Functional Brain Imaging in the Mouse

Functional magnetic brain imaging (fMRI) provides a new tool for understanding the brain in humans. It is already been helpful in understanding connectivity and focal brain region functions across a variety of domains, i.e. vision, hearing, motor function, somatic sensation and emotional processing. However, functional brain imaging in the mouse model has trailed structural brain imaging development. 

• So why would fMRI be a potentially useful research tool in mice? There are several reasons. Here are some of the key reasons: 
• Mice are easily available and can be repeatedly scanned across time
• Molecular and genetic alterations are available that can perturb (modify) cellular and genetic systems related to brain development and brain function--looking at the fMRI effects of these perturbations would be helpful
• Mouse models are available for a variety of human clinical neuroscience conditions--understanding the effects of these models on brain function could be very helpful.
• It is safer and easier to study drug effects (i.e. anesthetic agents) in the mouse model than in humans

 With these issues in mind, it is exciting to see the recent research summary from Dr. Brian White and colleagues at Washington University in St. Louis in Plos One. Dr. White proposes the method and model for examining fMRI in mice. He summarizes results from fMRI performed in 5 mice using optical intensity signal imaging (OIS). He starts out with one of the simplest fMRI challenges--functional connectivity mapping. This technique uses an imaging model of the resting brain examining correlations between various regions. These correlations suggest connectivity between specific brain regions. A brain with a known specific function, i.e. vision can be assigned a region (or seed) of interest and correlations with that region can be evidence of brain connectivity with the region.

Here is a summary of some of the key findings from the study:

• Mice show left-right symmetrical connectivity (similar to humans) but less anterior-posterior connectivity
• Olfactory, cingulate and frontal regions show connectivity suggesting an intact limbic system network
• A default network appears in the mouse retrosplenial area--this is proposed as early evolutionary component of the human default network that would involve the human dorsolateral prefrontal cortex and the lateral parietal cortex

The authors note fMRI imaging is much less costly than in humans although the estimated cost is not listed in the manuscript. The minimum equipment cost for 3T fMRI in humans in about $3 million with high technical maintenance costs.

So look for expansion of the technology for functional brain imaging in the mouse model. Another example of how man and mouse can work together to better understand the brain and provide insight into the mechanism and potential treatments for clinical neuroscience disorders.

Image of fMRI correlations between regions using 8 different seed regions courtesy of Plos One open access.

White, B., Bauer, A., Snyder, A., Schlaggar, B., Lee, J., & Culver, J. (2011). Imaging of Functional Connectivity in the Mouse Brain PLoS ONE, 6 (1) DOI: 10.1371/journal.pone.0016322