The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Measures and Models of Top-Down Influences in the Human Auditory Cortex

Jaakko Kauramäki

Doctoral dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the School of Science for public examination and debate in Auditorium of Department of Biomedical Engineering and Computational Science at the Aalto University School of Science (Espoo, Finland) on the 16th of May 2012 at 12 noon.

Overview in PDF format (ISBN 978-952-60-4620-4)   [1378 KB]
Dissertation is also available in print (ISBN 978-952-60-4619-8)

Abstract

Our senses rapidly adapt to the sensory information and task requirements. These short-term, plastic changes especially in the central nervous system are necessary for goal-directed and active behavior. Nevertheless, partly due to methodological limitations, the neural mechanisms underlying improved perception during selective attention are not well understood. For instance, human auditory cortex activity is enhanced while engaging in an auditory task, but whether such enhancement involves a larger-extend or a more specific response from a sharply tuned neuronal population remains vague. In addition to unimodal attention effects, our senses can influence each others' processing. Seeing a person articulate can both enhance and modify the perception of acoustic speech and even induce activation in the auditory areas. The goal of the Thesis was to study the neural basis of these auditory cortex modulations both due to selective attention and cross-modal interactions while lipreading.

This Thesis consists of a series of four studies where the brain activity was recorded with electroencephalography (EEG) and its magnetic counterpart, magnetoencephalography (MEG). The results show that 1) evoked responses mainly from the secondary auditory areas were rapidly enhanced by a feature-specific manner during a discrimination task, where bottom-up and top-down processing were modified by stimulus and task design, 2) lipreading task suppressed auditory-cortex responses both generally and specifically in the case when sound was related to the articulatory gestures, and 3) lipreading and covert speech production tasks dynamically suppressed auditory cortex reactivity, possibly via an efference copy signal from the speech-production system.

Together, these studies expand the knowledge on how the human auditory cortex function is modulated under top-down influence. The modulations due to selective attention and cross-modal interactions while lipreading are opposite at the level of evoked responses: selective attention enhances and lipreading suppresses the responses, but both effects can be feature-selective. The results show that the auditory system is highly dependent on the current task requirements, showing adaptive and goal-dependent functioning.

This thesis consists of an overview and of the following 4 publications:

  1. Kauramäki, J., Jääskeläinen, I. P., and Sams, M. Selective attention increases both gain and feature selectivity of the human auditory cortex. PLoS ONE, 2(9): e909, September 2007. © 2007 by authors.
  2. Kauramäki, J., Jääskeläinen I. P., Hänninen, J. L., Auranen, T., Nummenmaa, A., Lampinen, J., Sams, M. Dual-stage adaptive filtering of sounds during selective attention. PLoS ONE, Submitted, December 2011. © 2011 by authors.
  3. Jääskeläinen, I. P., Kauramäki, J., Tujunen, J., and Sams, M. Formant transition specific adaptation by lipreading of left auditory cortex N1m. NeuroReport, 19(1): 93-97, January 2008. © 2008 Wolters Kluwer Health and © 2008 Lippincott Williams & Wilkins. By permission.
  4. Kauramäki, J., Jääskeläinen, I. P., Hari, R., Möttönen, R., Rauschecker, J. P., and Sams, M. Lipreading and covert speech production similarly modulate human auditory-cortex responses to pure tones. Journal of Neuroscience, 30(4): 1314-1321, January 2010. © 2010 by authors.

Keywords: electroencephalography, magnetoencephalography, top-down, attention, lipreading, human brain, auditory system, perception

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Last update 2014-03-21