Memory

Memory

1. Short Term Memory

   • Primary/active part of memory
     • Limited facility to store information
       • Memory Span
       • Roughly 7 items
       • Practice can improve this
         • "Chunking" items
           • Convert several pieces of info into one
             • Phone numbers
   • a.k.a. working memory
   • Lasts 15-30 seconds
     • Unless rehearsal or repition is involved
       • Rehearsal
         • Repeating information
           • Phone number
       • Distractions can reduce this facility
       • Repitition
         • Referred to as accoustic coding
         • may be out loud or 'in-your-head'
     • Short term memory decays or is deplaced rapidly

2. Long Term Memory

   • Unlimited capacity
     • Holds info not being used currently
   • Facts and skills are stored separately
   • Semantic code
     • Most long-term memory is stored and recalled as items related to their meaning

3. Localisation of memory in brain

   • The Limbic System
     • consists of several tissues involved in mediating emotional responses
       • Hippocampus
         • Involved in memory and learning

4. Encoding Memory

   • Hippocampus
     • transforms info into memory
     • Located in the left temporal lobe
     • Essential in encoding new memories
     • Shrunk in people with Alzheimer's
   • Refers to way individual transfers info to memory system
   • Accoustic encoding
     • Repeating phrase/fact
   • Mnemonics
   • Organisation of info into associated groups
   • Contextual cues
     • Due to association with previous event/smell/person/music etc.

5. Evidence for molecular basis for memory

   • New learning causes new synaptic connection & longer dendrites
   • Rehearsal & repition improve synaptic signals
   • When 2 signals reach synapse simultaneously
     • Easier for neurotransmitter to cross synapse later
       • e.g acetlycholine
   • Loss of acetlycholine-producing cells in limbic system of Alzheimer's sufferer
     • Evidence that acetlycholine involved in linking neurons to form memories
       • Connect illness characterised by memory loss to the loss of a chemical responsible for forming new memories
   • NMDA Receptors
     • Receptor molecule found in large quantities in post-synaptic membranes of neurons
     • Highly likely to be involved in forming memories
     • Unusual
       • 2 successive impulses needed to activate NMDA
         • Suggests it plays a role in memory storage

6. Transfer of information between short term and long term memory

   • Storage of memory is greatly enhanced by rehearsal
   • Serial Position Effect
     • Shown 20 items & try rememeber all
     • Initially
       • Use mnemonics etc to store info in LTM
     • Last few
       • remain in STM
     • Storage, & consequently, retrieval of mid-list items is haphazard
   • Retrieval
     • STM is fast and accurate
     • Failure of LTM
       • Due to inability to retrieve information
     • If facts are encoded in a structured way
       • Storage & retrieval are enhanced
       • Elaboration of meaning& contextual cues help

7. Encoding, storage and retrieval

   • The 2 stages in memorising
   • Common to short and long term memory