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Title: Causal interactions between frontalθ - parieto-occipitalα2 predict performance on a mental arithmetic task
Authors: Dimitriadis, S.I
Sun, Y 
Thakor, N.V 
Bezerianos, A 
Keywords: adult
cognitive workload level
controlled study
correlation analysis
frontal lobe
functional connectivity
human experiment
information processing
mental arithmetic
mental performance
normal human
occipital lobe
parietal lobe
rank sum test
scanning electron microscopy
transcranial magnetic stimulation
working memory
Issue Date: 2016
Citation: Dimitriadis, S.I, Sun, Y, Thakor, N.V, Bezerianos, A (2016). Causal interactions between frontalθ - parieto-occipitalα2 predict performance on a mental arithmetic task. Frontiers in Human Neuroscience 10 (42614) : 454. ScholarBank@NUS Repository.
Rights: Attribution 4.0 International
Abstract: Many neuroimaging studies have demonstrated the different functional contributions of spatially distinct brain areas to working memory (WM) subsystems in cognitive tasks that demand both local information processing and interregional coordination. In WM cognitive task paradigms employing electroencephalography (EEG), brain rhythms such as θ and α have been linked to specific functional roles over given brain areas, but their functional coupling has not been extensively studied. Here we analyzed an arithmetic task with five cognitive workload levels (CWLs) and demonstrated functional/effective coupling between the two WM subsystems: the central executive located over frontal (F) brain areas that oscillates on the dominant θ rhythm (Frontalθ/Fθ) and the storage buffer located over parieto-occipital (PO) brain areas that operates on the α2 dominant brain rhythm (Parieto-Occipitalα2/POα2). We focused on important differences between and within WM subsystems in relation to behavioral performance. A repertoire of brain connectivity estimators was employed to elucidate the distinct roles of amplitude, phase within and between frequencies, and the hierarchical role of functionally specialized brain areas related to the task. Specifically, for each CWL, we conducted a) a conventional signal power analysis within both frequency bands at Fθ and POα2, b) the intra- and inter-frequency phase interactions between Fθ and POα2, and c) their causal phase and amplitude relationship. We found no significant statistical difference of signal power or phase interactions between correct and wrong answers. Interestingly, the study of causal interactions between Fθ and POα2 revealed frontal brain region(s) as the leader, while the strength differentiated between correct and wrong responses in every CWL with absolute accuracy. Additionally, zero time-lag between bilateral Fθ and right POa2 could serve as an indicator of mental calculation failure. Overall, our study highlights the significant role of coordinated activity between Fθ and POα2 via their causal interactions and the timing for arithmetic performance. © 2016 Dimitriadis, Sun, Thakor and Bezerianos.
Source Title: Frontiers in Human Neuroscience
ISSN: 16625161
DOI: 10.3389/fnhum.2016.00454
Rights: Attribution 4.0 International
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