Constituents and functional implications of the rat default mode network

Area of Science:

• Neuroscience
• Comparative Neurology
• Brain Imaging

Background:

• The default mode network (DMN) is crucial for self-referential processing in humans.
• The DMN's functional organization, including its subsystems, is key to understanding brain hierarchy and segregation.
• Translational research in neuropsychiatric disorders benefits from preclinical models, yet the DMN's structure in nonhuman species remains uncharacterized.

Purpose of the Study:

• To identify and characterize the subcomponents of the rat default mode network (DMN).
• To investigate the anatomical and functional connectivity supporting the DMN's organization in rats.
• To establish a preclinical model for studying DMN function and dysfunction.

Main Methods:

• Resting-state functional MRI (rs-fMRI) was used to identify the DMN in rats.
• Independent-component analysis and modularity analyses were applied to rs-fMRI data for DMN fractionation.
• Diffusion tensor imaging (DTI) tractography was employed to examine anatomical connectivity within the DMN.

Main Results:

• The rat DMN was successfully identified and fractionated into anterior and posterior subsystems, further divided into five modules.
• DTI tractography revealed a strong correlation between fiber density and functional connectivity, supporting the identified DMN subsystems.
• Distinct modulations within and between DMN subcomponents were observed in a neurocognitive aging model.

Conclusions:

• The rat DMN exhibits a partitioned structure similar to the human DMN, with subcomponents potentially supporting distinct functions.
• These findings provide anatomical and functional evidence for DMN subsystems in rats, validating its use as a preclinical model.
• This study lays the groundwork for investigating the neurobiological mechanisms of DMN processing in normal and disease states using preclinical models.