 30-second epoch.

Vertex sharp waves (V waves) in a sleep study are most characteristic of which sleep stage?

Answer: N1 sleep

Vertex sharp waves are electropositive transients maximal at the vertex and are a hallmark of N1 sleep.

A HEOG (horizontal electro-oculogram) montage detects eye movements by placing electrodes:

Answer: At the outer canthi of each eye

HEOG electrodes are placed at the outer canthi (lateral edges) of each eye to detect lateral eye movements.

Which artifact is characterized by rhythmic, high-frequency bursts on EEG channels that correlate with the pulse rate?

Answer: Pulse artifact

Pulse artifact appears as rhythmic slow waves or spikes on EEG caused by an electrode placed over a pulsating blood vessel.

In referential (monopolar) EEG recording, the reference electrode should ideally be placed at a site that is:

Answer: Electrically neutral or minimally active

A reference electrode should be electrically neutral to accurately reflect the potential of the active electrode without introducing its own signal.

POSTS (positive occipital sharp transients of sleep) are normal EEG variants seen during which stage?

Answer: N1 and N2 sleep

POSTS are normal, benign waveforms seen in N1 and N2 sleep, maximal over occipital regions, and should not be mistaken for pathology.

The international 10-20 electrode placement system derives its name from the fact that electrodes are placed at intervals of:

Answer: 10% and 20% of skull circumference distances

The 10-20 system spaces electrodes at 10% and 20% intervals of the total skull circumference measured in each plane.

A patient's EEG shows continuous, diffuse high-amplitude delta activity throughout an entire overnight study. This pattern is most consistent with:

Answer: Severe encephalopathy or deep coma

Continuous diffuse delta without normal sleep architecture cycling suggests severe cerebral dysfunction such as encephalopathy or coma.

Which filter setting in PSG is specifically used to reduce slow-moving artifacts such as sweat and movement?

Answer: Low-frequency filter (LFF) / High-pass filter

The low-frequency filter (high-pass filter) attenuates very slow frequencies, reducing sweat and movement artifacts that appear as slow undulations.

K-complexes on EEG must have a total duration of at least:

Answer: 0.5 seconds

By AASM definition, a K-complex is a well-delineated negative sharp wave followed by a positive component with total duration ≥0.5 seconds.

In a bipolar EEG derivation, if the potential at electrode A is +50 µV and at electrode B is +20 µV, the recorded deflection will be:

Answer: +30 µV deflection reflecting A minus B

Bipolar recording subtracts the second electrode from the first (A − B), yielding +30 µV; the polarity convention determines deflection direction.

Sleep spindles are generated primarily by thalamo-cortical circuits and are typically recorded at maximum amplitude over which scalp region?

Answer: Central (C3, C4)

Sleep spindles are maximal over central scalp regions because of their thalamocortical origin projecting to sensorimotor cortex.