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Abstract:
The primate brain is a complex dynamical system displaying long-range temporally-correlated functional networks. In the absence of external stimulation, several so called resting state functional networks of spontaneous activity have been identified. Their origin and function are not well understood, but such intrinsic architecture could reflect neural fluctuations within anatomically connected areas or active mechanisms related to perception and awareness. On the other hand, when the brain is being stimulated, a different pattern of stimulus-evoked activity emerges. How the brain orchestrates those interwoven patterns of activity is still unclear. We sought to assess the relationship between resting-state and stimulus-driven functional networks by investigating their topographical correspondence by using functional magnetic resonance imaging (fMRI) under specific stimulus paradigms. To this end, we scanned two monkeys (Macaca mulatta), while anesthetized or awake, stimulated with three main paradigms: a) no visual stimulation, b) visual stimulation using a one-minute block-design displaying natural movie clips alternated with gray background, and c) continuous visual stimulation using uninterrupted natural movies. Using independent component analysis (ICA), we were able to recover topographically similar patterns of resting state networks contained in stimulus-driven datasets. This suggests that, under certain circumstances, the primate brain is able to cope with both types of functional networks independently. Moreover, our results provide implications for bidirectional causal influences between stimulus-driven and spontaneous activity. This work provides insights of how the brain organizes its functional architecture and we expect it can stimulate further analysis and reinterpretation of a wide range of existing neuroimaging and physiological data.
