Short Term Retrograde Amnesia in Rats

1
Short Term Retrograde Amnesia in Rats

• Stephan Chorover
• Peter Schiller
• 1965

2
Background

• Electroconvulsive shock (ECS) has previously been
  linked to impaired performance of learned
  responses in rats
• Majority of impairment is found to vary inversely
  with the time interval between learning and ECS
  treatment.
• Question Is this impairment due to Retrograde
  Amnesia (memory interference) or conflict and
  competing conditioned responses

3
Method

• 477 male rats aged 75-100 days old tested
• Rats were housed in pairs in standard wire cages
• The Box was a 40cm square compartment with
  walls 30cm high. The floor was made of stainless
  steel rods that were connected to voltage shock
  was given when both rats feet were on the rods
• Platform 13cm square in center of the box

4
Procedure

• The normal response of the rats was to step down
  of the platform relatively quickly to explore
• Baseline data for step-down time was measured
  over the course of three days (one trial per
  day). At the start of each of these trials rat
  was placed on platform and time score was
  recorded. Average time was 1.6 seconds
• Ten seconds after stepping down, rat was removed
• After trial on day 3, ear snaps were surgically
  implanted on rats ears (similar to clamps on
  jumper cables)
• Rats were assigned to 2 groups, plus some
  controls, for test phase (days 5-8)

5
Groups

• Group 1 Foot Shock
• - Split into four subgroups received foot shock
  of .5, 1, 2, or 4 seconds.
• Group 2 Foot and Ear Shock
• - Split into five subgroups each receiving first
  the foot shock than the ear shock for .5, 2, 5,
  10, or 30 seconds

6
Single Trial Results

• Foot Shock Only Group - Step down Time Averaged
  4 Seconds (Intervals had only weak influence on
  avoidance)
• Foot and ECS - Avoidance of the grid increased as
  the time between the foot and ear shock
  increased. After 30 seconds, results between two
  groups showed no significant difference

7
Single Treatment Results By Group
8
Results after Three Trials

• Foot Only Group showed little overall change in
  level of avoidance
• Foot and Ear Shock Group again showed an
  increased avoidance of grid as time between two
  shocks increased.

9
What Does This Mean?

• ECS shock followed shortly after avoidance
  training trials may impair subjects retention
• Length of latency between the first shock and ECS
  shock determines the amount of impairment.
• ECS shock could affect memory depending on when
  it is administered.