Abstracts

The hemodynamic changes associated with neuronal activity are the basis for several non-invasive imaging methods, such as fMRI, PET and SPECT. However, the precise spatiotemporal relationship between perfusion, oxygenation and the neuronal dynamic is not well understood since there is no technique for simultaneously measuring neuronal activity and perfusion in a large area of cortex with high spatial and temporal resolution., Currently, optical recording of voltage sensitive dyes (VSD) offers the best spatial ([sim]50[mu]m) and temporal (1ms) resolution for recording neuronal activity from a large area of cortex (several millimeters). Intrinsic optical signal (IOS) imaging offers the best spatial ([sim]50[mu]m) and temporal (tens of milliseconds) resolution for recording hemodynamic changes. We developed a technique combining VSD and IOS imaging to simultaneously measure membrane potential, perfusion and hemoglobin oxygenation [italic]in vivo[/italic]., Two illumination sources were employed for VSD (640[plusmn]10nm, for new blue dye RH-1692) and IOS (570[plusmn]5 or 605[plusmn]5) respectively. A 620nm dichroic mirror was used to separate the VSD ([gt]665nm) and IOS signals (570 or 605 nm). VSD and IOS responses were simultaneously recorded with two cameras. We compared the IOS result from cortex stained with VSD and IOS result from unstained cortex and found that staining with RH-1692 has no significant effect on the hemodynamic responses. We successfully used this technique in the rat preparation to record interictal events induced with intracortical injection of bicuculline., Simultaneous VSD and IOS recording is a technically feasible method for studying the complex interactions between excitatory and inhibitory neuronal activity and both increases and decreases in perfusion and oxygenation., (Supported by NIH NS043799-04, NS049482-01 and the Epilepsy Foundation through the generous support of the American Epilepsy Society.)