Amnesia

							Retrograde Amnesia:
Is Memory Gone For Good
    Or Just Hiding Out?


Gretchen Hanson Gotthard, Ph.D.
   Randolph-Macon Woman’s College
            Lynchburg, VA
Hypothetical Memory Processes

Encoding       Storage   Retrieval


 Forgetting
 Amnesia
What Causes Amnesia?
   Transient Agents:
     Electroconvulsive Shock
      (ECS)
     Hypothermia

     Hyperthermia

     Concussive Head Injury

   Permanent Agents:
     Stroke
     Brain Tumor

     Brain Lesion
Two Types of Amnesia
1.   Anterograde Amnesia:
      new information

        “Memento” and H.M.

2.   Retrograde Amnesia:
      old information

        Trevor Reece Jones



       Retrograde Amnesia     Anterograde Amnesia
Temporal Gradient
of Retrograde Amnesia
                                                       Normal Memory      Amnesia

   Normal Memory                              100

       Recent better than                      80



                             Percent Correct
        Remote                                  60
   Amnesia                                     40
       Remote better than                      20
        Recent
                                                 0
                                                     Recent                Remote
                                                          Time From Learning
Consolidation Theory
   Müller and Pilzecker (1900)
     Storage of information is disrupted.

       Permanent loss of memory.



    Encoding   X    Storage         Retrieval
Evidence for Consolidation Theory
   Duncan (1949)
     Passive avoidance

     ECS or No ECS
      (varying delays)
     Tested 24 hours
      later
Results
                                                        No ECS
                                                        ECS
                        16
                        14
      Mean Avoidances

                        12
                        10
                         8
                         6
                         4
                         2
                         0
                             0.3 0.6   1    4   15     60 240 840

                             Delay Between Learning and ECS
                                           (seconds)
Retrieval Failure Theory

   Spear and Riccio (1994) and others…
     Retrieval is disrupted

       Temporary loss of memory




Encoding          Storage   X     Retrieval
Evidence for Retrieval Failure Theory
   Delayed Onset of
    Retrograde Amnesia
       Geller and Jarvik
        (1968)
          Passive avoidance

          ECS or No ECS
           (immediately after
           training)
          Tested 1, 2, 6, and

           24 hours later
Results
                                               No ECS       ECS
      Latency to Cross (seconds)
                                   300
                                   250
                                   200
                                   150
                                   100
                                    50
                                     0
                                         1 hr 2 hr 6 hr 24 hr
                                               Test Delay
More Delayed Onset of
Retrograde Amnesia
   Lynch and Yarnell (1973)
     Football players

     Questioned players

      immediately and at
      delays
     Experimental Group

     Control Group
Results
                              No Concussion    Concussion

                            100
          Percent Correct
                             80
                             60
                             40
                             20
                              0
                                  30     5     10     20
                                  sec   min    min    min
                                         Test Delay
More Evidence for Retrieval Failure
   Reminder Treatment Effects
     Hinderliter, Webster, and Riccio (1975)

         Passive avoidance
         Hypothermia (immediately after training)
         Reminder or no reminder (prior to testing)
Results
                                   700

      Latency to Cross (seconds)   600

                                   500

                                   400

                                   300

                                   200

                                   100

                                     0
                                           Hypo/   Hypo/   No
                                         No Remind Remind Hypo
How do reminder treatments work?

   “Two Bump” Theory
     Washington Post Story
      (early 1990’s)
     Levy (1987)

   State Dependent Retention
More Reminder Treatment Effects

   Hanson, Bunsey,
    and Riccio (2002)
      Two odor

       discriminations
       (Bunsey Digging
       Task)
Surgery
    Lesions to either:
1.   Hippocampal Formation
     (HF)
        Episodic Memory
         (Events)
2.   Parahippocampal Region
     (PR)
        Semantic Memory
         (Facts)              Parahippocampal
                                  Region
Hippocampal Formation:
Episodic Memory (events)
Parahippocampal Region:
Semantic Memory (facts)
Testing

   Two probe trials
    (no FL in cups)
   First probe trial:
    reminder treatment
    for second probe trial
Results: Latency to Dig
                           140
                           120
       Latency (seconds)
                           100
                            80
                            60
                            40
                            20
                             0
                                 HF     PR      CON
                                      Disc. 1   Disc. 2
Results: Choice
                  1

                 0.8

                 0.6
        Choice



                 0.4

                 0.2

                  0
                       HF     PR      CON

                            Disc. 1    Disc. 2
     So Is Memory Gone For Good,
           Or Just Hiding Out?
   It’s probably “Just Hiding Out”:
      Consolidation Theory: memories should be

       immediately and permanently gone
       However…
        Delayed Onset of Amnesia
        Reminder Treatment Effects

   Retrieval Failure Theory provides a better
    explanation.
       Current Research: Sand Maze
   Sand Maze: appetitive
    version of Morris Water
    Maze
   Hippocampal Formation:
    important for spatial
    learning and memory
   WIN-2 study: synthetic
    cannabinoids and state
    dependent retention
      Ashley Smith