Hippocampal Place Cells and the Rapid Learning of Spatiotemporal Sequences

The University Of Texas Health Science Center At Houston, Houston TX

Investigators

Abstract

A fundamental challenge in psychology and cognitive neuroscience is to understand the brain mechanisms that underlie the ability to learn and remember new information. A brain structure called the hippocampus has been at the forefront of research into this question for many years. People with damage to the hippocampus lose the ability to form lasting memories about the events they experience in everyday life (this type of memory is called "episodic memory"). Such memories require a mechanism that can rapidly link together the sequence of events that occurs in an episode and store this sequence in memory. This project will investigate this mechanism by recording the electrical activity of large populations of brain cells (neurons) in the hippocampus of the rat. Hippocampal neurons are selectively active when the rat occupies restricted locations in the environment. The activity of these "place cells" is thought to represent the rat's mental map of its environment (similar properties have been found in the hippocampus of humans). As the rat moves through the environment, its memory of the routes it has taken is encoded in the connections between the place cells that are activated in sequence along the route. It is hypothesized that the place cells of the CA3 subregion of the hippocampus will rapidly acquire this sequence information in a new environment, in order to rapidly create new memories of its movements in the environment. As the rat explores the environment and learns the location of food sources, it is hypothesized that these memories will create a navigational map that allows the rat to move directly to the hidden food source from any arbitrary location. These experiments will illuminate some of the basic mechanisms by which the brain stores the sequences of spatiotemporal events that underlie our memories of past events. This project will offer training opportunities for post-doctoral fellows, and the Dr. Knierim intends to keep reporting his findings to the public during interviews on public radio.