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Zusammenfassung:
The anterior insular cortex (AIC) is often regarded as a key “node” of the saliency network with a role in coordinating brain network activity after detection of homeostatic changes. In addition, distinct areas of the AIC project to homeostatic brainstem centers and could therefore act as a cortical output stage for the concurrent regulation of physiological and behavioral emotional responses to salient events. Given the possible role of the AIC in switching brain network dynamics and in descending autonomic regulations, we combined electrical microstimulation and functional magnetic resonance imaging (fMRI) using a 7T scanner to examine the effect of electrical microstimulation of the AIC on the blood-oxygen-level-dependent (BOLD) signal in both the subcortical homeostatic centers and the neocortex in 5 anesthetized macaque monkeys. Single channel glass isolated iridium electrodes were used to deliver 200-μs biphasic charge-balanced pulses with stimulation frequencies of 5, 40, 60 and 100 Hz during two-shot echo-planar imaging (EPI) with a temporal resolution of 2 seconds (Logothetis et al. Nature Nsci 2010 13:1283-91). Electrical microstimulation of the left or the right AIC produced strong positive and negative BOLD signal changes in both cortical and subcortical regions. In some sessions, there was a distinct but varying activation of all subcortical centers known to receive monosynaptic projections from the AIC (hypothalamus, periaqueductal gray, parabrachial nucleus). However, in most sessions, this pattern was accompanied or replaced with massive activation or deactivation of the neocortex, in particular primary sensory areas, with a trend for the left and right AIC to produce more prevalently cortical activations and deactivations, respectively. These effects, coupled with our tract-tracing and NET-fMRI data, begin to unravel the functional organization underlying the role of the AIC in brain network dynamics and brainstem autonomic control regulation.