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Somers, D. C.

Publications and source records attributed to Somers, D. C..

3 recordsLinked to original sources

Predicting an Individual's Cerebellar Activity from Functional Connectivity Fingerprints

The cerebellum is gaining scientific attention as a key neural substrate of cognitive function; however, individual differences in the cerebellar organization have not yet been well studied. Individual differences in functional brain organization can be closely tied to individual differences in brain connectivity. Connectome Fingerprinting is a modeling approach that predicts an individuals brain activity from their connectome. Here, we extend Connectome Fingerprinting (CF) to the cerebellum. We examined functional MRI data from 160 subjects (98 females) of the Human Connectome Project young adult dataset. For each of seven cognitive task paradigms, we constructed CF models from task activation maps and resting-state cortico-cerebellar functional connectomes, using a set of training subjects. For each model, we then predicted task activation in novel individual subjects, using their resting-state functional connectomes. In each cognitive paradigm, the CF models predicted individual subject cerebellar activity patterns with significantly greater precision than did predictions from the group average task activation. Examination of the CF models revealed that the cortico-cerebellar connections that carried the most information were those made with the non-motor portions of the cerebral cortex. These results demonstrate that the fine-scale functional connectivity between the cerebral cortex and cerebellum carries important information about individual differences in cerebellar functional organization. Additionally, CF modeling may be useful in the examination of patients with cerebellar dysfunction, since model predictions require only resting-state fMRI data which is more easily obtained than task fMRI.

neuroscience↗

Default Mode and Dorsal Attention Network functional connectivity associated with alpha and beta peak frequency in individuals.

Alpha- and Beta-frequency oscillatory waves are evident in resting-state electro- and magneto-encephalography (EEG, MEG). Higher peak frequencies for Alpha and Beta are associated with greater cognitive health. Aging slows down the alpha and beta waves which are also affected by mental states, disorders such as ADHD, and sleep deprivation. Functional magnetic resonance imaging (fMRI) of resting-state brain activity reveals anti-correlation of very low frequency (< 0.1 Hz) fluctuations between two distributed cerebral cortical networks, the Dorsal Attention Network (DAN) and the Default Mode Network (DMN). DAN activation is related to attentional demands in extrinsic tasks, whereas DMN is associated with mind wandering, episodic memory retrieval, and intrinsic processing. Prior research has found that higher DAN-DMN anticorrelation is related to greater cognitive and mental health. Here, we investigated whether these two measures of cognitive and mental health are related to each other within individuals. We investigated resting-state Functional Connectivity (rsFC) between the DMN and DAN using fMRI and alpha and beta peaks from MEG using two large datasets (n=89 and n=189). We found that more robust anti-correlations between DMN and DAN regions are related to higher peak frequencies of alpha and beta rhythms in the brain. Subjects with higher alpha peak frequencies also show stronger positive within-network connectivity in both the DMN and DAN networks. Females show stronger correspondence between the two measures as compared to males. This association between two non-invasive cognitive neuroscience modalities adds to the growing literature on the biomarkers of cognitive and mental health. Key pointsO_LIMEG/EEG biomarker of brain health is correlated with rs-fMRI biomarker of brain health C_LIO_LIAlpha and beta peak frequency correlated with DMN-DAN functional connectivity C_LIO_LIStronger within-network connectivity for subjects with a high alpha peak frequency C_LIO_LIFemales have a stronger association between peak frequency and DMN-DAN connectivity C_LI

neuroscience↗

Extended frontal networks for visual and auditory working memory

Working memory (WM) supports the persistent representation of transient sensory information. Visual and auditory stimuli place different demands on WM and recruit different brain networks. Separate auditory- and visual-biased WM networks extend into the frontal lobes, but several challenges confront attempts to parcellate human frontal cortex, including fine-grained organization and between-subject variability. Here, we use differential intrinsic functional connectivity from two visual-biased and two auditory-biased frontal structures to identify additional candidate sensory-biased regions in frontal cortex. We then examine direct contrasts of task fMRI during visual vs. auditory 2-back WM to validate those candidate regions. Three visual-biased and five auditory-biased regions are robustly activated bilaterally in the frontal lobes of individual subjects (N=14, 7 women). These regions exhibit a sensory preference during passive exposure to task stimuli, and that preference is stronger during WM. Hierarchical clustering analysis of intrinsic connectivity among novel and previously identified bilateral sensory-biased regions confirms that they functionally segregate into visual and auditory networks, even though the networks are anatomically interdigitated. We also observe that the fronto-temporal auditory WM network is highly selective and exhibits strong functional connectivity to structures serving non-WM functions, while the fronto-parietal visual WM network hierarchically merges into the multiple-demand cognitive system.

neuroscience↗