Meeting Abstract
2.1 Monday, Jan. 4 Manganese-enhanced magnetic resonance imaging in the frog brain COATES, M. M.*; NARINS, P. M.; University of California, Los Angeles mcoates@ucla.edu
Anuran amphibians (frogs and toads) have long been recognized as excellent organisms for studying auditory processing and physiology. Frogs rely strongly on auditory communication: they call to attract mates and establish territories. To date, however, most available methods for studying auditory processing in frogs are highly invasive and do not allow for longitudinal studies. To address this problem, we have modified a manganese-enhanced MRI (MEMRI) technique developed for rodents as a noninvasive method for mapping physiological parameters in the frog brain. With this technique, manganese chloride (MnCl2) is administered systemically and manganese ions (Mn2+) are taken up through voltage-gated Ca2+ channels in synaptically activated neurons. Mn2+ then accumulates in active neurons and because it is paramagnetic, leads to enhanced contrast in T1-weighted MRI. This offers the ability to map accumulated stimulus-evoked activity. We use a Bruker 7 Tesla (7T) horizontal animal scanner to acquire high resolution (150 μm) brain maps. MEMRI has the potential for a range of functional neuroimaging studies where maps are produced in response to a variety of sensory stimuli (auditory, visual, motor, etc.) or to a combination of sensory stimuli to investigate multisensory processes. Preliminary results reveal that 24-hour noise stimulation produces a detectable signal in the torus semicircularis of the midbrain, and ongoing experiments will explore the locus of activity in response to auditory-plus-visual stimuli. [Supported by NIH grant no. DC00222 to PMN].
