EEG Neuroanatomy and Physiology 2

Question 1

The posterior dominant rhythm (alpha rhythm) in a normal awake adult is generated primarily by which brain structure interaction?

Accepted Answer

Thalamocortical circuits involving the thalamus and occipital cortex

Answer

The alpha rhythm arises from synchronized oscillations in thalamocortical loops, with the thalamic relay nuclei (particularly the pulvinar and lateral geniculate) pacing cortical neurons in the occipital visual cortex.

Question 2

Which cortical cell type is the primary generator of EEG signals recorded at the scalp?

Accepted Answer

Pyramidal neurons in cortical layers III and V

Answer

Pyramidal neurons are the primary generators of scalp EEG because their elongated apical dendrites are oriented perpendicular to the cortical surface, creating open electrical fields that summate and can be detected at the scalp.

Question 3

The cortical area represented by electrode T3 (T7 in modified nomenclature) overlies which brain region?

Accepted Answer

Left mid-temporal region near the Sylvian fissure

Answer

T3 (T7) is positioned over the left mid-temporal region, approximately overlying the middle temporal gyrus near the lateral sulcus (Sylvian fissure), a common area for temporal lobe epilepsy discharges.

Question 4

What minimum area of synchronously active cortex is typically required to produce a detectable signal on scalp EEG?

Accepted Answer

6 cm²

Answer

Approximately 6 cm² (some estimates range from 6-10 cm²) of synchronously active cortex is needed to generate sufficient electrical potential to be detected through the skull, meninges, and scalp by surface electrodes.

Question 5

Delta activity (0.5-4 Hz) in a normal awake adult EEG is considered abnormal because it typically indicates:

Accepted Answer

Cortical dysfunction from structural or metabolic causes

Answer

In awake adults, delta activity is abnormal and suggests cortical or subcortical dysfunction. Focal delta suggests structural lesion; generalized delta suggests diffuse encephalopathy or deep midline dysfunction.

EEG - Electroencephalography Practice Test

EEG - Electroencephalography Practice Test

EEG Neuroanatomy and Physiology 2