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Brain-Wide Connectivity Patterns of Feedforward and Feedback Cortico-Cortical Neurons in the Mouse Secondary Visual
Richard G Dickson1, Matthew W Jacobs1, John M Ratliff1
1Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, California, USA.
The Journal of Comparative Neurology
|December 4, 2025
Summary
Feedforward (FF) and feedback (FB) neurons in the secondary visual cortex receive similar long-distance inputs. However, distinct proportions of inputs from specific cortical areas highlight functional differences between these neuron types.
Area of Science:
- Neuroscience
- Visual System
- Cortical Circuits
Background:
- Feedforward (FF) and feedback (FB) cortico-cortical neurons are distinct subtypes with specialized roles.
- Their differing functions suggest potential differences in presynaptic inputs, which remain largely uncharacterized.
Purpose of the Study:
- To map and compare the brain-wide, long-distance presynaptic inputs to FF and FB neuron types in the secondary visual cortex (VISl).
- To understand how input connectivity supports the distinct functions of these neuronal populations.
Main Methods:
- Utilized projection- and layer-specific monosynaptic rabies tracing techniques.
- Mapped inputs to FF and FB neuron subtypes within the VISl (secondary visual cortex) of the mouse brain.
Main Results:
- Both FF and FB neurons predominantly received inputs from the primary visual cortex (VISp) and other visual areas.
- Significant differences were observed in the proportion of inputs from specific visual, retrosplenial, and auditory cortices between FF and FB types.
Conclusions:
- FF and FB neurons in VISl share largely similar overall input patterns but differ in the proportional contribution of specific cortical inputs.
- These findings provide an anatomical basis for understanding the functional segregation and circuit integration of FF and FB neurons.
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