Multiple long-range projections convey position information to the agranular retrosplenial cortex

Area of Science:

• Neuroscience
• Systems Neuroscience
• Cognitive Neuroscience

Background:

• Neuronal signals encoding an animal's position are crucial for neocortical processing and are widely assumed to originate from the hippocampus.
• The precise origins of these spatial signals projecting to key navigation and memory circuits, like the retrosplenial cortex (RSC), remain largely uninvestigated.

Purpose of the Study:

• To identify the specific brain regions that provide positional information to the agranular retrosplenial cortex (RSC).
• To investigate the contribution of various long-range inputs to the RSC's spatial representation.

Main Methods:

• Utilized two-photon axonal imaging in head-fixed mice performing a spatial navigation task in darkness.
• Comprehensively characterized long-range inputs to the agranular RSC.

Main Results:

• Most long-range pathways projecting to the RSC carry spatial position information, but with significant variations in signal strength.
• Axons from the secondary motor cortex and posterior parietal cortex were found to transmit the most significant position information.
• In contrast, inputs from the anterior cingulate cortex, orbitofrontal cortex, and thalamus conveyed substantially less spatial information, while visual cortex inputs were negligible.

Conclusions:

• The hippocampus is not the sole source of positional information for the RSC.
• The RSC functions as a central hub within a distributed neural network that shares spatial position information across multiple brain areas.
• This highlights a broader network involved in spatial cognition beyond hippocampal-centric models.