Poster #: 67
Topic: Memory and perception
Wednesday, Sep 9, 2015
The effects of frequency difference and ear-of-entry on auditory stream segregation and integration
1Institute of Behavioural Sciences, University of Helsinki, Helsinki, Finland
Auditory system constantly organises the sounds of auditory environment, integrating some sounds to the same auditory stream and segregating others to separate auditory streams. We investigated the effects of frequency difference and ear-of-entry on auditory stream integration and segregation. We recorded event-related potentials (ERP) while presenting the participants with tone pairs consisting of low and middle tone or middle and high tone in a repetitive sequence. To investigate the effect of frequency, the low, middle, and high tones were separated by 2, 7, or 16 semitones in three separate conditions. To investigate the effect of ear-of-entry, we compared the binaurally presented 7 semitone condition with ear-of-entry difference condition and mixed ear-of-entry condition. In ear-of-entry difference condition the low tones were presented to the right ear, the middle tones to both ears, and the high tones to the left ear. In mixed ear-of-entry condition the low, middle, and high tones were presented randomly to the right, to the left, or to both ears. Two types of deviant stimuli were used: omitting the second tone of a pair could serve as a deviant when the streams were integrated and frequency change in the middle tone could serve as a deviant when the streams were segregated. The results showed that large frequency difference promotes stream segregation whereas smaller frequency differences lead to stream integration. The organisation of streams was alternating between integration and segregation in ear-of-entry difference condition. The streams were segregated when the ear-of-entry was mixed.