Friday, November 11, 2011

T-maze alternation in the rodent

In paper citation: (Deacon & Rawlins, 2006).

Introduction: T-mazes provide a valid way to study the working memory and hippocampal function of an animal, especially rats.

  • Spontaneous alteration: When two trials are given in quick succession, the rat spontaneously chooses the arm not visited before. 
  • Rewarded alteration: Reinforcing the rat's spontaneous alteration with a food reward.
  • Typical spontaneous alternation rates are around 75%.
Working memory vs. Reference memory:
  • A working memory task involves the rat remembering what he has just done (i.e. altering between sides of the T-maze). 
  • A reference memory task involves learning a rule that does not change (i.e. run down the white side of the maze) regardless of whether it is left or right.
  •  A rat learns reference memories in about 40 trials. 
  • Rats naturally alternate, and can be given food rewards for alternation.
  • Detects more subtle changes than the Morris Water Maze.
T-maze vs. Y-maze:
  • T-maze has discrete trials. Y-maze has continuous trials.
  • T-maze has less variance in trial time. Y-maze has more variance in trial time.
  • T-maze has more human interference/animal handling. Y-maze has no human interference/animal handling.
  • Alternation rates are lower in the Y maze (~65%).
  • Rats with hippocampus removed adopt side preferences, and will still score highly in a continuous trials procedure.