Fig 1.
(A) The four triplets generated from the 6 sounds. The letters A to E are used to refer to the sounds. The first two items of the triplet are referred to as “root” and the last item as “ending”. Statistical deviants were created by varying the transition probability from root to ending within two levels, high (p = 0.9) and low (p = 0.1). Triplet roots (AB or CD) are occurring with a constant transitional probability (p = 0.5) after any of the triplet endings (E or F). (B) The auditory stream of pseudorandomly concatenated triplets with standard ending triplets (letter in blackbox), statistical deviant ending triplets (letter in blue box), physical deviants (letter in red box) and double deviants (letters in purple box). Physical deviants were generated by switching speaker, leading to a spatial location change of 60° in the azimuth plane.
Table 1.
Comparative view of demographic information between the two experiments.
Table 2.
Comparative view of experiment design details for the two experiments.
Interstimulus interval denotes the silent interval between the offset of one tone and the onset of the next one. SOAs denote the interval between the onset of one tone and the onset of the next one.
Table 3.
Predictability values for triplet endings.
Table 4.
Comparative view of methodological details for the two experiments.
Fig 2.
ERPs of statistical and physical deviants as recorded in the current study with non-isochronous sound presentation, and in the previous study [25] with isochronous sound presentation.
(A) Mean ERP waves for standards and statistical deviants and the difference (no sMMN) under non-isochronous as recorded at electrode Fz. The shaded area on the ERPs represents the SEM. (B) Mean ERP waves for standards and physical deviants, as recorded from the electrode FCz. The dotted rectangle indicates the time-window for statistical analysis (150–220 ms). (C) Isopotential map showing the scalp distribution of the location MMN over the time-window (150–220 ms). (D) The sMMN under isochronous (high temporal predictability) stimulation as captured at electrode Fz. The dotted rectangle indicates the time-window for statistical analysis (180–260 ms). (E) The location MMN under isochronous stimulation as captured at electrode FCz. (F) Isopotential maps showing the scalp distribution of the sMMN over the window (180–260 ms) and the location MMN over the window (150–220 ms). (G) Separate traces for the differences to statistical deviants under isochronous and non-isochronous stimulation as captured at electrode Fz. (H) Separate traces for the location MMN under isochronous and non-isochronous stimulation as captured at electrode FCz. (I) Both sMMN and location MMN amplitudes decline significantly under non-isochronous stimulation.