Investigating the cortical mechanisms of conspecific voice perception in anesthetized marmosets using 3T fMRI

<ns4:p>Background Functional MRI studies have shown the existence of cortical areas selective for conspecific vocalizations (‘voice patches’) in the temporal lobe of both humans and macaques. Two recent studies using high-field small-animal fMRI also both evidenced anterior temporal voice patches in marmoset monkeys, suggestive of an evolutionary-old ‘primate voice patch system’. Here we asked whether similar findings could be observed at lower (3T) field strength in a conventional whole-body scanner. Methods Fifteen (n=15) adult marmosets were scanned using a 16-channel marmoset head coil and a dedicated ‘clustered-sparse’ sampling design during auditory stimulation with conspecific vocalizations and scrambled control stimuli while under sevoflurane-induced anesthesia. Results At the group level, we observed bilateral and symmetrical activation of auditory cortical and subcortical areas when contrasting the auditory stimulation conditions to the silent baseline. At the individual level auditory activation was more variable but sufficiently reliable to provide a valuable coincidence map of areas activated in common by seven different individuals. When contrasting the vocalizations to the scrambled controls, we found in these seven monkeys a bilateral activation of the anterior and temporal cortex. Conclusions Despite methodological optimizations, our study encountered several limitations, including a low signal-to-noise ratio (SNR) and reduced spatial resolution inherent to 3T fMRI, and the use of anesthesia, which decrease functional connectivity and activation reliability. However, we identified the same brain regions as those documented in the literature. Our results suggest that fMRI at 3T in clinical studies can provide clues to identify the networks involved in voice perception in marmosets – although they will be explored in much finer detail using small animal, ultra-high-filed and awake fMRI.</ns4:p>