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Abstract:
The anterior insular cortex (AIC) is often regarded as a key “node” of the salience network that mediates the central representation and goal-directed control of homeostatic bodily states by coordinating brain networks. Given the possible role of the AIC in brain network dynamics, we combined electrophysiology and electrical microstimulation in the left and right AIC with functional magnetic resonance imaging (fMRI) to examine blood-oxygen-level-dependent (BOLD) signal changes in cortical and subcortical areas in 4 anesthetized macaque monkeys in a 7T scanner. 10-channel laminar electrodes were introduced in the ‘von Economo neuron area’ of the AIC to record ongoing spontaneous neuronal activity during two-shot echo-planar imaging with a temporal resolution of 2 seconds. Focusing on the local field potential gamma band (56-79 Hz) unilateral events were detected and used to trigger the BOLD signal, a method called ‘neural-event-triggered fMRI’ (NET-fMRI) (Logothetis et al. Nature 2012 491:547-53). The results showed markedly different patterns of whole-brain activation and deactivation for the left and right AIC. Subsequently, the laminar electrodes were replaced with single channel iridium electrodes to alternately deliver electrical microstimulation pulses (200μs biphasic charge-balanced pulses with a 100 Hz frequency) to the left and right AIC. Although the stimulations activated the same brain areas (e.g. amygdala, thalamus) the whole-brain activity following left stimulation tended to be stronger and more prevalent. These results, combined with our tract-tracing data begin to unravel the functional organization underlying the role of the AIC in functional brain networks and brainstem autonomic control regulation.
