A Pilot Study On Mechanisms Behind The Amplitude Modulation Of Low-frequency Fluctuations Between Resting State Types

The amplitude of low-frequency fluctuation(ALFF)is widely used in resting state functional Magnetic Resonance Imaging(resting state fMRI),but the physiological basis remains unclear.A comparison of different resting state conditions reveals some surprising results and may throw light on the mechanism.Differences of amplitude of low-frequency fluctuation(ALFF)between eyes open(EO)and eyes closed(EC)were mainly located in the lateral visual network,the auditory network and the sensorimotor areas,with little overlap with traditional activation regions(the medial visual network),suggesting that ALFF may have distinct functional role with activation.Considering the crucial role of the thalamus in sensory processing and the most significant external difference between EO and EC,here we studied the link between thalamus and differences in ALFF to get a better understanding of the comparison.Considering that the function of the thalamus is heterogeneous across different nuclei,the first study focused on three selected classical thalamus segmentation methods: spatial field(cortical functional connectivity(FC)based segmentation,seed-based connectivity analysis(SCA)combined with independent component analysis(ICA)based segmentation)and temporal field(instantaneous connectivity parcellation(ICP)),two groups of data were applied to repeat,compare and verify the methods.The verification(comparison with Morel's thalamus atlas)showed low Dice's coefficients(<0.4).The second study chose Morel's nuclei to test the initial hypothesis.Considering the most significant external difference between EO and EC(visual input or not),here we focused on two vision related nuclei,lateral geniculate nucleus(LGN)and pulvinar(Pu),calculated their respective FC and made a comparison with ALFF differences.It was found that LGN had a stronger FC in lateral but not in medial visual areas(EO > EC),and Pu had a weaker FC in auditory and sensorimotor regions under EO than EC.There's stable overlap and significant correlation between the two metrics(i.e.,FC and ALFF).To sum up,there's significant association between thalamus and ALFF differences.Our findings supported the crucial role of the thalamus in ALFF modulation and provide basis for the study of causal relationship.