memory Flashcards
define learning
acquisition of information
define memory
storage of learned information
define recall
reacquisition of stored info
define engram
physical embodiment of memory
independent memory systems
procedural = actions, skills - implicit - unavailable for conscious mind
declarative = knowledge, in words - explicit - available to conscious mind
explicit = consciously recalled
implicit = not consciously recalled (e.g. procedural, classical conditioning, priming)
duration of memory
immediate = few seconds
STM = seconds - minutes (working memory)
LTM = infinite
role of temporal lobe in memory
electrical stimulation of temporal lobe = hallucinations and recollection of past experiences
epileptic seizures = complex sensations and memories
patient HM = removal of part of temporal lobe due to epilepsy - maintained personality and intelligence, had extreme anterograde amnesia – no new memories - good working memories but couldn’t form new LTM
brain structures and memory: PFC
involved in working memory
brain structures and memory: hippocampus
converts STM to LTM - declarative memory
lesions here cause memory loss (HM)
structure = 3 layers of cortex
input from entorhinal cortex and beyond
outputs to many regions
enlarged in people who require good spatial memory - London taxi drivers
brain structures and memory: amygdala
processed sensory inputs (e.g. smell), implicit emotions and learnt fear
brain structures and memory: cerebellum
procedural memory, sensorimotor processing occurs here too
mechanisms of memory - reverberating circuits
reverberating circuits = nerve impulses that were initially activated in response to stimuli are reactivated to recall information
memorising = dedicating neurons to this
active = remembering
inactive = not remembering
Hebbian synapse concept
2 neurons active at same time = connection become stronger between them - leads to memory
2 neurons active at different times = connection between them weakens
activity is modifiable - plastic synapse
synaptic plasticity
synaptic strength changes
facilitation or depression (strengthen or weaken)
short term (mins/hours):
Ca2+ availability / vesicle depletion -> not enough vesicles at presynaptic site = weakening of connection and depression
long term facilitation/depression:
sustained over days/weeks
mostly involves post-synaptic changes
long term potentiation
persistent strengthening of synapses - increase in EPSP amplitudes
tetanic long term potentiation
stimulating presynaptic neuron in high frequency bursts - leads to increased EPSP
paired long term potentiation
stimulate pre and post synaptic at same time - coincident stimulus and depolarisation –> increased EPSP
explains classical conditioning - association of one stimulus with another, occur at same time, strengthens synapse between
long term depression
LTD in hippocampus, decrease in amplitude of EPSP, weakening of synapse
short-term habituation and sensitisation
habituation = decrease in response to same stimulus - get used to it
sensitisation = increase in response to same stimulus
short term habituation and sensitisation animal studies
sea slugs
modify behaviours with gill withdrawal reflex
shocking tail = gill withdraws
touching after shock = quicker withdrawal = sensitisation
repeated gentle stimuli to tail = reduced gill withdrawal = habituation
LTP with sea slugs
require receptor activation (glutamate, serotonin) - altered synaptic responsivity
mediated by secondary messengers (Ca2+ and cAMP)
— critical role of Ca2+ as a secondary messenger - activates protein kinases which phosphorylate proteins and increase AMPA receptors activity
trafficking of AMPA receptors to postsynaptic membrane
early stages require protein phosphorylation changes, late stages require protein synthesis
biochemical and structural pre and post synaptic changes
