ABSTRACT
Studies in monkeys indicate that somatosensory processing of innocuous tactile stimuli occurs within an interconnected cortical network, which mostly resides in the parietal cortex. The major regions include multiple subdivisions of the primary somatosensory area (SI) in the postcentral gyrus, the secondary somatosensory area (SII) in the parietal operculum, additional lateral cortical areas buried within the Sylvian fissure, portions of the supramarginal gyrus, and granular prefrontal cortex. This review focuses on homologous somatosensory representations in the cortex of humans that are revealed with non-invasive recording and neuroimaging methods. Critical to the validation of these observations is confirming characteristic features known from direct neural recordings, especially in monkeys. Brain imaging studies like positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) are especially appropriate in exposing the many cortical foci that respond during a single somatosensory stimulation paradigm. Non-invasive techniques have the great advantage of allowing replicate studies in conscious normal or patient populations performing a variety of tasks affecting tactile discrimination, sensorimotor integration, attention, and object recognition.
