Modular Network between Postrhinal Visual Cortex, Amygdala, and Entorhinal Cortex | JoVE Visualize

Area of Science:

Neuroscience
Visual Cortex Function
Spatial Navigation

Background:

The postrhinal cortex (POR) integrates spatial and nonspatial visual information.
It is implicated in landmark navigation influenced by amygdala's affective input.
POR contains muscarinic acetylcholine receptor 2 (M2)-positive (M2+) and M2-negative (M2-) modules involved in sensory integration.

Purpose of the Study:

To investigate the specific circuits within POR modules that integrate visual, affective, and navigational information.
To determine how thalamic, cortical, and amygdalar inputs are processed within M2+ and M2- modules of POR.
To elucidate the pathways from POR to the entorhinal cortex involved in landmark-based navigation.

Main Methods:

Utilized anterograde and retrograde labeling techniques with conventional and viral tracers in male and female mice.
Examined projections from higher visual areas, primary visual cortex, and dorsal stream areas to the amygdala.
Mapped inputs from the dorsal lateral geniculate nucleus and lateral posterior nucleus to specific layers and M2 modules of POR.
Investigated amygdalar inputs to POR and their overlap with neuronal dendrites projecting to the entorhinal cortex.

Main Results:

Higher visual areas of the ventral cortical stream project to the amygdala; primary visual cortex and dorsal stream areas do not.
Thalamic inputs (dorsal lateral geniculate nucleus, lateral posterior nucleus) to POR layer 1 (L1) were spatially clustered and targeted M2+ patches.
Amygdalar input to POR L1 targeted M2- interpatches, overlapping with apical dendrites of POR neurons projecting to the amygdala and entorhinal area lateral, medial (ENTm).
Subnetworks for spatial mapping in POR do not receive direct M2+ thalamocortical inputs but involve M2- interpatches influenced by the amygdala.

Conclusions:

The POR is organized into distinct modules receiving specific inputs, suggesting a division of labor in processing visual and affective information.
Spatial mapping subnetworks in POR rely on local M2- interpatch networks, modulated by amygdalar affective input, rather than direct M2+ thalamocortical inputs.
This processing stream, involving M2- interpatches and projecting to ENTm, likely assigns emotional salience to visual landmarks, guiding goal-directed navigation.