Browsing by Author "Sams, Mikko E."

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    Effect of attentional load on audiovisual speech perception: Evidence from ERPs
    (2014-07-15) Alsius, Agnès; Möttönen, Riikka; Sams, Mikko E.; Soto-Faraco, Salvador; Tiippana, Kaisa; Department of Neuroscience and Biomedical Engineering
    Seeing articulatory movements influences perception of auditory speech. This is often reflected in a shortened latency of auditory event-related potentials (ERPs) generated in the auditory cortex. The present study addressed whether this early neural correlate of audiovisual interaction is modulated by attention. We recorded ERPs in 15 subjects while they were presented with auditory, visual, and audiovisual spoken syllables. Audiovisual stimuli consisted of incongruent auditory and visual components known to elicit a McGurk effect, i.e., a visually driven alteration in the auditory speech percept. In a Dual task condition, participants were asked to identify spoken syllables whilst monitoring a rapid visual stream of pictures for targets, i.e., they had to divide their attention. In a Single task condition, participants identified the syllables without any other tasks, i.e., they were asked to ignore the pictures and focus their attention fully on the spoken syllables. The McGurk effect was weaker in the Dual task than in the Single task condition, indicating an effect of attentional load on audiovisual speech perception. Early auditory ERP components, N1 and P2, peaked earlier to audiovisual stimuli than to auditory stimuli when attention was fully focused on syllables, indicating neurophysiological audiovisual interaction. This latency decrement was reduced when attention was loaded, suggesting that attention influences early neural processing of audiovisual speech. We conclude that reduced attention weakens the interaction between vision and audition in speech.
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    Gaze-direction-based MEG averaging during audiovisual speech perception
    (2010-03-08) Hirvenkari, Lotta; Jousmäki, Veikko; Lamminmäki, Satu; Saarinen, Veli-Matti; Sams, Mikko E.; Hari, Riitta; Department of Neuroscience and Biomedical Engineering
    To take a step towards real-life-like experimental setups, we simultaneously recorded magnetoencephalographic (MEG) signals and subject’s gaze direction during audiovisual speech perception. The stimuli were utterances of /apa/ dubbed onto two side-by-side female faces articulating /apa/ (congruent) and /aka/ (incongruent) in synchrony, repeated once every 3 s. Subjects (N = 10) were free to decide which face they viewed, and responses were averaged to two categories according to the gaze direction. The right-hemisphere 100-ms response to the onset of the second vowel (N100m’) was a fifth smaller to incongruent than congruent stimuli. The results demonstrate the feasibility of realistic viewing conditions with gaze-based averaging of MEG signals.
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    Gaze-direction-based MEG averaging during audiovisual speech perception
    (Frontiers Media SA, 2010) Hirvenkari, Lotta; Jousmäki, Veikko; Lamminmäki, Satu; Saarinen, Veli-Matti; Sams, Mikko E.; Hari, Riitta; Neurotieteen ja lääketieteellisen tekniikan laitos; Department of Neuroscience and Biomedical Engineering; Perustieteiden korkeakoulu; School of Science
    To take a step towards real-life-like experimental setups, we simultaneously recorded magnetoencephalographic (MEG) signals and subject’s gaze direction during audiovisual speech perception. The stimuli were utterances of /apa/ dubbed onto two side-by-side female faces articulating /apa/ (congruent) and /aka/ (incongruent) in synchrony, repeated once every 3 s. Subjects (N = 10) were free to decide which face they viewed, and responses were averaged to two categories according to the gaze direction. The right-hemisphere 100-ms response to the onset of the second vowel (N100m’) was a fifth smaller to incongruent than congruent stimuli. The results demonstrate the feasibility of realistic viewing conditions with gaze-based averaging of MEG signals.