|M.Sc Student||Telhami Gadir|
|Subject||Electrophysiological Recordings of Grid Cells in a|
|Department||Department of Medicine||Supervisor||Professor Dori Derdikman|
|Full Thesis text|
The hippocampus and adjacent regions contain several types of neurons whose firing activity is correlated with an animal's position and orientation in space, such as place cells, neurons in the hippocampus that fire whenever the animal moves through a specific location within its environment, and grid cells, neurons in medial entorhinal cortex, which fire in a precise pattern in the environment. These firing fields form a periodic hexagonal array. The relationship between grid orientation and spatial behavior remains largely unknown. In contrast, spatial behavior studies have demonstrated a clear link between environmental geometry and the ability of animals to stay oriented during a goal directed task. Specifically, when a rat is placed in a rectangular arena and trained to seek food in one corner and then disoriented, it often confuses between the correct corner and an opposite corner that is geometrically identical. This type of error is referred to as a "rotational" error. This behavior has been argued to represent ability for geometry perception. The best candidates for the role of perceiving global environmental characteristics such as geometry are grid cells.
In this study we set out to establish a behavioral context in which to examine the correlation between spatial behavior in a goal-directed task, and the orientation of grid cells. We focused on the spatial firing rate map of grid cells in correct and rotational corner choices, and the correlation to a random spatial behavior in an oriented context within the same environment. We found, that when the rats were oriented, the grid orientation persisted while when the rats were disoriented, the grid rotated by 180 degrees, corresponding with a rotational error in spatial behavior. The results signify the first time that grid cell activity was demonstrated to have a clear connection to behavior, and to facilitating orientation in space rather than just tracking of position.