Cortical responses to a new dichotic pitch
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1
Aston University, United Kingdom
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2
Institute of Opthalmology, United Kingdom
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3
VU University Medical Center, Netherlands
Evoked-response beamformer analysis (ER-SAM) was used to explore cortical responses to a rapid interaural phase-modulation of narrow-band noise, which produces a newly-described auditory pitch. Whole-head MEG data were collected while participants listened to 100 exemplars of a 1-second noise stimulus (250-Hz bandwidth, centred on 500 Hz), where the pitch-eliciting modulation (60-Hz dichotic FM) was introduced 500 ms from sound onset. One hundred exemplars of a control stimulus where the same FM was diotic were interleaved with the dichotic stimuli. There was a variable ISI of at least 500 ms. Beamformer weights were computed for a 5 to 25 Hz frequency band over two separate 200-ms time windows centred on the evoked responses of interest; the N1-P2 complex at sound onset; and on the pitch onset response which occurred, for this stimulus, approximately 200 ms after FM-onset. The ER-SAM analysis yielded volumetric maps showing spectral power in the average dataset at the time of the peak in the evoked responses. Evoked-response time series were also reconstructed for the peak voxels of interest. For most participants the source of the pitch-onset-response was in planum temporale, just posterior to that for the peak of the N1-P2 onset response in Heschl's gyrus. The responses to the dichotic FM were significantly stronger than in the control condition, supporting our hypothesis that the pitch is a binaural phenomenon. The source in planum temporale is similar to that observed with fMRI for another binaural pitch, 'Huggins pitch', but differs from previous MEG reports for the source of a monaural temporal pitch. There was a strong hemispheric asymmetry which reflected behavioural observations that the pitch was strongly and consistently lateralised. This study contributes to our understanding of binaural pitch perception and provides evidence that MEG responses to pitch may differ depending on how the pitch is elicited.
Conference:
Biomag 2010 - 17th International Conference on Biomagnetism , Dubrovnik, Croatia, 28 Mar - 1 Apr, 2010.
Presentation Type:
Poster Presentation
Topic:
Sensory Processing and Functional Connectivity
Citation:
Witton
C,
Henning
BG and
Hillebrand
A
(2010). Cortical responses to a new dichotic pitch.
Front. Neurosci.
Conference Abstract:
Biomag 2010 - 17th International Conference on Biomagnetism .
doi: 10.3389/conf.fnins.2010.06.00210
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Received:
30 Mar 2010;
Published Online:
30 Mar 2010.
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Correspondence:
Caroline Witton, Aston University, Birmingham, United Kingdom, c.witton@aston.ac.uk