Two major network domains in the dorsal raphe nucleus

Area of Science:

• Neuroscience
• Brain Connectivity
• Serotonergic Systems

Background:

• Serotonin neurons in the dorsal and median raphe nuclei (DR and MR) form heterogeneous clusters with organized forebrain projections.
• Defining distinct subgroups of serotonin neurons within these nuclei remains challenging.
• Functional distinctions in neurons necessitate participation in unique neural networks.

Purpose of the Study:

• To investigate the heterogeneity of serotonin neurons in the DR and MR.
• To define functional subgroups of serotonin neurons based on afferent input networks.
• To clarify the network organization of the DR and its relationship with the MR.

Main Methods:

• Analysis of subregions within the DR and MR based on afferent input.
• Application of clustering methods and principal component analysis.
• Utilizing anterograde tract-tracing data from the Allen Mouse Brain Connectivity Atlas in mice.

Main Results:

• A significant divergence in afferent innervation networks within the DR was identified.
• The caudal third of the DR exhibited greater similarity in afferent input to the MR compared to the rostral two-thirds of the DR.
• The rostral DR is linked to motor and motivated behavior networks, while the caudal DR is associated with hippocampal activity regulation.

Conclusions:

• The caudal DR represents a significant source of heterogeneity within the DR.
• The caudal DR's network properties align more closely with the MR.
• The caudal DR may be functionally considered a dorsal extension of the MR.