Fragmentation of grid cell maps in a multicompartment environment.

Area of Science:

• Neuroscience
• Cognitive Science
• Spatial Cognition

Background:

• The entorhinal cortex and hippocampus are crucial for spatial memory and navigation.
• Grid cells and place cells are key neuronal populations involved in representing spatial environments.

Purpose of the Study:

• To investigate whether spatial representations in the entorhinal cortex are continuous or fragmented.
• To determine if environmental geometry influences the structure of neural maps.

Main Methods:

• Neural activity of grid cells was recorded in rats navigating a complex hairpin maze.
• The correlation of neural activity at different locations was analyzed.
• Behavioral experiments controlled for environmental structure versus stereotyped movement.

Main Results:

• Grid cell firing fields showed repeating submaps across compartments with similar directional running.
• Neural activity was least correlated at transitions between maze arms, indicating map fragmentation.
• Similar discontinuities were observed in hippocampal place cells.
• Fragmentation was absent in environments lacking internal walls, ruling out stereotyped behavior as the sole cause.

Conclusions:

• Spatial environments are represented as a mosaic of discrete submaps in the entorhinal cortex and hippocampus.
• These submaps correspond to the geometric structure of the environment.
• The brain divides spatial information into distinct, repeating units rather than a continuous representation.