Why do we explore nearby areas before venturing out to farther ones? New eLife paper in the Brecht lab
Berlin scientists now show that the medial entorhinal cortex, which is important for spatial memory matures from the top- representing nearby areas, to the bottom- which represents areas farther away.
Many animals, from rats to humans, need to navigate their environments to find food or shelter. This ability relies on a kind of memory known as spatial memory, which provides a map of the outside world within the animal’s brain. Specifically, cells in a part of the brain called the medial entorhinal cortex act like the grids present on a map, and are known as grid cells. Other cells in this region represent boundaries in the environment and are known as border cells. These cells and other cells connect to each other to make the spatial memory circuit.
Previous research had reported that the grid cells were not present in the very early stages of an animal’s life. It was also not clear how the different cell types involved in spatial memory develop after birth. Ray and Brecht have now studied rats and found that certain characteristic structures in the circuit are present at birth. For example, cells that were most likely to become grid cells, were already laid out in a grid, indicating that this layout is instructed by genetic information rather than experience.
Ray and Brecht also found that the cells that most likely become grid cells matured later than the cells that most likely become border cells. Further analysis then revealed that the circuits in the top part of the medial entorhinal cortex, which represents nearby areas, matured earlier than those in the bottom part of this region, which represent farther areas. These findings could therefore explain why rats explore nearby areas earlier in life before going on to explore further away areas at later stages.
More work is needed to characterize other components of the neural circuits involved in spatial memory to provide a complete understanding of how these memories are formed. Future experiments could also ask if encouraging young rats to explore a wider area can cause the circuits to mature more quickly.
Contact:
Saikat Ray, Prof. Dr. Michael Brecht
Bernstein Center for Computational Neuroscience Berlin
Humboldt-Universität zu Berlin
Philippstr. 13, House 6
10115 Berlin
Tel: +49 (0)30 2093 6770
Email: saikat.ray@bccn-berlin.de, michael.brecht@bccn-berlin.de
Adapted from eLife Digest for:
- Ray & M. Brecht (2016) Structural development and dorsoventral maturation of the medial entorhinal cortex. eLife 5, e13343. DOI: 10.7554/eLife.13343