PMID- 26780815 OWN - NLM STAT- MEDLINE DCOM- 20170712 LR - 20171122 IS - 1558-0210 (Electronic) IS - 1534-4320 (Linking) VI - 24 IP - 10 DP - 2016 Oct TI - Revealing Cross-Frequency Causal Interactions During a Mental Arithmetic Task Through Symbolic Transfer Entropy: A Novel Vector-Quantization Approach. PG - 1017-1028 AB - Working memory (WM) is a distributed cognitive process that employs communication between prefrontal cortex and posterior brain regions in the form of cross-frequency coupling between theta ( theta) and high-alpha ( alpha2) brain waves. A novel method for deriving causal interactions between brain waves of different frequencies is essential for a better understanding of the neural dynamics of such complex cognitive process. Here, we proposed a novel method to estimate transfer entropy ( TE) through a symbolization scheme, which is based on neural-gas algorithm (NG) and encodes a bivariate time series in the form of two symbolic sequences. Given the symbolic sequences, the delay symbolic transfer entropy ( dSTE(NG)) is defined. Our approach is akin to standard symbolic transfer entropy ( STE) that incorporates the ordinal pattern (OP) symbolization technique. We assessed the proposed method in a WM-invoked paradigm that included a mental arithmetic task at various levels of difficulty. Effective interactions between Frontal(theta) ( F(theta) ) and [Formula: see text] ( PO(alpha2)) brain waves were detected in multichannel EEG recordings from 16 subjects. Compared with conventional methods, our technique was less sensitive to noise and demonstrated improved computational efficiency in quantifying the dominating direction of effective connectivity between brain waves of different spectral content. Moreover, we discovered an efferent F(theta) connectivity pattern and an afferent PO(alpha2) one, in all the levels of the task. Further statistical analysis revealed an increasing dSTE(NG) strength following the task's difficulty. FAU - Dimitriadis, Stavros AU - Dimitriadis S FAU - Sun, Yu AU - Sun Y FAU - Laskaris, Nikolaos AU - Laskaris N FAU - Thakor, Nitish AU - Thakor N FAU - Bezerianos, Anastasios AU - Bezerianos A LA - eng PT - Journal Article PT - Research Support, Non-U.S. Gov't DEP - 20160118 PL - United States TA - IEEE Trans Neural Syst Rehabil Eng JT - IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society JID - 101097023 SB - IM MH - Adult MH - Brain Waves/*physiology MH - Causality MH - Cerebral Cortex/*physiology MH - Cognition/*physiology MH - Computer Simulation MH - Concept Formation/physiology MH - Connectome/methods MH - Electroencephalography/methods MH - Entropy MH - Female MH - Humans MH - Male MH - *Mathematical Concepts MH - Memory, Short-Term/*physiology MH - *Models, Neurological MH - Models, Statistical MH - Task Performance and Analysis MH - Young Adult EDAT- 2016/01/19 06:00 MHDA- 2017/07/14 06:00 CRDT- 2016/01/19 06:00 PHST- 2016/01/19 06:00 [pubmed] PHST- 2017/07/14 06:00 [medline] PHST- 2016/01/19 06:00 [entrez] AID - 10.1109/TNSRE.2016.2516107 [doi] PST - ppublish SO - IEEE Trans Neural Syst Rehabil Eng. 2016 Oct;24(10):1017-1028. doi: 10.1109/TNSRE.2016.2516107. Epub 2016 Jan 18.