An electrophysiological study in freely exploring rats - Place cell properties and place field stability in the absence or presence of reward as a motivational factor.
Year: 2009
Type: dissertation
Abstract: The activity of pyramidal cells in the hippocampus can be spatially modulated. Numerous studies have been performed examining their properties, like what influences the position of their firing fields or what effect changes in the environment have. Most of these studies used reward to motivate the rat, keeping its activity level high, which is important for optimal recordings. In order to record single cell activity male Long Evans rats were implanted with four tetrodes, totalling 16 electrodes, in the CA1- region of the hippocampus. Three testing apparatuses were used. The first, a circular one, was used while we were searching for complex spike activity. The next two were square and identical except for the content, one was empty but the rat received a reward during the sessions, the other contained four objects and the rat did not receive a reward. Our aim was to compare the development and stability of the place fields in the presence and absence of reward. Place cell activity was only found in two of the rats implanted. One of these rats was tested in all three of the enclosures, and manipulations were made to the cues. For the other rat recordings were made in the circular apparatus and in the one containing objects, no cue manipulations were made. We found stable place fields in the presence and absence of reward. The firing fields appeared to be better defined when objects were present than in the empty enclosure where reward was given. The presence of objects in a testing enclosure affected the behaviour of the subjects. The activity level was just as high in reward and non-reward conditions, however the behaviour pattern differed. Rotating the cue card placed on the wall of the enclosure showed that other cues than this card were available to the rat. Due to our limited amount of data it is difficult to draw any conclusions. It is however clear that with the conditions used in this study stable place fields developed in the presence and absence of reward.
Author: Susanne Søgnen
Language: English
Topic: Memory and Neural Mechanisms
Subfield: Cognitive Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W1130024904