We investigate how continuous speech is represented in human auditory cortex. We use magnetoencephalography (MEG) to record the neural responses of listeners to natural, continuous speech, in a variety of auditory scenes. Systems analysis, which mathematically compares a speech signal to its evoked cortical responses, allows us to determine the cortical representations of the speech. Interestingly, the cortical reprsentation allows the time-varying envelope of the speech to be reconstructed from the observed neural response to the speech. We find that cortical representations of continuous speech are very robust to interference from competing speakers, and many other kinds of noise, consistent with our ability to understand speech even in a noisy room (the "Cocktail Party" problem). Indeed, individual neural representations of the speech of both the foreground and background speaker are observed, with each being selectively time-locked to the rhythm of the corresponding speech, but the with the foreground speech represented more faithfully than the background. Finally, we show how these cortical represenations of speech are affected by aging.
Biography
Jonathan Simon joined the Electrical and Computer Engineering Department in January 2001 and the Biology Department in July 2002. He was an affiliate faculty member of the Institute for Systems Research until 2013, when he received an ISR joint appointment. His expertise is applied and theoretical neuroscience. He earned his doctorate in physics from the University of California, Santa Barbara, and did postdoctoral research in theoretical general relativity (University of Wisconsin-Milwaukee, and University of Maryland-College Park) before embracing the field of neuroscience.
Simon is co-director of the Computational Sensorimotor Systems Laboratory (CSSL) with ECE/ISR professor Timothy Horiuchi. CSSL focuses on the investigation, modeling and implementation of biological sensorimotor systems for both scientific and engineering purposes. Simon's research focuses on neural processing in the brain's auditory system, from specialized processing found only in humans (used in speech processing) to generalized processing found in most mammals, including sound localization.