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TU Berlin

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Modulation of P3a and P3b by varying quality of acoustic speech signals

LOCATION:  TEL, Auditorium 3 (20th floor), Ernst-Reuter-Platz 7, 10587 Berlin

Date/Time: 14.11.2016, 14:15-15:00

SPEAKER: Stefan Uhrig (TU Berlin)

ABSTRACT:

Quality of transmitted speech can be decomposed into three perceptual dimensions: Noisiness, coloration and discontinuity. The present study investigated whether degradation of single perceptual dimensions affects P3a and P3b characteristics. Both subcomponents served as neurophysiological indicators of different implicit processes during human quality formation: Occurrence of the earlier P3a was associated with a perceptual anticipation and matching process, occurrence of the later P3b with memory operations due the presence of a task-relevant stimulus event. Subjects (N = 24) performed an active three-stimulus oddball task with minimal stimulus sets according to practical guidelines for physiological quality assessment, meanwhile their electrical brain activity was recorded by EEG. Analyses of P300-related activity at channel Cz indicated the existence of different internal references for degraded vs. high-quality stimulus contexts as well as individual degradation classes. However, modulation of P3a and P3b parameters (peak amplitude, peak latency) also depended on the task relevance of the eliciting stimulus event. Visual characteristics of ERP waveforms for degraded stimuli as well as behavioral responses corresponded closely with their subjective quality ratings (ACR, CCR). Further evidence is needed to clarify if different internal quality-related processes are dissociable within the oddball paradigm.

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