Dissociable memory effects after medial thalamus lesions in the rat

In the past lectures, we've learned that the thalamus is a pretty important part of the brain, made up of smaller regions, where each region has its own function. The main roles function of the thalamus is to relay information coming in through the senses to where it’s supposed to go. We also discussed memory, and by extension memory loss in the brain. We learned that memory is not just recalling facts, but is made up of different areas and processes in the brain. The reason I picked this survey is because I was curious to see that, if the thalamus is as important to cognitive functions as indicated, what happens when the thalamus is hampered, and which specific areas in the thalamus contribute to memory loss.
             The current study looked at memory loss due to damage to three different areas within the thalamus. These three areas are called the lateral thalamic aggregate, the anterior thalamic aggregate, the posteromedial thalamic aggregate. The researchers felt that damage to these three areas would hamper memory, and that each would provide a different type of memory loss, due to the fact that each region connects to different parts of the brain (i.e. the anterior thalamic aggregate has connections with the hippocampus). The subjects (rats) were grouped into fours for each of the four tests, and were allowed to bar press for food. Each group of rats went into surgery, the first three having one of the three thalamic regions removed. The fourth group went into surgery but didn’t have any of the three parts removed. After surgery and recovery, the rats were placed into a series of tests.
            The tests including temporal order test, object familiarity, spatial memory, and reward magnitude. The spatial test was a maze that the rats had been familiar with before the surgery, and after surgery they were required to go back through again. The reward magnitude came next. In the reward magnitude the researchers utilized three types of cereal (maximize, fruit loops, and cocoa pops). The rats were allowed to run into the next room over and if they found maximize, when they ran back they would receive additional food in the form of cocoa pops. If the rat discovered fruit loops in the next room no additional food was given. The temporal test was simply that rats were exposed to novel objects in a set order (object A, a delay, and then object B) in an empty room. After a day, these same rats were placed in the same room with the objects given earlier in the room. The rats were observed to see that they went to the objects in the order that they were given the previous day. In the last test, the object familiarity test, the rats were exposed to a novel object and then became familiar with it. The next day these rats were placed in a room with a triplicate of the object from the previous day plus one more object that was not like the rest of the objects. Rats normally had a preference for the fourth object showing that they remembered the object previously discovered the day before.
           In the spatial test, the group with lesions to their anterior thalamic aggregate took less time in making decisions that the rest of the groups. The posteromedial thalamic group had more issues in conditioning to the reward magnitude test of any other group. In the temporal test, the anterior aggregate lesion group and the control group performed well by preferring the first of the two objects, and the posteromedial and lateral thalamic aggregate lesion groups did poorly. All groups did well on the object recognition test.