![]() Perhaps most surprisingly, partial directed coherence and Granger causality-sometimes regarded as equivalent measures of directed influence-diverged profoundly. Notable exceptions to this were the correlation of coherence with PPC and PLV that was found in most cases, and partial correspondence between these three measures and Granger causality. Except for three pairwise correlations-PLV with PPC, PDC with DTF and parametric with non-parametric Granger causality-almost none of the analysed metrics consistently co-varied with any of the other measures across the three connections and two genotypes analysed. Using the detectability of coupling deficits in Gria1 −/− mice and bivariate correlations within animals as criteria, we found that across such measures, there is a considerable lack of functional redundancy. We applied these analyses to simultaneous field recordings from the prefrontal cortex and the ventral and dorsal hippocampus in the schizophrenia-related Gria1-knockout mouse model which displays a robust novelty-induced hyperconnectivity phenotype. In order to test this assumption, we here comparatively assessed a broad range of directional and non-directional metrics like coherence, Weighted Phase Lag Index (wPLI), phase-locking value (PLV), pairwise phase consistency (PPC), parametric and non-parametric Granger causality (GC), partial directed coherence (PDC), directed transfer function (DTF), spike-phase coupling (SPC), cross-regional phase-amplitude coupling, amplitude cross-correlations and others. However, in individual studies, typically, only very few measures of coupling are reported and, hence, redundancy across such indicators is implicitly assumed. In rodent models, various metrics have been used to quantify inter-regional neuronal communication. Communication between brain areas has been implicated in a wide range of cognitive and emotive functions and is impaired in numerous mental disorders.
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