Sleep, Memory & Cortical Organisation
Key facts on EEG rhythms, sleep architecture, and memory mechanisms from the higher-function lecture.
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Questions Covered in This Set
11 cards to master
What does a scalp EEG electrode actually record?
Summed extracellular fields from synchronous postsynaptic potentials in the apical dendrites of cortical pyramidal neurons — not action potentials.
What does EEG amplitude indicate?
Degree of synchrony, not amount of neural activity: big slow waves = many neurons firing together; low-voltage fast ('desynchronised') = independent processing.
List the four classic EEG bands with frequencies and states.
Beta >13 Hz (alert, eyes open); Alpha 8–13 Hz (relaxed, eyes closed, occipital); Theta 4–7 Hz (N1/drowsy); Delta <4 Hz (N3 slow-wave sleep).
Which structure is the pacemaker of EEG rhythms, and by what mechanism?
The thalamus — hyperpolarised thalamocortical relay neurons burst-fire via T-type Ca²⁺ channels, with thalamic reticular nucleus GABAergic neurons enforcing synchrony.
Name the ascending arousal systems that desynchronise the cortex.
Locus coeruleus (NE), raphe (5-HT), tuberomammillary nucleus (histamine), laterodorsal tegmentum (ACh), plus orexin/hypocretin from the lateral hypothalamus.
What is the lesion in narcolepsy type 1?
Autoimmune destruction of ~90% of orexin (hypocretin) neurons, causing sleep attacks and cataplexy (REM atonia intruding into wakefulness).
What are the EEG hallmarks of N2 sleep?
Sleep spindles (12–14 Hz) and K-complexes.
Why is REM sleep called 'paradoxical'?
EEG looks awake (low-voltage, mixed frequency, sawtooth waves) and metabolic rate equals or exceeds waking, yet there is near-complete skeletal muscle atonia (diaphragm and extraocular muscles spared).
Functional roles of N3 versus REM sleep?
N3: declarative memory consolidation, glymphatic clearance (incl. amyloid-β), growth hormone pulses. REM: procedural/emotional memory, synaptic pruning.
How is the suprachiasmatic nucleus entrained to light?
Via melanopsin-containing retinal ganglion cells projecting through the retinohypothalamic tract.
Why do MI and asthma attacks cluster in the early morning?
Late-night cycles are REM-rich, with erratic autonomic control — irregular breathing, blood pressure surges, and poikilothermia.
