Types of Memory

Types of Memory

1. STM and LTM

   • Hebb (1949)
     • No one mech could acc for all phenomena of learning
     • STM
       • events that have just occurred
     • LTM
       • events from further back
   • STM stores 7 items without rehearsal
     • LTM vast capacity
   • STM depends on rehearsal
     • If reheard, chances of remembering it increases but if interrupted chances decrease
     • LTM things you haven't thought about in years
   • STM once forgotten it is lost
     • LTM with hints you can reconstruct something you thought you had forgotten
   • all info enters STM where it consolidates into LTM
     • if interrupted rehearsal before consolidating, info is lost

2. Changing Views of Consolidation

   • not all STM memos are temp stored before entering LTM
   • Original idea
     • brain held onto info in STM until synthesising new proteins to enter LTM
   • Stressful or emotionally exciting experiences increase the secretion of epinephrine and cortisol
     • small amounts of cortisol activate amygdala and hippocampus
       • They enhance the storage and consolidation of recent experiences
         • Amygdala in turn stimulates hippocampus and cerebral cortex
     • prolonged stress releases more cortisol which impairs memory
   • a memory re awakened by a reminder becomes labile - changeable or vulnerable
     • if reminder is followed by similar experience it's reconsolidated by process requiring protein synthesis
       • giving a reminder and then taking drug that blocks protein synthesis substantially weakens the memory
       • new experiences during the reconsolidating process can modify the memory

3. Working Memory

   • Baddeley & Hitch
   • delayed response task
     • requires responding to something that you saw or heard a short while ago
     • using delay, learner stores representation of stimulus
       • research points to prefrontal cortex as important location for this storage
     • during delay, certain cells in prefrontal cortex and parietal cortex increase activity
       • different cells become active depending on direction the eye movement will need to take
         • Chafee & Goldman-Rakic (1998)
     • increase in activity doesn't take form of repeated at ion potentials
       • cells store extra calcium, increasing their readiness to respond to new signals when the time comes
   • damage to prefrontal cortex impairs performance
     • deficit can be precise depending on exact location of damage
       • After damage to spot, monkey might be unable to remember that light had been directly to the left although they can see to the left find
   • older people have impairments of WM due to changes in prefrontal cortex
     • Studies on ages monkeys find decreases in number neurones and amount input in certain part soy prefrontal cortex
     • those with intact memory show greater activity than young adults
       • prefrontal cortex is working harder in older adults to compensate for impairments elsewhere in brain