＜Symposium I＞Transient neural energetics by fMRI for brief and long stimuli

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Neuronal activity mapping of cerebral functions using oxidative energetics has become an acceptedfunctional magnetic resonance imaging （fMRI） technique, termed calibrated fMRI. It requires calculation of oxygenconsumption （CMRO2） from blood oxygenation level dependent （BOLD） signal using multi-modal measurementsof blood flow （CBF） and volume （CBV）. This approach is based on a biophysical model which describes tissueoxygen extraction at steady-state, therefore it is unclear if this conventional steady-state BOLD model can be appliedtransiently for calculating dynamic CMRO2 changes. In particular, it is unknown whether calculation of CMRO2 fromcalibrated fMRI differs between brief and long stimuli. In this study linearity was experimentally demonstratedbetween BOLD-related components and neural activity. We used multi-modal fMRI （at 11.7T） and neuronal signalmeasurements of local fi eld potential （LFP） and multi-unit activity （MUA） in α-chloralose anesthetized rats duringforepaw stimulation to show that respective transfer functions （of BOLD, CBV, CBF） generated by deconvolutionwith LFP（ or MUA） are time invariant, for events in the millisecond to minute range. Since the transfer functions aretime invariant for event-related and steady-state stimuli, it is possible to use calibrated fMRI in a dynamic manner.The multi-modal results allowed assignment of a significant component of the BOLD signal that can be ascribedto CMRO2 transients. Here we discuss the importance of minimizing residual signal, represented by the diff erencebetween modeled and raw signals, in convolution analysis using multi-modal fMRI and neural signals.

＜Symposium I＞Transient neural energetics by fMRI for brief and long stimuli

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