Functional Magnetic Resonance Imaging: The Hemodynamic Inverse Problem

Abstract

Neuronal activity demands glucose and oxygen supplies, which are delivered by circulating blood. Averaged neuronal activity can predict temporally prolonged hemodynamic responses as described by linear transform models. Inferences in the opposite direction, though, from hemodynamic responses to neuronal activity, are made in the case of functional magnetic resonance imaging (fMRI). The validity of these inferences is under debate and constitutes the “hemodynamic inverse problem”. The present review briefly describes the properties of the fMRI technique and continues to present experimental evidence supporting the view that the underlying neuronal activity can be successfully captured in the fMRI signal in a roughly linear way and in a timescale down to a few hundred milliseconds.