Postersession 1
Poster #: 73
Topic: MMN across modalities
Wednesday, Sep 9, 2015
1st floor

Is the level of passive attention entrained by the rhythm of stimulation?

Pekcan Ungan1 & Hakan Karsilar2

1Biophysics, Koc University School of Medicine, Istanbul, Turkey
2Department of Psychology, Koc University,Graduate School of Social Sciences and Humanities, Istanbul, Turkey

There are studies reporting larger amplitudes for mismatch negativities (MMNs) recorded with constant inter-stimulus intervals (ISIs) than those with randomized ISIs. This would indicate an advantage of rhythmicity in a stimulus sequence for the passive attention mechanism. However, there are others reporting similar or larger amplitude MMNs recorded with randomized ISIs. To clarify this issue, we tested the hypothesis that the level of passive attention is so entrained by the rhythm of stimulation that it is maximized around the expected occurrence times of rhythmic standards.

Standard 1000 Hz tone-pips were presented with 800 ms ISIs. On average, every 7th standard was randomly replaced by a deviant stimulus which differed either in pitch (1200 Hz), or timing (ISI=500 ms), or in both. Event-related responses to standard (RS) and three deviant stimuli [pitch (RP), timing (RT), and pitch & timing (RPT), respectively] were recorded from reading subjects, and the waveforms of the MMNs to on-time and early pitch deviances were calculated as follows as grand averages: “MMN(800ms)=RP–RS” and “MMN(500ms)=RPT–RT”.

The MMN(800ms) elicited by pitch deviances occurring at times suggested by standard ISIs and the MMN(500ms) elicited by substantially earlier pitch deviances were found to have similar amplitudes.

Taking the MMN amplitude as an index for the level of passive attention and assuming the additivity of MMNs to changes in different auditory dimensions, this finding speaks against the hypothesis that the level of passive attention is entrained by the rhythm of stimulation.