This task asseses a rat’s ability to remember the fixed location of a hidden escape platform in a water-maze. The top of the platform is 2 cm below the level of the opaque pool water, so the rat cannot see it, but it can learn its location relative to extra-maze cues. The rat is placed into the pool at different starting locations on successive trials. Dependent measures include latency to find the platform on each trial, and time spent swimming in the area of the platform on probe trials with the platform removed from the pool. This task assesses spatial reference memory.

The DMTP task assesses a rat’s ability to retain, over various delays, information about where it recently found the hidden platform, on a single occasion. During the sample phase of each trial, the rat searches for and finds the hidden platform. After a delay, the rat is returned to the pool and allowed to find the platform again in the same location. Decreased escape latency from the first swim to the second swim reflects the extent to which the rat remembers the platform location. The location of the platform, and thus the correct place information, changes on each trail. This task places a heavy demand on working-memory.

The rat is familiarized with two identical objects in the circular open field for a designated amount of time over consecutive days. Following a delay, the rat is placed back into the apparatus for the test phase. On the test phase, one object remains in the same location while the other object is moved to a new location within the circular open field. We measure 1) the amount of time spent exploring the displaced object versus the non-displaced object, 2) the amount of time spent in the quadrant where the object was displaced to versus the quadrant containing the non-displaced object and 3) the amount of time spent in the quadrant that previously contained the displaced object versus the quadrant that was previously empty and remained empty for the test. We have found that control animals express the memory for the spatial location of objects in several ways.

The maze consists of 8 equally sized elevated arms that extend from a center platform. At the entrance of each arm there is a clear divider door and located at the end of each arm is a food well. Many versions of this task have been developed and the one commonly used in our lab consists of placing the rat in the center of the apparatus with four randomly selected doors open. Once the rat retrieves the pellets from the end of the four arms, the remaining doors are opened. The dependent measure is the number of times the rat enters a previously visited arm. The trial is completed once all pellets are collected.