EEG Neuroanatomy and Physiology 4 — Questions and Answers
Question 1: Which cortical layer contains the large pyramidal neurons (Betz cells) that give rise to corticospinal tract fibers?
- Layer II
- Layer IV
- Layer V (Correct answer)
- Layer VI
Correct answer: Layer V
Layer V (internal pyramidal layer) contains Betz cells, the large pyramidal neurons projecting to the spinal cord via the corticospinal tract.
Question 2: The thalamocortical relay neurons that synchronize cortical oscillations and contribute to sleep spindles are located in which thalamic nucleus?
- Pulvinar
- Reticular nucleus (Correct answer)
- Ventral posterolateral nucleus
- Mediodorsal nucleus
Correct answer: Reticular nucleus
The thalamic reticular nucleus (TRN) GABAergic neurons pace sleep spindles by rhythmically inhibiting thalamocortical relay neurons.
Question 3: What property of pyramidal neurons makes them the primary generators of scalp-recorded EEG signals rather than stellate cells?
- Higher firing rates
- Open-field geometry with parallel dendrites perpendicular to cortical surface (Correct answer)
- Greater absolute membrane potential
- Larger action potential amplitude
Correct answer: Open-field geometry with parallel dendrites perpendicular to cortical surface
Pyramidal neurons are arranged in parallel columns perpendicular to the cortical surface, creating open-field dipoles whose extracellular currents summate and propagate to the scalp.
Question 4: During an EEG-recorded absence seizure, the 3 Hz spike-and-wave discharge is generated by abnormal oscillations between the cortex and which structure?
- Hippocampus
- Basal ganglia
- Thalamus (Correct answer)
- Cerebellum
Correct answer: Thalamus
Absence seizures arise from abnormal thalamocortical resonance, with cortical and thalamic circuits entraining at ~3 Hz spike-and-wave frequency.
Question 5: The lateral sulcus (Sylvian fissure) separates the frontal and parietal lobes above from which lobe below?
- Occipital lobe
- Temporal lobe (Correct answer)
- Insular lobe
- Limbic lobe
Correct answer: Temporal lobe
The lateral sulcus separates the frontal and parietal lobes superiorly from the temporal lobe inferiorly.
Question 6: Which neurotransmitter released by basal forebrain neurons desynchronizes the EEG and promotes wakefulness by depolarizing cortical neurons?
- GABA
- Serotonin
- Acetylcholine (Correct answer)
- Glycine
Correct answer: Acetylcholine
Basal forebrain cholinergic neurons release acetylcholine onto cortical neurons, causing depolarization and EEG desynchronization characteristic of wakefulness and REM sleep.
Question 7: The primary somatosensory cortex, which generates somatosensory evoked potentials recorded by EEG, is located in which gyrus?
- Precentral gyrus
- Postcentral gyrus (Correct answer)
- Superior temporal gyrus
- Angular gyrus
Correct answer: Postcentral gyrus
The postcentral gyrus (Brodmann areas 1, 2, 3) constitutes primary somatosensory cortex and is the main generator of early cortical SEP components.
EEG Neuroanatomy and Physiology 4
Which cortical layer contains the large pyramidal neurons (Betz cells) that give rise to corticospinal tract fibers?