Learning and memory Flashcards
define learning:
acquisition of knowledge that will modify subsequent behaviours
define memory:
ability to recall or express past experiences
list some types of learning:
- non-associative learning
- associative
- observational
learning: non-associative types
- sensitisation
- habituation
learning: non-associative sensitisation
enhanced behavioural response following noxious stimulus
- unpleasant
learning: non-associative habituation
decreased behavioural response following repeated presentation of neutral stimulus
learning: associative types
- classical conditioning
- operant conditioning
learning: associative classical conditioning
- eg. Pavlov’s dog (salivation when bell is rung)
- involuntary reflexive behaviour
- animal ‘learns’ that conditioned stimulus (CS: bell) precedes ‘unconditioned’ stimulus (US: food)
learning: associative operant conditioning
- eg. Skinner box
- voluntary behavioural outcome
- animal learns to associate behavioural choice (coloured light) with outcome/ consequence (punishment/ reward)
learning: observational learning
- learning by observing others
- not necessarily require reinforcement
memory classified functionally depending on:
- duration
- context
- level of top-down control/ conscious awareness
memory pathway: information into
- short term (working memory)
- long term
memory pathway: long term into
- explicit
- implicit
memory pathway: explicit (declarative) into
- episodic (events)
- semantic (facts)
- spatial (places)
memory pathway: implicit (non-declarative) into
- procedural (motor tasks)
- priming (associations)
- associative learning
- non-associative learning
short term memory: features
- last few secs
- store info temporarily for subsequent recall
- eg. remembering telephone no.
working memory: features
- store info temporarily while executing a task
- eg. remembering set of no. when doin sum
- represents framework where prefrontal cortex controls 2 neural loops that serve to hold data ‘in mind’ while task is performed
1. visual loop (PFC and visual cortex ‘scratch pad’
2. phonological loop (PFC, Broca’s and Wernicke’s areas)
long term memory: define
explicit (declarative) memory- conscious effort needed to retrieve memories of past events
long term memory eg: episodic
- relate to experiences in your life
- eg. holiday, first kiss
long term memory eg: semantic
- facts or general knowledge
- eg. knowing roughly 90 billion neurons in brain
long term memory eg: spatial
- orientation and navigation
- eg. knowing where you are/ how to get somewhere
long term memory: neocortex
memories transferred from hippocampus during sleep
long term memory: hippocampus
= archicortex in medial temporal lobe
- storage and indexing of memories for later recall
long term memory: amygdala
influences strength of memories due to emotional salience (prominent)
long term memory: implicit (non-declarative) memory define
automatic recall wit lil/ no conscious effort
long term memory: implicit memory types
- procedural
- priming
- associative learning
- non-associative learning
long term memory: implicit memory procedural
- automatic motor task
- eg. driving car, riding a bike
long term memory: implicit memory priming
- activating an association in memory (semantic, perceptual, conceptual)
- eg. showing someone word ‘yellow’ generate faster response to banana vs ‘phone’
long term memory: implicit memory - priming brain part used
- neocortex
- especially PFC and extrastriate cortex
long term memory: implicit memory - procedural memory brain part used
- dorsal striatum (caudate, putamen)
- cerebellum
long term memory: implicit memory associative learning
- classic conditioning, operant conditioning
long term memory: implicit memory associative learning - skeletal musculature?
cerebellum
long term memory: implicit memory associative learning - emotional response
amygdala
long term memory: implicit memory associative learning - reward
ventral striatum (nucleus accumbens)
long term memory: implicit memory non-associative learning part of brain
- sensitisation, habituation
reflex pathways
neuroplasticity: short term memory
- synaptic plasticity (eg. presynaptic facilitation)
- changes in release and function of NTs
neuroplasticity: long term memory
- synaptic plasticity (eg. long term potentiation)
- structural plasticity= rewriring/ new synapses/ new neurons
- synthesis of new proteins (eg. receptors), formation or elimination of synapses
sensitisation of gill withdrawal reflex in Aplysia: brief description
- apylsia withdraws gill when siphon is touched
- if noxious stimulus to another part of body, gill withdrawn rapidly
- next time siphon touched again, gill withdrawn faster and longer
- tail shock lasts mins, repeated even longer-lasting sensitisation
sensitisation of gill withdrawal reflex in Aplysia: what type of learning
non-associative learning
action potential in Aplysia: distal end of siphon sensory neuron
identical before/ after sensitisation
action potential in Aplysia: axon terminal of siphon sensory neuron
lasts longer after sensitisation
action potential in Aplysia: prolonged glutamate release causes
stronger response (depolarisation) in gill motor neuron
long term learning: rabbit hippocampus after intense/ repeated stimulation of presynaptic neuron
- amplitude of postsynaptic potential increased
long term potentiation (LTP): define
long term strengthening of synaptic activity
long term potentiation (LTP): induced by
- brief (secs) high frequency (100Hz) bursts/ tetanus of action potentials
long term potentiation (LTP): hippocampus importance
responsible for formation and retrieval of long lasting explicit (declarative) memories (facts/ events)
long term potentiation (LTP): damage to hippocampus
prevent formation of new explicit memories
long term potentiation (LTP): unaffected memory by hippocampus
implicit (procedural) memory (things done unconsciously)
long term potentiation (LTP): also observed where
- involved in forming memories
- neocortex
long term potentiation (LTP): not observed where
- areas not involved in memory formation
- eg. brainstem
long term potentiation (LTP): role of hippocampus in explicit (spatial) memory
- rodents in Morris water maze
- control rats after 10 trials swam straight to second platform using environmental cues
- rats w hippocampal lesions still could not remember where to find platform
long term potentiation (LTP): types of ligand (glutamate) ion channels (ionotropic) receptors
- AMPA (permeable to Na and K)
- NMDA (permeable to Na, K, and Ca- normally blocked by Mg ions)
long term potentiation (LTP) mechanism: weak stimulus
- single AP in presynaptic terminal causes limited glutamate release
- NMDA receptors blocked by Mg ions
- Na influx generates depolarisation and small EPSP
long term potentiation (LTP) mechanism: strong stimulus
- multiple APs in presynaptic cell
- larger glutamate release
- AMPA channels open
- Na influx depolarises
- spatial and temporal summation of EPSPs generates large depolarisation (grand PSP) in postsynaptic cell
- Mg ion forced out of NMDA receptors
- influx Ca
long term potentiation (LTP) mechanism: Ca importance
- intracellular signalling molecule
- tiggers many mechanisms to increase synaptic strength
long term potentiation (LTP) mechanism: rapid and large increase of Ca activates enzymes (kinases) causing
- phosphorylation (modification) of AMPA receptors: stay open and let in more Na
- insert more AMPA receptors into membrane (upregulation of gene expression and protein synthesis)
- release ‘retrograde messengers’ (eg. nitric oxide): presynaptic neuron release more glutamate when active
- physical changes to neurons (eg. synapses get bigger)
long term potentiation (LTP) mechanism: all activity due to Ca is to
- bring postsynaptic Vm closer to threshold when synapse is active in future
long term potentiation (LTP): characteristics critical for selective strengthening of particular synapses during formation of memories
- specificity
- associativity
long term potentiation (LTP): characteristics specificity
- high activity in pathway 1 induces LTP in that synapse, but not at other inactive synapses from different pathways (2) that converge on same cel
long term potentiation (LTP): characteristics associativity
- weak stimulus in pathway 2 does not produce LTP
- but strong stimulus to pathway 1 at same time as weak stimulus at 2, both synapses show LTP and are strengthened
long term depression (LTD): features
- enhance synaptic transmission and strengthens important neural pathways
- need mechanism to weaken synapses for extended durations
- help efficient functioning of procedural (implicit) memory: unconscious tasks
- may help weaken synapses which lead to errors when learning motor behaviours
long term depression (LTD): observed where
- cerebellum (motor learning)
- visual cortex
- hippocampus (memory decay)
- corpus striatum
long term depression (LTD): triggered by
- low frequency (1-5Hz) stimulation of presynaptic neuron
long term depression (LTD): Ca conc.
- slow, small and long lasting rise of Ca
long term depression (LTD): in cerebellum
- slow increase activate kinases -> phosphorylate AMPA receptors = internalised (removed) from membrane
long term depression (LTD): in hippocampus
- slow increase activates phosphatases -> dephosphorylate AMPA = internalised
long term depression (LTD): both mechanisms cause
- reduced permeability of postsynaptic membrane to NA
- fewer AP generated in postsynaptic cell when presynaptic cell is active
- synapse gets weaker
structural plasticity: addition/ removal of synapses - dendritic spines
- predominant site of excitatory synaptic input to many neurons in CNS
- hippocampus, cerebellum etc
structural plasticity: addition/ removal of synapses - dendritic spines importance
- formation/ elimination of dendritic spines (and synapses) responsible for neural connectivity changes underlying storage of memories
- dendritic spines= structural units of memory
structural plasticity: addition/ removal of synapses -mouse motor cortex
- addition of new spines following motor learning
- neurons activated during learning and reactivated in REM sleep
- sleep disruption prevents new spine formation
- sleep crucial for promoting synaptic plasticity underlying memory formation
structural plasticity: addition/ removal of neurons - post hippocampus importance
- spatial navigation
structural plasticity: addition/ removal of neurons eg. London black-cab drivers
- enlarged post hippocampus
- correlated w time spent driving
- not in bus drivers
- 2-4 yrs training
- 25000 streets
memory and limbic system: storage of memories dependent on
- salience of experience/ association
- eg. level of attention/ emotional context (pleasure, fear)
memory and limbic system: involves
- cortex
- limbic structures (hippocampus, amygdala, hypothalamus etc)
memory and limbic system: to be stored as long term memory must pass and why
circuit of Papez
- associations formed in cortex pass repeatedly through circuit -> consolidation of memories stored in modality specific areas of cortex
memory and limbic system: damage to hippocampus
- prevents forming new memories
- doesn’t affect old memories
memory and limbic system: limbic system involved in
learning and forming memories concerning emotional stimuli
memory and limbic system: amygdala influences
our response to emotional stimuli
- esp aversive/ fearful ones
implicit (unconscious) emotional memory
memory and limbic system: hippocampus encodes
- semantic and episodic context associated w emotional stimulus
explicit (conscious) emotional memory
memory and limbic system: emotional stimuli reach amygdala by
- direct (fast/ short) but imprecise
- indirect (slow/ long) but precise
memory and limbic system: direct route to amygdala
thalamus -> amygdala
- subcortical route
memory and limbic system: indirect route to amygdala
thalamus - cortex - amygdala/ hippocampus -> amygdala
- cortical route
how does cortex moderate responses: brief
exerts executive control
how does hippocampus moderate responses: brief
provides context
maturation: amygdala
matures earlier in life
maturation: hippocampus
- slower and continues into teen yrs
- conscious recall of childhood experiences poor
- early childhood traumas stored in amygdala may subconsciously influence mental/ behavioural function in adults
