ABSTRACT
Functional neuroimaging techniques based on hemodynamics (positron emission tomography, functional magnetic resonance imaging) and those based on electrophysiology (electroencephalography, magnetoencephalography and their stimulus-related counterparts) provide complementary information regarding both normal and pathological brain function. Many details of the relation between neuronal activation and consequent changes of blood flow, volume, and oxygenation remain unclear. Hemodynamic regulation is also known to vary between brain regions and to be different in the very young and the elderly. This is particularly problematic when brain imaging techniques are applied to patients with cerebral infarct or stroke. In the diseased brain, the relation between neuronal and hemodynamic measures is particularly complicated, because mechanisms regulating various aspects of hemodynamic function are likely to be differentially affected by disease processes. An ability to quantitatively assess the relation of hemodynamic and functional states of cerebral tissue would be useful to both basic cognitive neuroscience and in the management of cerebral disease (see M.D.Ginsberg & J.Bogousslavsky, 1998, for an overview of current practice and research in the diagnosis and manage-ment of stroke). Among the currently available functional imaging modalities only noninvasive optical imaging, a relative newcomer to the field, hasthe potential to simultaneously measure both hemodynamic and neuronalaspects of cerebral physiology. This dual capability makes noninvasive optical imaging an exciting tool for investigating the relation between hemodynamics and neuronal activity In this chapter I provide a briefintroduction to some of the issues underlying functional neuroimagingstudies of stroke as well as to recent work demonstrating the ability of optical imaging to simultaneously measure hemodynamic and neuronal phenomena in well-defined cortical regions.
