Memory Flashcards
learning =
acquisition of information
memory =
storage of learnt information
recall =
requisition of stored information
the engram =
physical embodiment of memory
independant memory systems
different forms of memory stored in different ways/regions/pathways
e.g. playing piano - auditory cortex and motor cortex
procedural memory
skills and associations largely unavailable to concious mind
declaritive memory
available to concious mind
can be encoded in symbols and language
explicit memory
memory that can be coniously recalled
implicit
memory that cannot be conciously recalled different types: - procedural memory - classical conditioning - priming
memory duration
immediate - few seconds
short term - seconds or mins
- working memory
long term - days, months, lifetime
temporal lobe and memory
electrical stimulation - hallucinations and recollection of the past experiences
epileptic seizures - complex sensations and memories
patient HM - temporal lobectomy
8cm of medial temporal lobe was removed
intelligence, personality intact etc
epilepsy stopped
extreme anterograde amnesia - cannot form new memories
important structures
pre frontal cortex - working memory
hippocampus - converting short to long term memory, declaritive memory
amygdala - multiple processed sensory input (smell), implicit/emotional/learnt fear
cerebellum - procedural memory, sensorimotor
hippocampus
hippocampul lesions caused memory loss
three layered cortex
- inputs from entorhinal cortex and beyond
- outputs many regions
- enlarged in people whose work requires good spatial memory
mechanisms of memory
long term storage seems to be distributed
reverberating circuits - idea that memory is constant activity of neurons - not supported by experiemtal evidence
instead …. the hebbian synapse concept - change in synapse number between neurons
- activity modifiable, plastic synapses
memory and synaptic plasticity
synaptic strength changes
facilitation / depression
- short term - mins/hrs —> Ca availability/vesicle depletion
- long term - days/weeks
long term potentiation (facilitation)
studied in hippocampus slices
= increase in synaptic strength
CA3 - presynaptic neurons
CA1 - postsynaptic neuron
stimulate presyn with short high frequency bursts - EPSP increases
changes in synapses are very local, specifc pathway
long term depression
in hippocapmus
EPSP amplitude decreases with time with a prolonged low frequency stimulation of presyn
aplysia californica
large snail
gill withdrawl reflex
small number of neurons
short term habituation and sensitisation
repeated gentle stimulation to siphon causes reduced gill withdrawal
- habituation
pair single tail pinch with siphon touch - leads to increased withdrawl of gill
- re establish siphone reflex, short term 60 mins +
long term sensitisation
repeated pairing of siphon touch and tail pinch
- long term, non habituating siphon/gill reflex
long term potentiation, depression and aplysia
require receptor activation (glutamate/seratonin)
altered synapse responses
mediated by second messenger (Ca/cAMP)
require protein phosphorylation changes in early stages
require protein synthesis for late stages
involve biochemical and structural pre and post syn changes
how does long term potentiation occur?
evidence suggests often a post syn event
most indicates a critical role for Ca
involves trafficking of AMPA receptors to post syn membrane = inc in ESPS
