Entorhinal cortex represents task-relevant remote locations independently of CA1

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Spatial Navigation

Background:

• Neurons in the medial entorhinal cortex (MEC) are known to encode an animal's location during movement.
• However, the function of MEC neural representations during periods of immobility remains largely unexplored.
• Existing research suggests remote neural representations can support learning and reflect learned associations.

Purpose of the Study:

• To investigate the nature of medial entorhinal cortex (MEC) neural representations during immobility.
• To determine if MEC neurons exhibit nonlocal coding (representing locations other than the animal's current position) during immobility.
• To explore the relationship between MEC nonlocal coding, learning associations, and the CA1 region.

Main Methods:

• Simultaneous recording of hundreds of neurons in the MEC and CA1 regions of mice.
• Mice were trained to associate pairs of rewarded locations.
• Analysis of neural population activity during both movement and immobility, with and without sharp-wave ripples.

Main Results:

• MEC neural populations frequently engaged in nonlocal coding during immobility, representing distant locations.
• Cells with spatial firing fields at remote locations were identified as drivers of this nonlocal coding.
• Nonlocal coding occurred more often outside of sharp-wave ripples and showed less coordination with CA1 activity compared to previous findings.
• Remote task-relevant locations were preferentially represented during nonlocal coding at appropriate times.

Conclusions:

• MEC nonlocal coding during immobility is a prevalent phenomenon, distinct from its role during sharp-wave ripples.
• This nonlocal representation may serve to strengthen associations between learned locations independently of the CA1 region.
• MEC's capacity for nonlocal coding during immobility highlights its potential role in associative learning and memory consolidation.