Abstract
A comparison of the different types of resting state reveals some interesting characteristics of spontaneous brain activity that cannot be found in a single condition. Differences in the amplitude of low-frequency fluctuation (ALFF) between the eyes open (EO) and the eyes closed (EC) almost have a spatially distinct pattern with traditional EO-EC activation within sensory systems, suggesting the divergent functional roles of ALFF and activation. However, the underlying mechanism is far from clear. Since the thalamus plays an essential role in sensory processing, one critical step toward understanding the divergences is to depict the relationships between the thalamus and the ALFF modulation in sensory regions. In this preliminary study, we examined the association between the changes of ALFF and the changes of thalamic functional connectivity (FC) between EO and EC. We focused on two visual thalamic nuclei, the lateral geniculate nucleus (LGN) and the pulvinar (Pu). FC results showed that LGN had stronger synchronization with regions in lateral but not in medial visual networks, while Pu had a weaker synchronization with auditory and sensorimotor areas during EO compared with EC. Moreover, the patterns of FC modulation exhibited considerable overlaps with the ALFF modulation, and there were significant correlations between them across subjects. Our findings support the crucial role of the thalamus in amplitude modulation of low-frequency spontaneous activity in sensory systems, and may pave the way to elucidate the mechanisms governing distinction between evoked activation and modulation of low-frequency spontaneous brain activity.
Highlights
Accumulating evidence has suggested that spontaneous blood oxygenation level-dependent (BOLD) signal measured in the resting human brain is organized (Biswal et al, 1995; Lowe et al, 1998; Cordes et al, 2000; Greicius et al, 2003; Fox and Raichle, 2007)
We have consistently revealed that between eyes open (EO) and eyes closed (EC), the amplitude of low-frequency fluctuation (ALFF, Zang et al, 2007) exhibited symmetrically distributed and highly reproducible differences that were located in the extrastriate areas and non-visual sensory modalities, including primary auditory cortex (PAC) and somatosensory areas (Yan et al, 2009; Liu D. et al, 2013; Yuan et al, 2014; Zou et al, 2015; Zhang et al, 2018), with little overlap with the expected primary visual cortex (PVC)
The results showed that the optic radiation could be tracked in all subjects, thereby suggesting the accuracy of lateral geniculate nucleus (LGN) positions in all subjects
Summary
Accumulating evidence has suggested that spontaneous blood oxygenation level-dependent (BOLD) signal measured in the resting human brain is organized (Biswal et al, 1995; Lowe et al, 1998; Cordes et al, 2000; Greicius et al, 2003; Fox and Raichle, 2007). Most studies focused on a single condition to depict the resting brain networks (Fox and Raichle, 2007; Power et al, 2011; Yeo et al, 2011), to compare functional organization between normal subjects and patients (Greicius, 2008; Fox and Greicius, 2010; Zhang and Raichle, 2010) or to study intrinsic BOLD signal variability (Zang et al, 2007; Zou et al, 2008). Spontaneous brain activity can presumably be modulated by external or internal environments in a very different way from traditional task evoked activation, which might encode their divergent functional roles
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