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Publisher Summary This chapter focuses on functional maps generated by the hemodynamic brain mapping methods, that is, positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). It gives a brief introduction on how functional maps can be generated from functional neuroimaging data and indicates some conceptual limitations of these procedures. There are two basic types of brain mapping methods for measuring brain function, the techniques that detect the electromagnetic activity of the brain, measuring the electromagnetic fields generated by neural activity, and the techniques that are based on hemodynamic-metabolic signals, measuring the hemodynamic or metabolic traces of neural activity. The electromagnetic methods produce data with limited spatial resolution in terms of source localization but a temporal resolution in the millisecond range. High temporal resolution is important to resolve the rapidly changing patterns of brain activity that underlie cerebral function. The functional neuroimaging techniques, in particular PET measurements of regional cerebral blood flow (rCBF) and fMRI based on the blood oxygenation level dependent contrast are unique in providing data from much of the brain simultaneously. This allows not only the investigation of a single brain area but also which brain regions work together during the performance of specific tasks. Thus, PET and fMRI data can provide evidence for whether a particular cognitive operation is localized to a specific focus or is distributed across several brain areas. |
