Functional connectivity in rat brain at 200 μm resolution.

Area of Science:

• Neuroscience
• Neuroimaging
• Somatosensory System

Background:

• Understanding the brain's response to sensory input is crucial for neuroscience.
• Functional magnetic resonance imaging (fMRI) allows non-invasive visualization of brain activity.

Purpose of the Study:

• To investigate the somatosensory fMRI response to electrical stimulation of a rat's digit.
• To map functional connectivity within the rat sensorimotor cortex at high resolution.

Main Methods:

• Utilized high-resolution (200 μm cubic) 9.4 T fMRI in four rats.
• Applied electrical stimulation to the middle phalange of the second digit.
• Employed functional connectivity fMRI (fcMRI) to analyze voxel interdependencies.

Main Results:

• High-threshold activation localized to a penetrating vein and a single cortical column in the forepaw barrel subfield (FBS).
• Robust activation observed in the indusium griseum (IG).
• Decreasing thresholds revealed spreading connectivity to S2, M1/M2, and contralateral S1 areas, indicating complex patterns potentially involving association fibers.

Conclusions:

• High-resolution fMRI successfully mapped somatosensory responses and functional connectivity in the rat brain.
• The study highlights complex connectivity patterns within the sensorimotor cortex, with S2 and IG showing extensive and regionally varied connections.
• Observed connectivity beyond the typical region of sensitivity suggests an extended volume of observable tissue.