Chapt. 12 - Memory Modulation Flashcards
If you don’t have a ____ you won’t have memory modulation
amygdala
Why are arousing experiences memorable
arousing events activate the neural and hormonal processes the influence the cellular-molecular processes that consolidate memory
emotional experiences encode AND activate systems that impact consolidation
Explain the memory modulation framework (specifically the independent effects of experience)
(James McGaugh)
experience has two independent effects.
1. it can initiate acquisition and storage of the memory tract
2. and it can activate the release of adrenal hormones that can modulate the processes that store the memory
Memory modulators
the hormones and other neural systems that are not part of the storage system of memory but they influence the synapses that store the memory.
they have a time-limited role, they can only influence storage of very recently acquired memories, usually few hours to improve of impair the representation
Huston memory modulation experiment
trained mice on passive (dont move and be good) avoidance task, where animals shocked if stepped down. some mice were fed in their home cages immediately after stepping down and receiving a shock –> these mice remained on the platform longer than those that did no get fed, enhancing memory and performing better.
food modulated memory, because was in a timeline where could be modulated
What is memory consolidation
(muller and pilzecker)
hypothetical process by which the labile (easily changeable) neural representation of a memory that exists immediately after is it formed, changes over time into a relatively permanent representation
Post training events can ___ consolidation processes while others can ____ the process
disrupt
enhance
(events during the labile period can have these effects)
What is considered the great modulator of memories and why
The basolateral amygdala because it is anatomically connected to many brain regions that are storage sites for different memories. It is in a position to influence and modulate storage processes in other regions of the brain.
The amygdala itself is not a STORAGE SITE
Results of place learning water task with injection of amphetamine into basolateral amygdala
injected at a specific time (treatment of immediately after or 6 hours after training) the immediately after improved retention performance
hippocampus thought to be critical storage site for this task
Results of injected amphetamine into basolateral amygdala following training of visible platform task
improved retention (short latency means better retention)
dorsal striatum thought to be critical for this
Explain post training memory improvement paradigm
second day of training, give injections. post training with amphetamine, next day is drug free and they do significantly better.
Lidocaines effect on retention depends on…
Explain!
where it is injected
lidocaine temporarily shuts down whatever system is it injected into and impairs it (longer the latency the better the memory)
1. injection into basal nucleus of basolateral amygdala after avoidance training, impaired retention of the inhibitory avoidance response
2. injection into central nucleus of amygdala had no effect (because not actually part of memory modulation)
Adrenal glands and composed of what two parts
endocrine gland located above the kidney
1. adrenal medulla - secretes epinephrine
2. adrenal cortex - secretes glucocorticoids
____ that is released by the adrenal ____ plays a major role in memory modulation processes
epinephrine
medulla
problem with epinephrine molecules
they are too large in the blood to cross the blood brain barrier so need to find a different way to influence the amygdala.
What are the ways that epinephrine molecules are able to influence the amygdala
because too large to cross the blood/brain barrier
use parallel processes of the cranial nerve and the liver
Epinephrine uses the cranial nerves to send information about the body to the brain by…
the vagus nerve arises from the medulla supplying the internal organs (viscera) of the thoracic and abdominal cavities
Epinephrine enhances memory for inhibitory avoidance training experiment
rats receive mild shock when cross into dark side of the room. control receives vehicle, and treatment is injected with dose of epinephrine - dose is to mimic the level released if an animal experienced a strong shock. Treatment showed improved response (increased latency), but was time dependent/ ex. effects didn’t last over 30 mins to be affective
Explain the Epinephrine and Vagus connection
epinephrine when released from the medulla, binds to adrenergic receptors of the vagal nerve. If activated, vagal nerve releases glutamate on neurons in the solitary tract nucleus (NTS).
the activated NTS neurons release glutamate in the locus coeruleus, which release norepinephrine that binds to adrenergic receptors in the basolateral amygdala.
disrupting any component will prevent arousal of enhancing memory
Microdialysis allows…
extracellular fluid to be collected from deep within the brain
1. rat implanted microdialysis probe in the brain
2. freely moving rat connected to instrumentation designed to extract small quantity of extracellular fluid and other content and then analyzed for its composition
(want to see if norepinephrine is released)
microdialysis used to extract norepinephrine from the extracellular brain fluid and found 3 things
- level of norepinephrine released in fluid in inhibitory avoidance training is determined by the intensity of the shock
- just shocking a rat or allowing it to explore does not increase level of norepinephrine
- requires the rat to both explore and be shocked
Norepinephrine injected in amygdala improves retention performance
inject after place learning, enhances rats retention of the platform location or inject propranolol to block learning and impair.
NE injected after weak shock (enhanced)
Propranolol injected after strong shock (impaired)
Experiment to see what does the amygdala signal do (arc translation experiment DESIGN)
insert tube used to administrate medicine
rats trained on inhibitory avoidance task
either injected with b-andrenergic agonist (help) or lidocaine (shut down)
rats either sacrificed or tests on task
hippocampus brain tissue was sample for arc protein
Results of arc translation experiment/ amygdala signal
the arc protein is important for long term retention and there are opposite effects of enhancing (b-andrenergic agonsit) or lidocaine (shut down/reduce levels of arc protein) on inhibitory avoidance learning
Define bioenergetics and the source of energy is
the flow of energy in cells and the primary source of energy is glucose which enters the brain via the cerebral vasculature.
epinephrine modulates memory by
binding to adrenergic receptors on the liver cells causing them to release glucose
Response to foot shock, _____ releases epinephrine in both young and old rats while in the liver of only ____ rats secrete glucose
adrenal gland
young
Only ___ rats show increase in shock intensity because of the increase in glucose
young (because also secrete in liver)
What four experiments did Mcdonald perform to test amygdala being crucial modulator of memory
- water maze
- long term retention
- one trail place learning
- post training memory improvement
Water task to show amygdala is crucial modulator of memory
no impact on water task with impaired amygdala
(head direction, path length, or latency)
Long term retention to show amygdala is crucial modulator of memory
24 hour retention, bring them back after 24 hours
no difference in heading angle or quadrant preference.
unusual that they still show strong representation without amygdala after 30 days but technically still works
One trail place learning to support that amygdala is crucial memory modulator
find new place every day
no difference with or without amygdala (place control is highly dependent on the hippocampus)
Retention place learning to support that amygdala is crucial memory modulator
go for first swim, taken back to homes, then 24 hours later taken for their second swim
no difference between groups! (path length, head direction, latency)
____ injection had the best post training memory modulation of the water maze task
amphetamine
The dominant role of the amygdala is _____
also involved in _____
classical conditioning
memory MODULATION
Is the amygdala necessary for activation of memories
No, it is involved and can modulate, but there are other parallel pathways that can modulate instead
