Neurobiology of Memory

Question 1

what is the neurobiology of memory

Answer 1

neural function depends on connections; altering connections alters function. If these changes derive from previous activity, and persist, they are memory. Memory is implemented as synaptic plasticity: changes in connections and connection strength.

Question 2

What is Hebbian plasticity?

Answer 2

1948 connections recorded experience, therefore there must be rules for changing connection strength. For example, if the firing of neuron A generally precedes the firing of neuron C, C should “pay attention” to A’s activity by making that connection stronger. Conversely if B’s firing has little relationship to C’s, C should ignore B to perform more efficicently, by weakening the synapse between them. Such plasticity rules are catchphrased “neurons that fire together, wire together’’

Question 3

Explain Working Memory

Answer 3

Sustained mental representations, focus on a task (attention)
Prefrontal cortex: controlling other cortical regions

Question 4

What is Short term memory & from which part of the brain is it associated?

Answer 4

Short term memory Orientation, events of the day, sequence of activity

Hippocampus: forming associations, across cortical activity

Question 5

What is Episodic memory and from which part of the brain is it associated?

Answer 5

Episodic memory
Long term recollection of specific events and times
Temporal lobe: associating other cortical regions

Question 6

What is somantic memory and from which part of the brain is it associated?

Answer 6

Semantic Memory Knowledge of the world, not related to specific times (facts) Connectional structure of the whole cortex

Question 7

What is motor sequencing and from which part of the brain is it associated?

Answer 7

Motor Sequencing
Learned patterns of movement enabling smooth muscle execution (“muscle memory”, misleading)
Striatum, cerebellum and premotor cortex

Question 8

What’s emotional learning?

Answer 8

Emotional learning Emotional responses associated with events/people/situations Amygdala, cingulate, hippocampus, reward systems

Question 9

What does the hippocampus in relation to memory do?

Answer 9

forms temporary index of the days events

Question 10

what does the amygdala do in relation to learning?

Answer 10

stress and novelty of situations

Question 11

what does the temporal lobe do do in relation to learning?

Answer 11

Longer term indexing of associations

Question 12

Where do you find working /attention

Answer 12

Working memory activity is visible in frontal, parietal and Wernicke‘s area while a subject holds a series of letters in working memory.

Question 13

explains what happens during the day in terms of memory

Answer 13

During the day we “make notes” in short term memory. The hippocampus makes temporary linkages between cotical representations. Long term memory requires linkages to endure, requiring alteration to the cortex. Cortical linkages can become lasting associations (persisting years and decades)

Question 14

How do these short term memories get made into long term memories

Answer 14

Short term associations become long-lasting memories if they are relevant. For emotional events, the amygdala and cingulate signal importance/salience. Learning experiences (failures of prediction) require an update of the cortex’s “model” of the outside world.

Question 15

What is sleep?

Answer 15

Daily loss of consciousness.
Reversible state of perceptual disengagement/ unresponsiveness to environment.
Complex amalgam of physiological and behavioural processes

Question 16

In an EEG rhythm, what would you see when a person is awake?

Answer 16

beta waves

Question 17

In an EEG rhythm, what would you see when a person is drowsy?

Answer 17

alpha waves

Question 18

In an EEG rhythm, what would you see when a person is in NREM 1?

Answer 18

thelta waves

Question 19

In an EEG rhythm, what would you see when a person is in NREM 2?

Answer 19

theta waves, spindles and potassium complexes

Question 20

In an EEG rhythm, what would you see when a person is in NREM 2-4

Answer 20

delta waves, increasing

Question 21

In an EEG rhythm, what would you see when a person is in REM

Answer 21

Saw tooth waves, beta

Question 22

Alpha Activity -
what is the frequency?
what is the amplitude
what does it indicate?

Answer 22

frequency: 8-13 hertz
Amplitude shifts up and down
indicates transient relaxation during waking

Question 23

Theta Activity -
what is the frequency?
what is the amplitude
what does it indicate?

Answer 23

Lower frequency: 3-7 hertz
Most prominent in the central cortex
THE MOST COMMON FREQUENCY OBSERVED DURING SLEEP

Question 24

Delta Activity
what is the frequency?
what is the amplitude
what does it indicate?

Answer 24

slow waves: frequency 0.5-2 hertz
high amplitude
most often in the frontal region - propogate from cortex to hippocampus
Occurs during NREM 3-4

Question 25

SPINDLES
what is the frequency?
what is the amplitude
what does it indicate?

Answer 25

short oscillations, 12-14 hrtz
Duration 3 seconds
related to sensory gating: bursts of activity between the cortex and thalamus
NREM2

Question 26

K complexes
what is the frequency?
what is the amplitude
what does it indicate?

Answer 26

sharp, slow waves: negative and then positive
no amplitude criteria
NREM2
Also possibly related to sensory gating

Question 27

How would you differentiate NREM 3 from 4?

Answer 27

NREM 3 & 4 both show tdelta waves on the EEG, however on the EMG, in 4, there is a reduced submental tone (less oscillations)

Question 28

What would you see in REM?

Answer 28

Lots of different waves in EEG,

TONE IS NEARLY absent on EMG

Question 29

Explain a typical night sleep

Answer 29

Nearly every hour you will have a 30 minute episode of REM sleep

Question 30

What is the function of sleep?

Answer 30

Sleep is an integration of novel experiences- best evidence suggests that the principal function of sleep is memory consolidation. REM sleep seems to be a replay of the days events whilst cortex is disconnected.

Question 31

what is the ultradian rhythm?

Answer 31

timekeeping mechanisms operate at the cellular level. A shorter rhythm generator in the medulla also generates a 90 minute ultradian (more-than-daily) rhythm. Alertness/sleepiness alternate on this 90 minute cycle- during both sleep and wakefulness

Question 32

What happens when you are wide awake?

Answer 32

Ascending arousal system: brainstem nuclei send diffuse projections to the thalamus and cortex, stimulateing wakefulness. Also cholinergic drive from pons to the thalamus. NA, histamine, DA, 5-HT and orexin are significant for waking; Ach drives slow wave sleep

Question 33

What is the orexin (hypocretin) system?

Answer 33

Recently identified arousal neurotransmitter system. Lateral/posterior thalamus projection to arousal nuclei. Couples sleep/wake to metabolic cycle.s OX1R/OX2R knockout mile have disrupted sleep wake cycles, cataplexy, wake REM transitions. Autoimmune depletion of orexin (T cell cross reactivity with H1N1 influenza virus) was found in people with narcolepsy.

Question 34

What happens when it is time to sleepp?

Answer 34

The ventrolateral preoptic nucleus (VLPO) acts as the shutdown switch, sending inhibitory GABA and galanin projections to the ascending arousal nuclei to promote sleep

Question 35

What part of the cortex controls all circadian rhyth?

Answer 35

THE SUPRACHIASMATIC NUCLEUS OF THE HYPOTHALAMUS
The suprachiasmatic nucleus (SCN) of the hypothalamus uses light as a zeitgeber for the circadian cycle. An entirely separate set of visual receptors, which use the compound melanopsin to tell the SCN when it is light, was recently identified.
Circadian rhythms are largely set by the melanopsin visual system,
SCN is the master clock: As well as cueing VLPO, the SCN controls all circadian processes in the body. It manipulates core body temperature as a timing signal for clocks in various tissues. The body temperature also affected by feeding, activity, etc. and this has an effect on clocks except the SCN.

Question 36

The suprachiasmatic nucleus of the hypothalamus is the big influence in sleep patterns, but it is the _____ which triggers sleep?

Answer 36

The SCN is a big influence but the decision is made by the dorsomedial hypothalamus (DMH), which will trigger sleep when appropriate. Uses the VLPO (ventrolateralpreoptic nucleus) to ‘throw the switch’ and shut down the cortex. Other core physiology is regulated by DMH as well.

Question 37

What is zeitgeber rhythm?

Answer 37

A zeitgeber is any external or environmental cue that entrains, or synchronizes, an organism’s biological rhythms to the Earth’s 24-hour light/dark cycle and 12 month cycle

Light
Temperature
Social interactions
Pharmacological manipulation
Exercise
Eating/drinking patterns