Learning and Memory

Learning and Memory

1. Atkinson and Shiffrin

   • immediate/sensory memory
   • STM
     • sometimes working memory
   • LTM
     • transfer to here is consolidation
     • consolidation occurs via rehearsal

2. types of memory

   • explicit/declarative
     • episodic
     • semantic
   • implicit/non-declarative
     • associative
       • classical
       • operant
     • non-associative
       • habituation
       • sensitization

3. associative conditioning forms

   • classical conditioning
     • relation between two stimuli
       • reflexive learning between US and CS
     • Pavlov
     • not conscious- innate response
     • not all reflexes work this way
     • Lashly
       • engram/memory trace identification
       • Law of Mass Action- severity of beh deficit with AMOUNT of damage
       • mistakes
         • assume cortex best for engram search
         • assumes all mem types same
   • instrumental conditioning
     • stimulus/consequence relationship
       • reinforcing
       • punishing
     • Thorndike's cat
       • positive and negative reinforcers
     • Skinner
       • later calls this operant conditioning
         • behavior
         • reinforcer or punisher
         • discriminative stimulus
     • neural modelling
       • strengthen connections
         • reinforcing stimulus
         • mesolimbic dopamine system
       • Hebb's rule
         • structural/chem change to strengthen
         • leads to synaptic plasticity idea
         • leads to LTP idea
           • LTP at synapses when memories created
           • hippocampus
             • layered
             • entorhinal cortex to neurons in HI has 3 paths
               • perforant
               • mossy fiber
               • Schaffer collaterals
           • inc in post-synap response because of prior stim from presyn
           • depolarization of post-syn cell simultaneously with input
           • associativity
             • weak synapse occurring w strong- weak shows LTP
             • dendritic spikes from strong stim
           • regular transmission vs. strong activation
             • AP causes glutamate release
             • EPSP
             • closed NMDA receptor because Mg ++ blocks opening
             • strong- more APs, more glutamate, more depolarization, Mg ++ displaced
               • Ca++ comes in and activates other pathways in postsynaptic cell
               • CaMKII activated
                 • production/release of retrograde messenger, increases NT released
                 • increases AMPA receptors, number or size of synapses
           • opposite is long-term depression/LTD
             • fewer AMPA receptors in post-synaptic cell
       • Aplysia
         • Kandel: habituation and sensitization in aplysia
         • apply to mammals too

4. amnesia

   • two types
     • retrograde- lose prior to event, recent mem especially
     • anterograde- after, can't learn new
   • linked brain regions
     • medial temporal lobes
       • hippocampus
       • amygdala
       • limbic cortex
     • diencephalon
       • thalamus
       • hypothalamus
     • others
   • human models for memory
     • HM
       • epilepsy surgery
       • mild retrograde/severe anterograde loss
       • had short-term
       • can't form long term after surgery
         • declarative deficiency
           • episodes
           • new facts
         • can form implicit memories
         • can be classically and instrumentally conditioned
       • lost 1/3 hippocampus
       • also lost lots of entorhinal cortex, most of parahippocampal cortex, some amygdala, parts of temporal
     • NA and BJ
       • slight retrograde memory, severe anterograde
       • left medial dorsal thalamus/mammillary body damage
       • no HI damage
     • Clive Wearing
       • encephalitis
       • bilateral loss of temporal lobes
       • anterograde and retrograde amnesia
     • KC
       • motorcycle head injury
       • lateral temporal lobes spared
       • bilateral damage to hippocampus and parahippocamapl cortex, cerebral too
       • semantic memory spared
       • retro and anterograde amnesia
   • neurogenerative diseases
     • Alzheimers etc.
     • semantic dementia
       • anomia
       • episodic maintained
       • degeneration of lateral anterior temp lobe
   • human study conclusions
     • anterograde/retrograde mechanisms different
       • consolidating and recalling different
       • HI consolidates but does not store/is not involved in storage recall
       • cortex sight of storage/recall older memories
     • hippocampus needed for some memories, NOT short term
     • long-term memories
       • HI not needed for implicit memories
       • HI needed for explicit
         • intact HI may not preserve semantic memories
         • might not be needed for semantic memory
   • animal models for memory
     • animals- classical or instrumental conditioning
       • not like amnesiac studies
     • monkeys
       • bilateral MTL lesions
         • like HM (declarative)
       • delayed non-matching to sample
       • HI for temporary storage
     • rodents
       • place cells
         • HI cells fire in response to location
         • stable
         • represent formed spatial map?
         • change if environmental cues change
       • spatial memory
         • Morris water maze
           • platform location from spatial nav
           • HI can't learn spatial relation but can make single associations
   • overall conclusions about what HI does
     • tie experiences and stimuli together
       • can learn new w damage (implicit)
       • episodic needs time/space relation
     • learn sequences/order of multiple stimuli
       • NOT single associations
     • establish relations between stimuli
       • context- can affect performance if aware
       • HI damage- can't distinguish between contexts
     • reconsolidation of memory
       • reactivation of LTMs
       • blocking this results in LTM loss
       • proteins produced for this
         • drug blocking right after training- development of LTM prevented
       • can also disturb reconsolidation, in addition to consolidation