  Functional Magnetic Resonance Imaging (fMRI) is predominantly harnessed for
spatially mapping activation foci along distributed pathways. However,
resolving dynamic information on activation sequence remains elusive. Here, we
show an ultra-fast fMRI (ufMRI) approach - a facilitating non-invasive
methodology for mapping Blood-Oxygenation-Level-Dependent (BOLD) response
timings in distributed pathways with high spatiotemporal sensitivity and
resolution. The mouse visual pathway was investigated under both normal and
dark reared conditions. Results show that BOLD responses of normal reared mice
preserve the neural input order from onset to peak times. However, modulatory
effects in cortical responses due to dark rearing are only measurable at early
response timings while a general delay in responses is measured at later
timings. Our findings highlight the importance of robustly measuring early BOLD
timings and pave the way for a better understanding and interpretation of
functional MRI in healthy and aberrant conditions.
