An examination of the relationship between frontal and posterior parietal neocortical transcallosal evoked field potentials, long-term potentiation, water maze performance, and environmental enrichment in the rat

In this thesis several experiments were conducted to test the hypothesis that transcallosal evoked field potentials (TCEP) in the frontal cortex (FC) and posterior parietal cortex (PPC) undergo electrophysiological change as a result of water maze (WM) spatial training or environmental enrichment (EE). In Chapter 2 (Beiko and Cain, 1998), a single experiment was conducted in which 10 days of WM spatial training was administered to rats with chronically implanted PPC electrodes. Assessment of the TCEP profile was made 1 and 23 hours after each training session. The data showed that WM training was not associated with detectable changes in the PPC TCEPs, despite the occurrence of robust spatial learning. In Chapter 3, several experiments were conducted to examine the relationship between WM training and EE on the TCEP in both the FC and the PPC. Experiment one used a between subject design to monitor the TCEP in animals that received either prolonged EE or continued homecage (HC) dwelling. The results showed that EE was associated with an increase in the amplitude of the monosynaptic component of the TCEP in the PPC, but not in the FC. Experiment two compared animals that received EE with animals that remained in their HC on WM spatial performance and the TCEP. The results showed that the EE animals had better WM performance and larger TCEP components than the HC animals. Experiment three used a within subject design to monitor the TCEP in animals that received EE or continued HC dwelling. The results showed no significant effect of EE on the TCEP in either the FC or PPC. A surprising finding was that the HC animals produced more LTP after tetanization than the EE animals. The series of experiments presented in this thesis greatly extend the research on LTP and learning and memory by: (1) examining the neocortex as opposed to the hippocampus and (2) employing different behavioural manipulations coupled with detailed behavioural analyses. The results are discussed in the context of changes that should be expected to occur in a neocortical field potential following these behavioural manipulations.