EXPRESSION OF THE IMMEDIATE EARLY GENE ARC WHILE RUNNING ON A WHEEL IS SIMILAR TO WHEN EXPLORING A SPATIAL ENVIRONMENT.

picture of Ingrique Salt presenting his/her poster: EXPRESSION OF THE IMMEDIATE EARLY GENE ARC WHILE RUNNING ON A WHEEL IS SIMILAR TO WHEN EXPLORING A SPATIAL ENVIRONMENT.

Ingrique Salt , Sabhya Kumar, Jim Lester

EXPRESSION OF THE IMMEDIATE EARLY GENE ARC WHILE RUNNING ON A WHEEL IS SIMILAR TO WHEN EXPLORING A SPATIAL ENVIRONMENT.

The mammalian hippocampus is crucially involved in memory and spatial navigation. Neurons across the hippocampus show environmentally specific firing preferences; i.e.: these neurons fire in specific parts of the environment. The sum activity of these neurons is thought to form the basis for a cognitive map. Consequently, it may be predicted that when an animal is stationary in an environment, only a small number of place cells are activated compared to a rat exploring a large environment. Alternatively, the rodent may be evaluating the distance run on a track, analogous to a process of imaging oneself traveling along a track. In this second scenario we would expect a larger number of cells to be activated depending on the number of laps between rewards. To estimate the size of hippocampal CA1 networks involved in these different states, we utilized a technique known as cellular compartment analysis of Fluorescence in situ hybridization (catFISH). This technique can quantify the number of neurons active during a behavioral epoch. Studies using this technique have shown that when rodents freely explore an environment, approximately 40% of neurons in the CA1 region of the hippocampus are activated (Guzowski 1999). To test whether animals actively tracked the spatial distance between rewards we designed several inter-related experiments. First we predicted that if rats receive a randomly spaced (i.e. a random number of laps) food reward, only neurons whose activity was correlated with the rodent’s current location in its box would be activated. Second, we trained rodents to run for a fixed number of laps between rewards (e.g., every 5 laps, every 10 laps, etc). In this second condition, we predicted that if rodents were “mentally travelling a long a track”, then there should exist a linear increase in the number of active neurons. This work was support by the McKnight Brain Research Foundation and NIA grant AG012609.

Conference Home | List of Abstracts | Photo Gallery