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Keywords:

  • Event-related brain potentials;
  • Tone pattern;
  • Rhythm pattern;
  • Mismatch negativity;
  • N1;
  • N2

ABSTRACT

Fourteen subjects were run in paradigms designed to explore event-related brain potentials (ERPs) elicited by breaks in alternations in pitch or interstimulus interval. In the Pitch paradigm, tones of 500 Hz or 1000 Hz were presented in alternation at regular interstimulus intervals of 800 ms. In the Rhythm paradigm, a single tone, either 500 Hz or 1000 Hz, was presented at interstimulus intervals alternating between 400 ms and 800 ms. Breaks in the Pitch paradigm consisted of a single repetition of a pitch, and in the Rhythm paradigm of a single repetition of the 400-ms interstimulus interval. Breaks occurred with a 10% probability in both cases. Subjects read while stimuli were being presented.

A N210 wave of about 3.5 μV was elicited by breaks in pitch pattern but not by breaks in rhythm. That it was largest (most negative) frontally suggests that it was a type of mismatch negativity. Analysis of waveforms constructed by subtracting ERPs to standards from ERPs to breaks confirmed these results. Thus we conclude that the system triggering mismatch negativity can encode the temporal ordering of pitches.