Neural responses to uninterrupted natural speech can be extracted with precise temporal resolution

Authors

  • Edmund C. Lalor,

    1. Trinity College Institute of Neuroscience and
    2. Centre for Bioengineering, Trinity College Dublin, Dublin 2, Ireland
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  • John J. Foxe

    1. Trinity College Institute of Neuroscience and
    2. The Cognitive Neurophysiology Laboratory, Children’s Evaluation and Rehabilitation Center, Departments of Pediatrics and Neuroscience, Albert Einstein College of Medicine, 1410 Pelham Parkway South, Bronx, New York 10461, USA
    3. Cognitive Neurophysiology Laboratory, Nathan S. Kline Institute for Psychiatric Research, Orangeburg, NY 10962, USA
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Dr Edmund C. Lalor, 1Trinity College Institute of Neuroscience, as above. Dr J. Foxe, 3The Cognitive Neurophysiology Laboratory, as above.
E-mail: edlalor@tcd.ie or foxe@nki.rfmh.org

Abstract

The human auditory system has evolved to efficiently process individual streams of speech. However, obtaining temporally detailed responses to distinct continuous natural speech streams has hitherto been impracticable using standard neurophysiological techniques. Here a method is described which provides for the estimation of a temporally precise electrophysiological response to uninterrupted natural speech. We have termed this response AESPA (Auditory Evoked Spread Spectrum Analysis) and it represents an estimate of the impulse response of the auditory system. It is obtained by assuming that the recorded electrophysiological function represents a convolution of the amplitude envelope of a continuous speech stream with the to-be-estimated impulse response. We present examples of these responses using both scalp and intracranially recorded human EEG, which were obtained while subjects listened to a binaurally presented recording of a male speaker reading naturally from a classic work of fiction. This method expands the arsenal of stimulation types that can now be effectively used to derive auditory evoked responses and allows for the use of considerably more ecologically valid stimulation parameters. Some implications for future research efforts are presented.

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