Browsing by Author "Väntänen, Jani"

Objectives. Perception of auditory pitch can be divided in to two dimensions of height and chroma. Tones of the same chroma, one or more octave intervals apart, sound similar. The octave interval is defined as the doubling of a tones fundamental frequency. However, in humans the perceptual octave slightly exceeds its mathematical counterpart. The objective of this study was to clarify the neural underpinnings responsible for the subjective experience of chroma and the enlarged octave. Methods. During all experiments adapter tones followed by probing tones were sequentially presented to participants (n=18). Adapter tones were used to activate neural populations and probing tones were used for measuring amplitude reductions (adaptation) in EEG derived event related potentials (ERPs) signalling overlapping neural population responses to adapter and probing tones. Participants were divided in to two groups with either sine tones or complex tones as adapters. 7 pitch separations between adapter and probe were used. Differences between different interval ERPs and effects of musical proficiency in both groups were analysed with mixed repeated measures analyses of variance. Measurements were fitted to a combined sinusoidal and linear pitch helix function. Source magnitude estimation was calculated to investigate hemispheric asymmetry. Results and conclusions. There was greater neural overlap between tones sharing the same chroma compared to tones one semitone apart. Periodicity independent adaptation indicated that pitch is not co-represented with stimulus spectrum in the human auditory cortex. Source magnitude analyses showed that N1 responses were stronger on the right auditory cortex. P2 amplitude showed stronger adaptation to enlarged octave intervals in comparison to exact mathematical octave intervals.