Modular horizontal network within mouse primary visual cortex

Area of Science:

• Neuroscience
• Visual Cortex Research
• Computational Neuroscience

Background:

• Feedback connections from higher cortical areas and local horizontal connections in primary visual cortex (V1) are crucial for contextual processing.
• Layer 1 (L1) of V1 integrates feedback and local inputs onto projection neuron dendrites, linking external stimuli with internal information.

Purpose of the Study:

• To investigate the overlap and interaction of feedback and local horizontal connections within Layer 1 of the mouse primary visual cortex (V1).
• To elucidate the role of these interactions in processing visual information related to object and self-motion.

Main Methods:

• Utilized anterograde and retrograde viral tracers to map local horizontal connections within mouse V1.
• Characterized the distribution and termination patterns of long-range horizontal connections, identifying M2 muscarinic acetylcholine receptor-negative (M2-) interpatches.
• Examined the overlap of these connections with apical dendrites of L2/3 and L5 projection neurons in L1.

Main Results:

• Identified two types of local horizontal connections: short, image-point-specific connections, and long, patchy connections extending into the receptive field surround.
• Long horizontal connections preferentially terminated in M2-interpatches.
• Overlapping inputs from feedback networks (LP thalamus, medial dorsal stream) and local horizontal connections were observed in M2-interpatches with apical dendrites, forming module-selective loops.

Conclusions:

• Layer 1 (L1) of the primary visual cortex (V1) contains distinct M2-interpatches where local and feedback inputs converge.
• These M2-interpatches facilitate interactions between topographically distant visual representations, suggesting a role in integrating contextual information.
• The findings indicate that interactions within M2-interpatches are critical for processing visual inputs related to object and self-motion.