—A new method was introduced to enhance fMRI data analysis by reproducibility-based ICA. Using this new method, unreliable components were first identified and removed by computing reproducibility index from multiple ICA realizations. The... more
—A new method was introduced to enhance fMRI data analysis by reproducibility-based ICA. Using this new method, unreliable components were first identified and removed by computing reproducibility index from multiple ICA realizations. The remaining components were further denoised by elliminating known artifacts according to given criteria. The resultant data were enhanced in terms of statistical power. A simulation was presented to demonstrate the capability of the method to extract true components from noisy data, and an experimental dataset was used to examine the performance of the method in real contexts.
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—As one major line of research on brain plasticity, many imaging studies have been conducted to identify the functional and structural reorganization associated with musical expertise. Based on previous behavioral research, the present... more
—As one major line of research on brain plasticity, many imaging studies have been conducted to identify the functional and structural reorganization associated with musical expertise. Based on previous behavioral research, the present study used functional magnetic resonance imaging to identify the neural correlates of superior verbal memory performance in musicians. Participants with and without musical training performed a verbal memory task to first encode a list of words auditorily delivered and then silently recall as many words as possible. They performed in separate blocks a control task involving pure tone pitch judgment. Post-scan recognition test showed better memory performance in musicians than non-musicians. During memory retrieval, the musicians showed significantly greater activations in bilateral though left-lateralized visual cortex relative to the pitch judgment baseline. In comparison, no such visual cortical activations were found in the non-musicians. No group differences were observed during the encoding stage. The results echo a previous report of visual cortical activation during verbal memory retrieval in the absence of any visual sensory stimulation in the blind population, who are also known to possess superior verbal memory. It is suggested that the visual cortex can be recruited to serve as extra memory resources and contributes to the superior verbal memory in special situations. While in the blind population, such cross-modal functional reorganization may be induced by sensory deprivation; in the musicians it may be induced by the long-term and demanding nature of musical training to use as much available neural resources as possible.
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Recent studies have demonstrated resting-state abnormalities in midline regions in vegetative state=unresponsive wakefulness syndrome and minimally conscious state patients. However, the functional implications of these resting-state... more
Recent studies have demonstrated resting-state abnormalities in midline regions in vegetative state=unresponsive wakefulness syndrome and minimally conscious state patients. However, the functional implications of these resting-state abnormalities remain unclear. Recent findings in healthy subjects have revealed a close overlap between the neural substrate of self-referential processing and the resting-state activity in cortical midline regions. As such, we investigated task-related neural activity during active self-referential processing and various measures of resting-state activity in 11 patients with disorders of consciousness (DOC) and 12 healthy control subjects. Overall, the results revealed that DOC patients exhibited task-specific signal changes in anterior and posterior midline regions, including the perigenual anterior cingulate cortex (PACC) and posterior cingulate cortex (PCC). However , the degree of signal change was significantly lower in DOC patients compared with that in healthy subjects. Moreover, reduced signal differentiation in the PACC predicted the degree of consciousness in DOC patients. Importantly, the same midline regions (PACC and PCC) in DOC patients
Sensorysubstitutionhasbeenreportedinrecentbrainimagingstudieswithblindpeopleandotherswithsensorydeficitsso thatsensorycorticalregionstraditionallyconsideredunimodalrespondtostimulationfromothersensorymodalities.Similareffectsare... more
Sensorysubstitutionhasbeenreportedinrecentbrainimagingstudieswithblindpeopleandotherswithsensorydeficitsso thatsensorycorticalregionstraditionallyconsideredunimodalrespondtostimulationfromothersensorymodalities.Similareffectsare alsofoundfornormalsightedpeoplewithsensorydeprivation(blindfolded),indicativeofpre-existingneuronalpathwaysformultiple sensoryinteractions.Suchpathwaysareconsideredlatentinthattheyonlybecomeunmaskedorpotentiatedintheeventofsensory deafferentation,althoughwhethersensorydeprivationisnecessarytoexposethesepathwaysisunclearduetoinconclusiveevidence. Witharelativelystrongpowerinexperimentaldesign,visualcorticalactivationwasobservedwhennormalsightedparticipants(not blindfolded)judgedwhetherauditorily-presentednounsreferredtoartificialornaturalobjects.Theresultssuggesttheabovementioned pathwayscanbeexposedwithoutsensorydeafferentationandthereforearenottotallylatent.Thisestablishesaboundarycondition constrainingtheoreticalmodelsfortheneuralbasisofmultiplesensoryinteractions.
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Individual differences in mind and behavior are believed to reflect the functional variability of the human brain. Due to the lack of a large-scale longitudinal dataset, the full landscape of variability within and between individual... more
Individual differences in mind and behavior are believed to reflect the functional variability of the human brain. Due to the lack of a large-scale longitudinal dataset, the full landscape of variability within and between individual functional connectomes is largely unknown. We collected 300 resting-state functional magnetic resonance imaging (rfMRI) datasets from 30 healthy participants who were scanned every three days for one month. With these data, both intra-and inter-individual variability of six common rfMRI metrics, as well as their test-retest reliability, were estimated across multiple spatial scales. Global metrics were more dynamic than local regional metrics. Cognitive components involving working memory, inhibition , attention, language and related neural networks exhibited high intra-individual variability. In contrast, inter-individual variability demonstrated a more complex picture across the multiple scales of metrics. Limbic, default, frontoparietal and visual networks and their related cognitive components were more differentiable than somatomotor and attention networks across the participants. Analyzing both intra-and inter-individual variability revealed a set of high-resolution maps on test-retest reliability of the multi-scale connectomic metrics. These findings represent the first collection of individual differences in multi-scale and multi-metric characterization of the human functional connectomes in-vivo, serving as normal references for the field to guide the use of common functional metrics in rfMRI-based applications.
Research Interests: Algorithms, Principal Component Analysis, Magnetic Resonance Imaging, Independent Component Analysis, Brain Mapping, and 13 moreBrain, Humans, Female, Neuroimage, Male, Three Dimensional Imaging, Young Adult, Aged, Reproducibility, Reproducibility of Results, Sensitivity and Specificity, Resting State, and Connectome
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The default network of the human brain has drawn much attention due to its relevance to various brain disorders, cognition, and behavior. However, its functional components and boundaries have not been precisely defined. There is no... more
The default network of the human brain has drawn much attention due to its relevance to various brain disorders, cognition, and behavior. However, its functional components and boundaries have not been precisely defined. There is no consensus as to whether the precuneus, a hub in the functional connectome, acts as part of the default network. This discrepancy is more critical for brain development and aging studies: it is not clear whether age has a stronger impact on the default network or precuneus, or both. We used Generalized Ranking and Averaging Independent Component Analysis by Reproducibility (gRAICAR) to investigate the lifespan trajectories of intrinsic functional networks. By estimating individual-specific spatial components and aligning them across subjects, gRAICAR measures the spatial variation of component maps across a population without constraining the same components to appear in every subject. In a cross-lifespan fMRI dataset (N = 126, 7–85 years old), we observed stronger age dependence in the spatial pattern of a precuneus–dorsal posterior cingulate cortex network compared to the default network, despite the fact that the two networks exhibit considerable spatial overlap and temporal correlation. These results remained even when analyses were restricted to a subpopulation with very similar head motion across age. Our analyses further showed that the two networks tend to merge with increasing age. Post-hoc analyses of functional connectivity confirmed the distinguishable cross-lifespan trajectories between the two networks. Based on these observations, we proposed a dynamic model of cross-lifespan functional segregation and integration between the two networks, suggesting that the precuneus network may have a different functional role than the default network, which declines with age. These findings have implications for understanding the functional roles of the default network, gaining insight into its dynamics throughout life, and guiding interpretation of alterations in brain disorders. Published by Elsevier Inc.