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キーワード:
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要旨:
The cortical representation and processing of sensory afferent impulses is crucial for the fine coordination of complex brain and bodily responses to salient events. One specialized brain region, the insular cortex (IC), represents sensory inputs related to interoception and gustation. We examined the functional organization of distinct IC subregions using multi-modal stimuli with fMRI and electrophysiology in macaque monkeys and, to a lesser extent, fMRI in humans. The gustatory pathway was stimulated using various sets of taste stimuli, including sweet, sour and salty tastants applied to the tongue at high- and low-intensity concentrations. Despite individual variations in both species, consistent BOLD signal changes emerged in the anteroposterior mid-dorsal fundus and the most anterior aspect of the fundus, with a distinct separation of several millimeters from the middle representation. We also probed the interoceptive pathway using transcutaneous stimulation of the auricular branch of the vagus nerve (tVNS), rectal distention (RD), and local skin temperature changes in macaque monkeys. Thermal stimulation of the hand and foot consistently produced positive BOLD signal changes in a region posterior to the middle taste representation. Both RD and tVNS variably activated a smaller region near the taste representation and another region in the ventral anterior aspect of the IC, a region which has been related to a network of high-order cognitive functions and top-down influence on the autonomic nervous system. Electrophysiological recordings throughout the insula in macaque monkeys largely confirmed this topography. These non- or minimally-invasive stimulations of the primary interoceptive cortex provide the first multi-modal mapping of bodily functions in the IC. This work is an important first step towards understanding the neurobiology of subjective feelings and the relation of brain and bodily states during high-order emotional and cognitive functions.
