Frequency-selective Functional Connectivity Based On The Tonotopic Differentiation Of The Human Auditory Cortex

The frequency selectivity of the resting-state functional connectivity(RS-FC)reflects the similarity of the frequency tuning between the neurons.RS-FC was significantly higher for the neurons or neuron populations with similar tuning properties than for neurons or neuron populations with dissimilar tuning properties.That is to say,the more similar the frequency tuning property of neurons is,the higher the degree of functional interaction between neurons.Recent research has demonstrated that RS-FC within the human auditory cortex(HAC)is frequency-selective,but whether RS-FC between the HAC and other brain areas is differentiated by frequency remains unclear.This thesis is based on the tonotopic differentiation of the HAC to investigate whether the functional communication between the HAC and other brain areas is frequency-selective.In this study,we made three sub-studies:(1)The tonotopic organization of the HAC;(2)The large scale resting-state functional brain network with the core of the HAC;(3)Whether the RS-FC between the HAC and other brain areas is frequency-selective were studied.(1)In experiment 1,we gathered task-based fMRI data under six frequencies of tone stimuli(200,400,800,1600,3200 and 6400 Hz);The task-activation study demonstrated that the tonotopic organization of the HAC is a high-to-low-to-high pattern across Heschl`s gyrus(HG).(2)In experiment 2,we gathered rs-fMRI data;then,the region of interest(ROI)of the HAC was defined according to the responses of 50 participants to the tone stimuli in experiment 1;and the ROI was used as seed to find RS-FC between the HAC and other brain regions.The results showed that there was RS-FC between the HAC and other brain regions which included superior temporal gyrus,prefrontal cortex(PFC),parietal cortex,occipital lobe,and subcortical structures.In experiment 2,a large scale resting-state functional brain network with the core of the HAC was established.(3)In experiment 3,six ROIs were defined according to the responses of 50 participants to six frequencies of tone stimuli in experiment 1.Then,these ROIs were used as seed to find RS-FC between each tonotopic sub-region of the HAC and other brain regions.At last,the statistical methods(repeated-measures one-way ANOVA)was used to determine whether there was significant difference among RS-FCs of different frequency categories.Significant differences among FCs were observed in most of the brain regions which have RS-FC with the HAC.In detail,there was stronger RS-FC between 1)low-frequencies(200 and 400 Hz)regions in the HAC and other brain regions including pre-motor cortex,somatosensory cortex,somatosensory-association cortex,and dorsolateral PFC;2)intermediate-frequencies(800 and 1600 Hz)regions in the HAC and other brain regions including anterior/posterior-superior temporal sulcus,supramarginal gyrus,and inferior frontal cortex;3)intermediate/low-frequencies regions and visual-related regions;4)high-frequencies(3200 and 6400 Hz)regions in the HAC and anterior-cingulate cortex or left-dorsolateral PFC.These findings demonstrate that the RS-FC between the HAC and other brain regions is frequency-selective.This thesis focuses on whether RS-FC between the HAC and other brain regions differentiated by frequency.We have investigated the tonotopic organization of the HAC,the large scale resting-state functional brain network with the core of the HAC,and whether the RS-FC between the HAC and other brain region is differentiated by frequency.The findings of this thesis not only refresh people's view about that the frequency selectivity of RS-FC only exists in the primary stage of sound information processing,but also have a guiding significance for further exploring the advanced cognitive functions of each tonotopic sub-regions of the HAC and further consummating the human brain auditory information processing model.