Y-Maze
Behavioral Task
Aversive Y-maze
Discrimination Task
The animals
in this experiment are givenone training trial per day for 6 consecutive
days. Training begins by placing each animal in the stem of the Y-maze.
The animals are then given up to 5 minutes to locate and consume 10 pellets
(45mg each) placed in a food cup on the rear wall of the right alley and
5 pellets placed in the food cup at the very end of the left alley. A
trial ends when all 15 of the food pellets are retrieved and consumed
in the maze. The animals are then allowed to freely explore the alleys
for an additional 20 s before being returned to their home cages. Digital
timers are used to record a) the initial latency to enter either alley
at the start of training b) the seconds spent in each alley before all
pellets were consummed c) the seconds spent in an alley after pellets
were consummed d) the cumulative latency to consume all pellets from the
beginning of a trial and e) the time spent in the non-baited stem or start
alley of the y-maze.
On Day 6 of training, the cardboard insert covering the floor of the maze
is removed from only the right alley to expose the stainless steel footshock
plates. As in the previous days of training, each animal was allowed to
consume all of the food pellets placed in the left and right alley. However,
when the subject returns to the right alley and approaches the empty food
cup, a mild footsh ock is administered for 0.5 seconds in that alley.
Immediately after the footshock, the animal is removed from the maze and
randomly assigned to a drug treatment group.
Retention of the footshock training is assessed on Day 7 and 8 under
two separate conditions. The latency to enter the right alley and the
number of seconds to consume all of the pellets in the right alley where
footshock was received during training serves as indices of retention
on both tests. On the first retention test, the cardboard insert is returned
to the right alley as during the first 5 days of training. Thus, the stainless
steel plates from which footshock was delivered on day 6 are concealed
from the animals on this retention test. This manipulation provides an
assesment of the animals memory of the footshock training in the absence
of the most salient contextual cue associated with the footshock (i.e.
the stainless steel footshock plates). During the second retention test
given on Day 8, the cardboard insert in the right alley is removed to
expose the stainless steel plates. On this day, the animals are exposed
to identical contextual cues that were present on the day of footshock
training. The two different tests are expected to reveal whether a) memory
for an emotional experience is facilitated by specific pharmacological
agents under normal testing conditions and b) to assess whether these
treatments affect retention under conditions in which memory is weakened
by removing salient cues that are linked or associated with an arousing
event such as footshock.
Appetitive
Y-Maze Light-Dark Discrimination Task
During training each animal is given 25 light-dark discrimination trials
on Day 1 and an additional 10 training trials on Day 2. For Trial 1 on
each day of training and on the subsequent retention tests, subjects are
placed in the stem of the maze facing the rear wall with the cue light
off in that arm and the door raised. Once the door is lowered, the rats
are allowed to choose between a dark unbaited arm or an illuminated arm
baited with 3 sucrose pellets. After entering one of the arms, the door
is raised enclosing the rat in that choice section for a period of 10
seconds. A new arm is then baited and the back panel in that arm
illuminated. The next trial then begins by lowering the door and allowing
the animal to choose between the new dark unbaited arm or the illuminated
baited arm. After the 10 training trials on Day 2, each subject is removed
from the maze and given a drug treatment. Retention tests are given on
Days 4 and 9 and consisted of the same procedures that were used during
training (see below). Mean percentage of correct responses and number
of trials to reach 5 total correct responses serve as indices of retention.
Cedric
Williams
The University of Virginia
Psychology Department