8.11. Electroencephalogram (EEG); sleep phenomena. Learning and memory. Flashcards

Question

IV. Mechanism of generation of field potentials 4A. Only synchronized PSPs induce detectable EEG waves -> T/F?

Answer 1

- Individual neurons produce characteristic EPSPs and IPSPs in a synchronized manner - Under these conditions, the electrical activity form these neurons is summed -> signal strong enough to be detected on the surface - Thalamus is a very important factor in this synchronization process

Answer 2

- Different neural circuit can oscillate in the same frequency range -> when we detect an EEG wave, we cannot be entirely sure which system caused it - Example: + Thalamic delta rhythm: in deep sleep + Cortical delta: surgical removal of the thalamus -> enhancement of neocortical delta activity => Thalamocortical oscillations are important in alpha rhythm

Answer 3

- Relay nuclei and the nucleus reticularis thalami are interconnected in the thalamus - These interconnections may be responsible for the oscillations, which are transmitted to the cortex - There may also be oscillations between the cortex and relay nuclei, because the cortex will send many fibers back to the thalamus

Answer 4

one set of neurons interact with another set of neurons, and the activity oscillates in these 2 populations

Answer 5

if one neuron population is activated, this activity (after a delay), will inhibit the same neuron population – inhibitory interneurons are involved => there is an activity followed by an inhibition

Answer 6

if the neurons are inhibited for a time period, they will become spontaneously activated after the inhibition disappears

Answer 7

- Normal EEG recording => spontaneous potentials - Evoked potentials => following presentation of a stimulus - ERP: event-related potentials = time-locked to some ‘’event’’ + auditory evoked potentials (AEPs): e.g. clicking sound + visual evoked potentials (VEPs): e.g. pattern-reversal checkerboard + somatosensory evoked potential (SSEPs): e.g. peripheral nerve stimulation

Answer 8

clicking sound

Answer 9

e.g. pattern-reversal checkerboard

Answer 10

peripheral nerve stimulation

Answer 11

In order to isolate and visualize these evoked potentials on EEG, the stimuli must occur several hundred times during the EEG recording and averaged so that the background noise can be subtracted and the stimuli signal can be isolated.

Answer 12

- EEG mainly detects the dipoles which are perpendicular to the skull - However, the cerebral cortex has gyri and sulci -> the pyramidal neurons in the sulci will produce field potential parallel to the surface of the skull = not well detected by EEG -> detected by MEG - This change in current flow will generate a magnetic field -> can be measured - The magnetic field is very low = need a special device to detect the magnetic field changes induced by the current -> SQUID (superconducting quantum interference device) = a very sensitive magnetometer

Answer 13

Disease states characterized by behavioral and EEG seizures. Uncontrolled excessive activity of either part or all of the CNS

Answer 14

- Partial (focal) - Generalized

Answer 15

- Partial (focal): only part of the brain shows abnormal activity +) Partial simple seizures: consciousness is retained +_ Partial complex seizures: consciousness is lost

Answer 16

Partial simple: Jacksonian march - Originates in the motor cortex - Localized contractions of contralateral muscles - Spread follows the somatotopic map of the motor cortex - People are aware of what is occurring during the seizure

Answer 17

Partial complex: psychomotor epilepsy - Originates in the limbic structures of the temporal lobe - May cause: short period of amnesia, attack of abnormal rage, sudden anxiety, discomfort/fear, incoherent speech, mumbling of trite phase

Answer 18

Generalized: large regions of the brain are involved, and consciousness is lost - Grand mal: tonic/clonic contractions of muscles on both sides of the body (maybe aura, post-seizure depression - Petit mal: brief loss of consciousness, spike and wave EEG pattern

Answer 19

Grand mal: aura, tonic/clonic seizures - Seconds – 4min - Bites or ‘’swallows’’ his tongue, cyanosis - Urination + defecation - Post-seizure depression (stupor for minutes, sleep for hours) - Triggers = ethanol, fever

Answer 20

Petit mal: absence epilepsy - 3 to 30 seconds of unconsciousness - Maybe twitch-like contractions of muscles – usually in the head region (e.g. blinking of eye) - Typically appears first during late childhood and then disappears by age 30 - Spike and dome can be recorded over most of the cerebral cortex (involved most of the thalamo-cortical activating system)

Answer 21

- We spend about one third of our life in sleep - About 6-8h/day average requirement in adults - Sleep is a basic requirement +) Possible to remain awake voluntarily for only about 3 days +) After the 4th day, disturbed psychological functions (e.g. visual/auditory hallucinations, memory lapses, impaired moral judgement) +) Sleep deprivation was used to extract confession

Answer 22

- Endogenous rhythm ≈25 hours (?) - Normally entrained by the light-dark cycle (suprachiasmatic nuclei) - Jet lag and isolation from the outside world can mess up with the sleep cycle

Answer 23

Blue light triggers melanopsin -> stimulates retino-hypothalamic tract (non-visual fibers) -> activates suprachiasmatic nuclei in HT -> INHIBITS the SYM system (-> NE is released in the pineal gland -> release of melatonin) (hormone of darkness) - Melatonin causes sleepiness - Blue light blocks the production of melatonin = not sleepy

Answer 24

Sleep is an active process: - Sleep ≠ loss of consciousness - Sleep ≠ loss of brain activity - Actively controlled mechanism - Characterized by altered responsiveness to environmental stimuli => Cortical function is not stopped, but recognized during sleep

Answer 25

A person falling asleep passes through 4 stages of slow- wave sleep, over a period of 30-45 minutes: NREM (non-rapid eye movement) sleep: (low frequency, high amplitude waves) - Stage 1: drowsy alpha waves to theta waves - Stage 2: slow theta waves with small bursts of activity known as sleep spindles (12-14Hz) and K-complexes (large, slow potentials) - Stage 3: theta waves change to low amplitude delta waves - Stage 4: delta waves (0,5 – 2Hz), deep sleep/slow wave sleep => ANS changes: ↓HR + ↓BP => In order to wake up, the person must pass through the sleep stages in reverse

Answer 26

Stage 1: drowsy alpha waves to theta waves

Answer 27

Stage 2: slow theta waves with small bursts of activity known as sleep spindles (12-14Hz) and K-complexes (large, slow potentials) => In order to wake up, the person must pass through the sleep stages in reverse

Answer 28

Stage 3: theta waves change to low amplitude delta waves

Answer 29

Stage 4: delta waves (0,5 – 2Hz), deep sleep/slow wave sleep

Answer 30

REM sleep: (high frequency, low amplitude) - EEG is desynchronized - Muscle tone is lost, but phasic contractions occur in some muscle (eye muscles) - Cause Autonomic changes - REM sleep varies with age - Difficult to arouse a person from REM sleep, but internal arousal is common

Answer 31

- Temperature regulation is lost - HR, BP and respiration changes - Most dreams occur during REM sleep (good thing muscle tone is lost) - Penile erection

Answer 32

- Newborn: spend about half of their sleep time in REM - Young adult: 20% to 25% of their sleep is REM sleep - Elderly have little REM sleep

Answer 33

- Nuclei send their axons into the cerebral cortex diffusely, others to the thalamus - These nuclei provide persistent depolarization = ensures the awake state - Lesion of the AAS -> somnolence/coma

Answer 34

- In the lateral hypothalamic area - Uses GABA and galanin to inhibit the arousal system => VLPO active in sleep - VLPO lesion => insomnia (cannot go to sleep)

Answer 35

- In the lateral hypothalamic area - Stabilizes the arousal system (awake state) - Orexin deficiency: narcolepsy

Answer 36

Awake: - Arousal system prevails - VLPO is inhibited Sleep: - VLPO prevails - Arousal system is inhibited

Answer 37

When circadian sleep drive or homeostatic need for sleep become great enough, the flip-flop circuit will suddenly give way and reverse

Answer 38

Learning is a change in the reaction to stimuli, whereas memory is the storage of what has been learned

Answer 39

Learning/memory can be implicit or explicit: - Implicit: Unconscious, automatic behavior, behaviorally expressed (much as learned reflexes), NOT verbally expressed. - Explicit: Storage of past life events, can be verbally expressed as feelings or ideas

Answer 40

Implicit: Unconscious, automatic behavior, behaviorally expressed (much as learned reflexes), NOT verbally expressed.

Answer 41

Storage of past life events, can be verbally expressed as feelings or ideas

Answer 42

1. Non-associative learning – Reflex pathways 2. Associative – (Cerebellum and Amygdala): Entails learning to respond to a previously 3. Procedural – (Striatum): Activities learned due to repeated practice 4. Priming – (Neocortex): After a clue or trigger, memory retrieval is improved.

Answer 43

Procedural – (Striatum): Activities learned due to repeated practice - Learning to play an instrument

Answer 44

Priming – (Neocortex): After a clue or trigger, memory retrieval is improved. - A perfume scent that reminds you of a person.

Answer 45

Aided by attention, motivation, and connection to previous knowledge. a. Begins in sensory area in pre-frontal part of brain.

Answer 46

Changes in synaptic transmission OR creation of new synapses.

Answer 47

- At different parts of the brain depending on short, intermediate, or long-term memory. - Temporal lobe is important in memory storage process. - With damage or removal of the temporal lobes, patients still retain their short and long-term memories but cannot store new ones. - These patients can still learn new procedural tasks such as playing a sport or instrument, even if they do not remember practicing.

Answer 48

explicit memory can be short term, intermediate or long-term. 1. Short term – necessary for only a few moments (i.e. instructions) 2. Intermediate – information that can be learned for a few days or so but then forgotten (i.e. anatomy). 3. Long term – difficult to forget (i.e. your family’s names).

Answer 49

- Persistent strengthening of synapses based on recent patterns of activity. - This produces a long-lasting increase in signal transmission between two neurons. - It is one of several phenomena underlying synaptic plasticity (ability of chemical synapses to change their strength). - Since memories are thought to be encoded by modifications of synaptic strength, LPT is widely considered one of the major cellular mechanisms that underlies learning and memory.

Answer 50

NMDA receptors

Answer 51

LTP can increase synaptic strength for hours to days, via the following mechanism: High frequency stimulation -> ↑ AMPA-R activity -> stronger depolarization -> NMDA-R activation -> ↑[Ca2+] -> CAM-Kinase-II activation -> phosphorylation of AMPA-R -> ↑AMPA-R activity (new receptors) => The synapse has been strengthened with appearance of more AMPA receptors to the postsynaptic membrane => It will respond more rapidly and more strongly to future releases of glutamate