Dissociation of Connectivity for Syntactic Irregularity and Perceptual Ambiguity in Musical Chord Stimuli

Abstract

Musical syntax has been studied mainly in terms of “syntactic irregularity” in harmonic/melodic sequences. However, “perceptual ambiguity” referring to the uncertainty of judgment/classification of presented stimuli can in addition be involved in our musical stimuli using three different chord sequences. The present study addresses how “syntactic irregularity” and “perceptual ambiguity” on musical syntax are dissociated, in terms of effective connectivity between the bilateral inferior frontal gyrus (IFGs) and superior temporal gyrus (STGs) by linearized time-delayed mutual information (LTDMI). Three conditions were of five-chord sequences with endings of dominant to tonic, dominant to submediant, and dominant to supertonic. The dominant to supertonic is most irregular, compared with the regular dominant to tonic. The dominant to submediant of the less irregular condition is the most ambiguous condition. In the LTDMI results, connectivity from the right to the left IFG (IFG-LTDMI) was enhanced for the most irregular condition, whereas that from the right to the left STG (STG-LTDMI) was enhanced for the most ambiguous condition (p = 0.024 in IFG-LTDMI, p < 0.001 in STG-LTDMI, false discovery rate (FDR) corrected). Correct rate was negatively correlated with STG-LTDMI, further reflecting perceptual ambiguity (p = 0.026). We found for the first time that syntactic irregularity and perceptual ambiguity coexist in chord stimulus testing musical syntax and that the two processes are dissociated in interhemispheric connectivities in the IFG and STG, respectively.

Bidirectional connectivity changes in the frontotemporal areas reflect figure–ground reversal in multivoiced music

“…Accordingly, the directional information flow in frontotemporal connectivity could explain how the left IFG and the right HG collaborate in processing target phrases. The IFG and HG are pivotal areas for music perception, and their connectivity is discussed in relation to syntax processes [24][25][26] , categorization 27 , and the working memory of melody process 28 . Thus, frontotemporal connectivity between the IFG and HG is likely modulated by both a top-down process based on knowledge of the TTLS melody and a bottom-up process based on new information on voices accumulated while sequentially listening to target and cue phrases in each variation 29,30 .…”

“…The effective connectivity for the 12 connections between regional sources of the bilateral HGs and IFGs was estimated using MATLAB 7.7.0.471 (Math Works Inc., Natick, MA, USA) (see also Supplementary Table 1 for individual LTDMI values calculated for 12 connections). LTDMI was used to estimate information transmission between two time series based on mutual information (MI) 11,24 . For each subject, the mean LTDMI for the 2,100-ms epoch was calculated for each of 4 target phrases (T1, T2, T3, and T4) ×2 variations ( Variations II and IV) .…”

Harmonization of the fastest and densest responses embodies the humanlike reaction time of mice

“…Furthermore, their behavior during a trial, which includes repeated actions such as licking, nose poking, and lever pressing, complicates the interpretation of an RT-like measure. In animal studies, the stimulus-response relationship per trial may not be one-to-one, as in human studies [32][33][34] . Whether the delayed latencies of repeated responses accurately reflect the animals' decision-making points in the cognitive process is unclear.…”