Mean amplitude of low frequency fluctuations measured by fMRI at 11.7T in the aging brain of mouse lemur primate

Non-human primates are a critical species for the identification of key biological mechanisms in normal and pathological aging. One of these primates, the mouse lemur, has been widely studied as a model of cerebral aging or Alzheimers disease. The amplitude of low-frequency fluctuations of blood oxygenation level-dependent (BOLD) can be measured with functional MRI. Within specific frequency bands (e.g. the 0.01-0.1 Hz), these amplitudes were proposed to indirectly reflect neuronal activity as well as glucose metabolism. Here, we first created whole brain maps of the mean amplitude of low frequency fluctuations (mALFF) in middle-aged mouse lemurs. Then, we extracted mALFF in old lemurs to identify age-related changes. A high level of mALFF was detected in the temporal cortex (Brodmann area 20), somatosensory areas (Brodmann area 5), insula (Brodmann area 13-6) and the parietal cortex (Brodmann area 7) of healthy middle-aged mouse lemurs. Aging was associated with alteration of mALFF in somatosensory areas (area 5) and the parietal cortex (area 7). Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=159 HEIGHT=200 SRC="FIGDIR/small/521367v2_ufig1.gif" ALT="Figure 1"> View larger version (59K): org.highwire.dtl.DTLVardef@15c9556org.highwire.dtl.DTLVardef@1505c78org.highwire.dtl.DTLVardef@e6f3fcorg.highwire.dtl.DTLVardef@9c6053_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIWe characterized mean amplitude of fluctuation at low frequencies (mALFF) in mouse lemurs. C_LIO_LImALFF was the highest in regions involved in visuo-somatosensory-motor function (Brodmann areas 5, 7, 20) and in more integrative functions (area 13-16). C_LIO_LImALFF was affected by aging in regions involved in visuo-somatosensory-motor function (parietal areas 5 and 7). C_LIO_LImALFF is a useful marker to investigate age-related cerebral dysfunction in animals. C_LI Significance StatementO_LIThe amplitude of low-frequency fluctuations (ALFF) is expected to reflect neuronal activity. It has been proposed as an MRI-based method to evaluate brain function. C_LIO_LIALFF has been used to investigate different cerebral pathologies in animal models but the regional differences of ALFF signal and the impact of cerebral aging on ALFF has never been characterized. C_LIO_LIHere, we highlight for the first time regional difference of ALFF. High signal was detected in regions involved in visuo-somatosensory-motor function as well as in more integrative functions. ALFF was reduced in regions involved in visuo-somatosensory-motor function during aging. ALFF is thus a useful marker to investigate age-related cerebral dysfunction. C_LI