Defence of dissertation in the field of biomedical engineering, Anna Maria Alexandrou, M.Sc.
Exploring how speech is processed in the brain.
Anna Maria Alexandrou, M.Sc., will defend the dissertation "Neurophysiological correlates of producing and perceiving natural connected speech" on 29 January 2018 at 12 noon at the Aalto University School of Science. This dissertation examined, using magnetoencephalography, how the brain supports generation and comprehension of real-life speech.
Speech is an integral part of our everyday lives, yet the brain mechanisms that enable us to generate and understand speech with such ease and fluency remain largely unknown. The aim of this doctoral dissertation was to shed light to this riddle, through an extensive experiment in which real-life speaking and listening scenarios were simulated. Brain activity was collected using magnetoencephalography (MEG): a non-invasive technique that measures the magnetic fields that are produced by the firing of brain neurons.
It was found that both brain hemispheres are activated during speaking and listening to speech. This is a novel piece of evidence that challenges the vastly popular idea of left hemisphere dominance for speech functions. This shows that studying real-life speech use can complement previous knowledge that was mostly based on evidence from studies examining isolated words and sentences.
In addition, it was revealed that the listeners' neutral activity tracks the speech rhytmn, that is, the rate of linguistic information in heard speech, in both low-level auditory cortex and higher-level, more integrative, brain regions. Such tracking may help listeners to comprehend speech. Finally, this doctoral dissertation presents a new methodology for quantifying speech rhythm.
Overall, this doctoral dissertation offers new insights on how the brain supports human communication, and underlines the importance of using naturalistic experimental paradigms also in future studies. On a broader scale, these findings may find practical applications in clinical work, as well as in the domain of brain-computer interfaces.
Opponent: Professor Sophie Scott, University College London, United Kingdom
Custos: Professor Riitta Salmelin, Aalto University School of Science, Department of Neuroscience and Biomedical Engineering
Electronic dissertation: http://urn.fi/URN:ISBN:978-952-60-7801-4