Neuroimaging in communication sciences and disorders: an introduction.

Localization of function within the brain has been a cornerstone for understanding an array of communication disorders. Scientific study of the link between focal brain regions and human behaviors now spans two centuries. However, our ability to observe the brain ‘‘in action’’ is a relatively recent event. Early studies of cognitive-related change in blood flow began to populate the literature in the mid-1970s (e.g., Franzen & Ingvar, 1975; Risberg, Halsey, Wills, & Wilson, 1975). Although this technique provided only a two-dimensional map of regional activation, and was gross by today’s standards, this work signaled quantitative leap in the ability to study the normal brain, as well as the impaired brain. With the advent of PET, three-dimensional mapping became possible, with anatomical location improved through co-registration of PET images to MRI images of the same subjects. A major limitation to PET as a research tool today is its limited availability. PET imaging not only requires a knowledgeable research team to conduct studies, but considerable infrastructure to maintain the PET scanner and its associated facilities. With the advent of fMRI, a technique became available that used equipment in common use for medical purposes. Furthermore, it did not require the manufacture and use of radioisotopes required by PET. These factors have contributed to the recent explosion in neuroimaging studies. To illustrate, Medline lists 10 human-oriented fMRI studies before 1995 and over 1300 in 2001. The papers in this volume present examples of neuroimaging applications in areas of research central to the field of communication sciences and disorders.