Memory Flashcards
what famous patient lent great insight into hippocampal dependent memory
HM had both hippocampal regions removed
HM had bike accident when a child, had epileptic fits and didn’t respond to drugs.
Experimental surgery on his brain -
Bilateral resection of the medial temporal lobe, to relieve severe epilepsy
Profound memory impairment (scenes, words, faces)
Learnt a hand – eye coordination skill (mirror drawing) over a period of 3 days (motor skills?).(wouldn’t remember learning it but would get better at it
what is priming (nondeclarative memory)
a phenomenon in which previous stimuli influence how people react to subsequent stimuli
(improves ability to detect produce or classify an item)
encoding new information requires which brain structure
medial temporal lobe
what are the two types of long term memory
declarative and nondeclarative
what are the two types of declarative memory
episodic (events) and semantic (facts) memory
what structure processes declarative memory
medial temporal lobe and diencephalon
what are the 4 types of nondeclarative memory
procedural memory
priming
simple classical conditioning
nonassociative memory (habituation/ sensitisation)
where is procedural memory processed
basal ganglia
what is procedural memory
a type of long-term memory involved in the performance of different actions and skills
(habits)
(characterised by automatized, repetitive behaviour
what is an engram
the physical embodiment of any memory in neuronal machinery
what does an engram depend on
changes in synaptic connections and/or actual growth and reordering of such connections
what brain structure is associated with priming
neocortex
what area of the brain is associated with simple classical conditioning
amygdala and cerebellum
what part of the central nervous system is involved in habituation and sensitisation
reflex pathways
how is declarative memory expressed
expressed through recollection
how is nondeclarative memory expressed
expressed as personality or attitude and through performance
what is nonassoiative memory
a process in which an organism’s behavior toward a specific stimulus changes over time in the absence of any evident link to (association with) consequences or other stimuli that would induce such change
(based on frequency)
which type of long term memory is more malleable
declarative
what are the unimodal and polymodal association areas that input to the cortex
frontal temporal and parietal lobes (sounds smell vision)
which cortices study objects and scenes of declarative memory
The perirhinal cortex studies objects and the Para-hippocampal cortex recognizes scenes.
.
how do the recognition of objects and scenes get processed in declarative memory
the perirhinal cortex (objects) and the parahippocampal cortex project to the entorhinal cortex which brings them both into the hippocampus (through into the trisynaptic circuit)
what are the parts of the trisynaptic circuit in the hippocampus
Tri-synaptic circuit in hippocampus is the dentate gyrus, CA3 and CA1.
what is eyeblink conditioning and lesions in what two areas impair this
Tone and puff of air applied at the same time.
Air puff would cause a blink, eventually subject will learn the tone leads to the puff and will blink.
Cerebellar and brainstem lesions impair this type of conditions.
the amygdala has a critical role in what type of learning and is activated by what
a critical role in fear learning.
activated by fear and strongly positive emotions
what is evaluative information
Positive vs Negative value / non-declarative
how is fear learning measured in animals
by a fear expression of freezing
what action is involved in the reversal of fear learning
inhibitory action of the prefrontal cortex on the amygdala
how do emotionally arousing events enhance memory
the amygdala causes release of stress hormones from the adrenal gland, which affects the forebrain via the vagus nerve, the nucleus of the solitary tract and the locus coeruleus
the locus coeruleus releases noradrenaline that can modulate functions of neurons and glia
what makes up the neostriatum
the caudate nucleus and putamen
the caudate nucleus is important for what system and functions in what loop that is involved in goal directed behaviour
Brain’s reward system and functions as part of the cortico–basal ganglia–thalamic loop
what two strategies are used to solve a maze and what areas of the brain do they use
Spatial -Hippocampal: navigating in relation to landmarks
Non-spatial (habit like) Striatal Caudate nucleus: Counting maze arms
what group of synapses in the hippocampus has efficacy that is influenced by activity several hours previously
the perforant pathway to the dentate gyrus glutaminergic synapses
what are place cells
a kind of pyramidal neuron in the hippocampus that becomes active when an animal enters a particular place in its environment, which is known as the place field.
Act collectively as a cognitive representation of a specific location in space, known as a cognitive map
why have the CA3->CA1 connections be studied more than the entorhinal cortex to dentate gyrus (perforant pathway)
more experiments have been done because it is a simpler pathway
what are the mechanisms of plasticity
addition of AMPA receptors to the post synaptic membrane (using dendritic ribosomes) by influx of Ca++ through voltage gated NMDA receptors triggered by glutamate release and post synaptic membrane depolarisation
changes in presynaptic release in glutamate mediates the (NMDA independent) mossy fibre-CA3 synapses (requires >1 or bursts of stimuli - detonator dependent)
what is a possible mechanism to switch off plasticity
apply an inhibitor of glutamate NMDA receptors
how are NMDA receptors voltage dependent
because of Mg++ blockage
positive charge expels the magnesium ion opening the channel - it needs cells to be active to open
how do NMDA receptors act as coincidence detectors
They only open when there is glutamate release and postsynaptic depolarisation
(positive charge expels the Mg ion)
what is the biological basis of presynaptic short term plasticity created in mossy fibre-CA3 synapses
Unitary EPSPs not sufficient to initiate a spike in CA3 neurons under control conditions, but reliably cause action potentials if stimuli delivered in “bursts”
- plasticity due to a change in the R type alpha 1E containing Ca++ channels (mediated by presynaptic release of glutamate)
what is unique/remarkable about mossy fibre-CA3 synapses
unusually high degree of facilitation during repetitive stimulation - after first action potential is created the second one is massive because of a high number of vesicles ready to go
plasticity dependent detonation is critical for what parts of memory
for efficient coding, storage, and recall of information in the granule cell–CA3 cell network.
what is the ‘full detonator mode’ in mossy fibre synapses
With longer bursts (100 stimuli in 1 second) plasticity can be extended for tens of seconds to allow “full detonator mode” for tens of seconds after high frequency stimulation
may allow a single highly specific cue to trigger the encoding, storage, or recall of complex information in CA3 pyramidal neurons
what are the key neuronal elements of alzheimers
it starts will loss of procedural memory. Early phases affect entorhinal cortex and hippocampal formation. Lack of communication between the two could be the reason for the mild cognitive impairment
hippocampal damage always equals….
….lack of capacity to create new memories
what is korsakoffs syndrome
a disorder that primarily affects the memory system in the brain. It usually results from a deficiency of thiamine (vitamin B1), which may be caused by alcohol abuse, dietary deficiencies, prolonged vomiting, eating disorders, or the effects of chemotherapy
at a network level what regions of the brain are involved in memory
entorhinal cortex, lateral amygdala, association cortices, basal ganglia and hippocampus.
what is short term sensitisation due to
an acute, PKA-dependent enhancement of glutamate release from the presynaptic terminals of sensory neurons - a type of plasticity
what is long term sensitisation due to
due to changes in gene expression, causing expression of proteins that change PKA activity and lead to changes in synapse growth - a type of plasticity
how does sensitisation take place
serotonergic interneurons release serotonin causing release of G proteins causing production of cAMP (via adenyl cyclase) and activation protein kinase A which causes down regulation of potassium channels (increasing calcium entry) causing more neurotransmitter to be released
- generally inhibition of potassium channels helps longer term release of glutamate
what is anterograde amnesia
loss of the ability to create new memories (due to an amnesia event)
what is retrograde amnesia
inability to remember past events or experiences.
if an engram is not yet a memory what is it and when does it become one
An engram is not yet a memory, but provides the necessary physical conditions for a memory to emerge.
A memory emerges when appropriate retrieval cues reactivate an engram
3 things Engram cells are:
1) Activated by a learning experience,
2) Physically or chemically changed by the learning experience, and
3) Reactivated by subsequent presentation of the stimuli present at the learning experience
what is the Morris water maze experiment
Tank of water painted white. Platform under the water, can’t be seen while swimming. Rat will swim around until they find the platform, repeat this test, by the second or third day they know where to go no matter where in the maze you put them. take out platform, they search in a similar area
- test with different brain lesions/ NMDA blockers
contextual fear learning uses activation of widely distributes neuronal ensembles in which areas
entorhinal cortex, the dentate gyrus, and lateral amygdala (LA).
a given memory is stored in….
functionally connected multiple engram cells dispersed in multiple brain regions: the entorhinal cortex, the hippocampus and the amygdala
