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.

Brain Mechanisms of Audiotactile and Audiomotor Interactions

Gina Caetano

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Engineering Physics and Mathematics for public examination and debate in Auditorium F1 at Helsinki University of Technology (Espoo, Finland) on the 21st of December, 2007, at 12 noon.

Overview in PDF format (ISBN 978-951-22-9149-6)   [5258 KB]
Dissertation is also available in print (ISBN 978-951-22-9148-9)


This thesis focuses on audiotactile integration, brain areas activated by vibrotactile stimulation, transfer of vibrotactile information to motor output, and reactivity of the human primary motor and somatosensory cortices in action observation. Human experience of the outside world results from integration of information obtained simultaneously via multiple senses. Accumulating evidence, from studies in both primates and humans, suggests that integration between different sensory modalities also occurs at early stages of cortical processing, in areas classically considered as purely unisensory. In Study I we studied integration between auditory and somatosensory systems. We showed, in a loudness-matching task, that subjects chose lower intensities for the probe than for the reference tone, when auditory and vibrotactile stimuli were presented simultaneously.

In Studies II and III we explored brain areas involved in processing vibrotactile and tactile information, respectively. We showed that, besides primary and secondary somatosensory areas, auditory areas are also activated. In Study II we characterized the time course of brain activations and showed convergence of vibrotactile information to auditory areas. On the other hand, in Study III we identified, with good spatial accuracy, common neural substrates that process auditory and tactile information in auditory belt areas.

In Study IV we assessed whether frequency information transfers from touch to vocal utterance in normal-hearing female adults. We demonstrated that such information transfer occurs clearly between 150–400 Hz. Based on findings in Studies II and III, we hypothesized that this transfer may involve at least primary and secondary somatosensory and auditory areas. Our social skills rely on the capability to understand others. In the human brain, the mirror-neuron system matches observation and execution of actions. This system comprises at least the inferior frontal gyrus, premotor areas, primary motor cortex, and the inferior parietal lobule.

In Study V we investigated similarities in sensorimotor oscillatory activity between own, observed, and heard actions. We demonstrated that the primary motor cortex is activated before own and observed actions and stabilizes similarly. We also showed that rhythmic activity in the primary somatosensory cortex recovers later during own actions, which may be related to proprioceptive input and contribute to maintaining the sense of agency.

This thesis consists of an overview and of the following 5 publications:

  1. Schürmann M, Caetano G, Jousmäki V, and Hari R. Hands help hearing: Facilitatory audiotactile interaction at low sound-intensity levels. Journal of the Acoustical Society of America 2004, 115: 830-832.
  2. Caetano G and Jousmäki V. Evidence of vibrotactile input to human auditory cortex. NeuroImage 2006, 29: 15-28.
  3. Schürmann M, Caetano G, Hlushchuk Y, Jousmäki V, and Hari R. Touch activates human auditory cortex. NeuroImage 2006, 30: 1325-1331.
  4. Caetano G and Jousmäki V. Kenneth, what's the frequency? Helsinki University of Technology, Low Temperature Laboratory, Report TKK-KYL-018.
  5. Caetano G, Jousmäki V, and Hari R. Actor's and observer's primary motor cortices stabilize similarly after seen or heard motor actions. Proceedings of the National Academy of Sciences of the United States of America 2007, 104: 9058-9062.

Keywords: audiotactile integration, auditory, mirror-neurons, motor, somatosensory

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© 2007 Helsinki University of Technology

Last update 2011-05-26