Development of a non-invasive novel individual marmoset holder for evaluation by awake functional magnetic resonance brain imaging

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>Although functional MRI (fMRI) in awake marmosets (<jats:italic>Callithrix jacchus</jats:italic>) is fascinating for functional brain mapping and evaluation of brain disease models, it is difficult to launch awake fMRI on scanners with less than 15 cm of bore size. A universal marmoset holder for the small-bore size MRI was designed, and evaluated whether this holder could conduct auditory stimulation fMRI in the awake state.</jats:p></jats:sec><jats:sec><jats:title>New Method</jats:title><jats:p>The marmoset holder was designed with an outer diameter of 71.9 mm. A holder was designed to allow adjustment according to the individual head shape, enabling to use the holder universally. An awake fMRI study of auditory response was conducted to evaluate the practicality of the new holder. Whole-brain activation was investigated when marmosets heard the marmoset social communication “phee call,” an artificial tone sound, music (bossa nova), and reversed of those.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>The prefrontal cortex was significantly activated in response to phee calls, whereas only the auditory cortex was activated in response to pure tones. In response to bossa nova, the marmoset’s visual and auditory cortices were activated. In contrast, the auditory response was decreased when marmosets heard phee calls and bossa nova music played backward. Their stimulus-specific responses indicated they perceived and differentiated sound characteristics in the fMRI environment.</jats:p></jats:sec><jats:sec><jats:title>Comparison with Existing Methods</jats:title><jats:p>A holder does not require surgical intervention or custom-made helmet to minimize head movement in small space.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>Our newly developed holder made it possible to perform longitudinal fMRI experiments on multiple marmosets in a less invasive manner.</jats:p></jats:sec><jats:sec><jats:title>Highlight</jats:title><jats:list list-type="bullet"><jats:list-item><jats:p>We designed a universal marmoset holder for the optimization of small-bore size MRI. We aimed to evaluate whether the data acquired by fMRI with this holder indicated that awake marmosets were likely to recognize sounds during fMRI and whether the brain activity shown as fMRI signals reflected the characteristics of each sound.</jats:p></jats:list-item><jats:list-item><jats:p>After the acclimatization of the marmosets to the holder, an awake fMRI study was conducted to evaluate the practicality of the new holder and successfully acquired the auditory responses to the set of sound stimuli.</jats:p></jats:list-item><jats:list-item><jats:p>Our newly developed holder does not require surgical intervention to minimize head movement, which allows for less invasive fMRI experiments and makes it easier to conduct longitudinal fMRI for multiple marmosets.</jats:p></jats:list-item></jats:list></jats:sec>