Do not throw out the baby with the bath water: Choosing an effective baseline for a functional localizer of speech processing

Nadav Stoppelman, Tamar Harpaz, Michal Ben-Shachar

Research output: Contribution to journalArticlepeer-review

27 Scopus citations

Abstract

Speech processing engages multiple cortical regions in the temporal, parietal, and frontal lobes. Isolating speech-sensitive cortex in individual participants is of major clinical and scientific importance. This task is complicated by the fact that responses to sensory and linguistic aspects of speech are tightly packed within the posterior superior temporal cortex. In functional magnetic resonance imaging (fMRI), various baseline conditions are typically used in order to isolate speech-specific from basic auditory responses. Using a short, continuous sampling paradigm, we show that reversed ("backward") speech, a commonly used auditory baseline for speech processing, removes much of the speech responses in frontal and temporal language regions of adult individuals. On the other hand, signal correlated noise (SCN) serves as an effective baseline for removing primary auditory responses while maintaining strong signals in the same language regions. We show that the response to reversed speech in left inferior frontal gyrus decays significantly faster than the response to speech, thus suggesting that this response reflects bottom-up activation of speech analysis followed up by top-down attenuation once the signal is classified as nonspeech. The results overall favor SCN as an auditory baseline for speech processing.

Original languageEnglish
Pages (from-to)211-222
Number of pages12
JournalBrain and Behavior
Volume3
Issue number3
DOIs
StatePublished - May 2013

Funding

FundersFunder number
Seventh Framework Programme231029

    Keywords

    • Functional localizer
    • Reversed speech
    • Signal correlated noise
    • Speech perception
    • fMRI

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