Functional imaging of the auditory system: the use of positron emission tomography

Modern brain imaging methods now afford unprecedented opportunities for the in vivo study of central auditory system function. Positron emission tomography (PET) has been used as a functional imaging technique for more than 15 years to study the distribution of cerebral haemodynamic changes associated with auditory stimulation, in subjects with normal and abnormal auditory function. Many of these studies concern processes related to, but not identical with, audition, such as speech perception, melodic processing and directed attention. Additionally, PET has been used to explore auditory perception in clinical populations such as cochlear implantees, neurosurgical candidates and people with tinnitus and auditory hallucinations. The spatial resolution of PET does not appear sufficient to address questions of a fine anatomical grain, e.g. exploring functional specialization within the primary and secondary auditory cortex. Nevertheless, PET has considerable potential as a tool in basic research on, and clinical assessment of, many auditory phenomena. Although functional magnetic resonance imaging can now be used for many studies for which formerly only PET was suitable, PET still possesses unique advantages. For example, it permits acquisition of data from inferior frontal and anterior temporal areas, can be used with subjects with cochlear and other implants (such as pacemakers) and can be used to map neurochemical pathways and receptors.