Memory and sleep Flashcards
What is the engram
The physical embodiment of a memory
What are the 2 memory systems
Procedural memory (implicit) - skills and associations, unavailable to the conscious mind
Declarative (explicit) - available to the conscious mind, symbols and language
What are the different lengths of memory
Immediate - few seconds
Short term - seconds/mins
Long - days,months,years
What parts of the brain does playing the piano require
Auditory cortex and motor cortex
What parts of the brain does taking an exam require
Amygdala and frontal cortex
What does the temporal lobe do
Responsible for creating and preserving conscious and long-term memory
Patient HM had 8cm of medial temporal lobe removed –> intelligence and personality was intact but had extreme anterograde amnesia
What does the pre-frontal cortex do
Allows access to the working memory
What does the hippocampus do
Converts short - long term memory
Declarative memory
What does the amygdala do in memory
Multiple processed sensory inputs which allow for learnt fear
What does the cerebellum do in memory
Procedural memory
Sensorimotor memory - difference between you and environment
How many layers in the hippocampus
3 layered cortex
Where does the hippocampus get its inputs
Mainly the entorhinal cortex
When would the hippocampus be enlarged
In people whose work requires good spatial memory
What are reverberating ciruits
A neural circuit which nerve impulses that were initially activated in response to stimulus are more or less continuously reactivated so that he retrieval of information on demand is possible
What is the Hebbian synapse
A junction between neurons which is strengthened every time it successfully fires
What is long term potentiation
a process involving persistent strengthening of synapses that leads to a long-lasting increase in signal transmission between neurons
What is in the temporal lobe
the olfactory cortex, the hippocampus and the amygdala
What is long term depression
The process at which synaptic connections become weaker
Allows for new memories
How does LTD occur
NMDA blocked by Mg2+
AMPA activation causes depolarisation so Mg2+ removed
Ca2+ can re-enter the neuron causing further depolarisation
Low level of calcium is insufficient to activate LTP
Activates cellular cascade to remove AMPA receptors which weakens the synapse
When does LTD happen
Prolonged low intensity stimulation
How does LTP occur
Mg2+ block on NMDA receptors removed by glutamate so Ca2+ can enter the cell
Influx of calcium creates more AMPA receptors so more postively charged ions can enter the cell
Postsynaptic receptor becomes more receptive to glutamate so more Ca2+ can enter
What is habituation
A decrease in response to a stimulus after repeated presentations
How is habituation achieveved
Repeated stimuation calcium channels becomes less responsive so less calcium crosses the presynaptic membrane
Less neurotransmitter released
Less depolarisation of the post-synaptic membrane so no action potential is triggered in the motor neuron
What changes in habituation
Less neurotransmitters so fewer APs
What is short term habituation
Attenuation of the startle response on repeated presentation of the startle stimulus
Lasts several minutes
What was the animal where habituation was first researched
Aplsia califonica (big snail)
How is long term sensitization achieved in aplysia snail
Pairing of tail and siphon stimulus shows that the gill withdrawal reflex can be altered for days or weeks
What is the definition of sleep
A period of reduced motor activity, reduced response to stimulation, stereotypic postures, easy to reverse
What does electroencephalogram measure
electrical activity of neurones in the brain
What are the advantageous of electroencephalogram (EEG)
Non-invasive
Easy to administer and gather data
High temporal resolution (milliseconds)
What are the disadvantageous of electroencephalogram
Low spatial resolution
Further away from source the smaller the signals and the skull blocks some of the signals
What are the 4 types of brain waves
Beta - high Hz
Alpha
Theta
Delta
What are the 5 stages of sleep and what does each of the measurement tools show
Drowsiness - awakened easily, eyes move slowly and muscle activity slows. EOG shows slow rolling of eyes
EMG shows some muscle activity
EEG shows mostly theta waves
Preparation for deep sleep, Heart rate slows and body temperature drops
EOG is greater than stage one, EMG similar to stage one, EEG greater than stage one
Deep sleep. Extremely slow delta waves with smaller faster waves interspersed in-between. Phase of night terrors, sleep talking
EOG is greater than stage 1 and 2
EMG is consistent with 1 and 2
EEG is much higher
Very deep sleep
EEG - brian produces delta waves
Disorientation from arousal
EOG and EEG similar to stage 3
REM sleep, EEG mimics wakefulness, eyes move rapidly side to side, intense dream and brain activity, sleep is paradoxical
What does a electromyograph show (EMG)
Muscle movement
What does a electro-oculograph show (EOG)
Eye movement
How many times is REM repeated per sleep
4 or 5 times in a night
stage 3 and 4 decrease in duration throughout the sleep
What are the percentages of time spent asleep in each stage
5% - stage 1
50-60 stage 2
15-20 stage 3 and 4
20 stage 5
What part of the brain regulates wakefulness
Brain stem
What are 5HT receptors
a group of G protein-coupled receptors specific for serotonin
What is paradoxical sleep
REM-neurons firing like wakefulness
What systems are activated in REM sleep
No activity in frontal lobe
No activity in raphe nuclei and locus coeruleus
Inhibition of motor neurons
What is the purpose of sleep (theories)
Exercise the synapse
Circuit testing
Memory consolidation
What is the major internal clock
Suprachiasmatic nucleus of anterior hypothalamus
Regulates timing not the sleep itself
What provides information to the suprachiamsatic nucleus
Photosensitive ganglion cells
Sense light - dampens the suprachiasmatic nucleus
What does the raphe nucei do
Releases serotonin (5-HT)
What is the locus coeruleus
Where the brain creates Norepinephrine
