Memory and dementia Flashcards
what is an engram?
a physical representation or location of memory
a hypothetical permanent change in the brain accounting for the existence of memory
how is learning different to memory?
learning- the acquisition of knowledge
memory- the storage of knowledge
The engram - Hebb’s law
cells that fire together, wire together
- Synapses strengthened by intense activity
- memory depends on populations of interacting neurones
- pattern of strengthened synapses defines memory
how does short term workiing mem form?
neurones innervates each other, reverberating activity
how is mem activated?
Once network of strengthened synapse formed in engram
Next time we receive a part of the input will trigger the whole network activation (smell, emotions, fear)
what is Long Term Potentiation (LTP)
does it have a voltage threshold
Glutamate produces post syn EPSP via AMPA rec, the EPSP resp gets strong and bigger after repeated stimulation gives potentiated AMPAr EPSP
YES, need enough summated AP by frequent repetitive stimulations. cant if once in a while
What are the requirements for inducing an LTP (ie reach the voltage threshold)
Need ca influx through NMDAr overcoming mg blockage
NMDA receptor – dual gating?
- Glutamate and Mg++
- glutamate alone - no current flows via
NMDAr due to Mg++ blockage.
need - large amount of glutamate release - repetitive activation of AMPAr cause depolarisation
- relieves Mg++ block
- Ca and Na influx via NMDAr
- Ca cause threshold AP cause LTP
what is very important in (control of) synaptic plasticity, learning and memory
Mg-dependent gating
How is LTP manifested?
post-syn: - more AMPAr - sensitive AMPAr, longer reaching to cell surface - more synapses pre-syn: - more amount of glutamate re per AP - more releasing sites - more glutamate vesicles
explain the MOA of LTP introduction
Phosphorylation of AMPAr by intracellular PKC/PKA- AMPAr become hypersensitive
pi of calmodulin- Insertion and synthesis of new AMPAr by CaMKII.
Retrograde messenger - nitric oxide NO from post-syn- increase presynaptic glutamate release, amount in vesicles.
Is NMDAr the only dertermining factor for LTP memory formation?
NO, other factors also involved e.g. Ach in AD, amines
LTP is induced/ expressed/ maintained by what factors?
Induced by NMDAr activation and Ca++
Expressed by AMPAr
Maintained by changes in no., sensitivity of post-syn AMPAr and no. of synpases. Also changes in amount, no. of Re site and amount in vesicles of glutamate from pre-syn. (NO –retrograde messenger increases the amount of glutamate release)
What are the 3 main types of memory:
procedural (action), emotional (love and fear), declarative (words and history)
Which brain areas in cortex are involved in memory formation:
In cortex: temporal, parietal – sensory, cingulate - remembering emotional charged events, olfactory- smell, prefrontal- risk/planning.
Which brain parts are involved in each of the type of memory?
Procedural: cerebellum, striatum, brainstem and SC/ motor output
Emotional: amygdala, hypothalamus (sexual desire, pleasure, aggression and anger)/ hormonal, autonomic output
Declarative: entorhinal (temporal lower cortex)/ parahippocampal cortex
HIPPOCAMPUS is involved in all types of memory
Genetic mutations identified in early onset AD (<65 years)
In presenilin genes - excess gamma-secretase activity – make more A-beta42 which is MOST likely to form plaques
Genetic risk factor in late onset
ApoE4 mutations - increased aggregation
what happen to henry molaison (HM)’s brain? what effect does it have?
temporal lobes removed for epilepsy. short term memory severely affected, cannot form new memory, long-term memroy is ok
Cognition enhancers - smart drugs
- cholinergic modulators: anticholinesterases- donepezil (aricept), galatamine, rivastigmine [swap if 1 fail]
agonist- nicotine - stimulants: amphentamine, methylphenidate, modafanil, caffeine
- 5HT drugs: 5HT6 antagonists
- GABAa blockers: suritozole inverse agonist bc BZ cause mem lost
- AMPA kinase- piracetam, IDRA21
- mGluR5 positive allosteric modulators
- if ChEi fails, non-competitive NMDA blocker: memantine -neuroprotective reduce cytotoxicity
2 causes for amnesia
alcohol/drug induced
head trauma : short or long term
symptoms of dementia
- 1st sign mem impairment
- general cognitive decline: risk taking, impaired judgement, spatial/ visual impairment, paraphasia, psychosis.
- inability to form new mem
- mood swing, apathy, lost of self
- diff completing familiar task - forget rule of game
- confused w time and place
is it an age dependent disease? above what age dose it likely to happen?
yes, >65 1%
>95 53%
where in the brain does alzheimer first manifest/ affect?
shrinkage of temporal and frontal cortex
damage of entorhinal cortex- memory and speech
alzheimer’s cellular pathology, what are the diagnostic hallmarks?
- NP neuritic plaques, extracellular insoluble amyloid- beta- protein
- NFT neurofribrillary tangles, intracellular cytoskeletal protein tau
which neurones were the first to be affected/ cell death?
ach and glutamate