The Role of Attention in Audiovisual Speech Integration: Evidence from ERPs

Agnès Alsius, Cognitive Neuroscience Group, Parc científic de Barcelona,Departament de Psicologia Bàsica Universitat de Barcelona

Abstract
Behavioural studies have shown that audiovisual integration of speech can be influenced by attentional manipulations (Tiippana et al., 2004; Alsius et al., 2005). On the other hand, recent event-related potential (ERP) studies have shown temporal facilitation and amplitude reduction of the auditory N1 to audiovisual speech compared with that to acoustic speech (Klucharev et al., 2003; Besle et al., 2004; Van Wassenhove et al., 2005). The goal of the present ERP study was to ascertain whether neural correlates of audiovisual speech integration can be modulated by manipulating attention. ERPs were recorded while participants identified spoken syllables presented auditorily, visually, or audiovisually (incongruent “McGurk” stimuli). Attention was manipulated by introducing a dual task paradigm where, in addition to the syllable identification task, participants were required to perform a concurrent unrelated visual search task. This attentional manipulation was reflected as a decrement in the percentage of the visually influenced responses to audiovisual stimuli reported by participants (i.e. a weaker McGurk effect). We also confirmed the effect of visual speech on the auditory N1 latency and amplitude and found a trend to a smaller effect during the dual task condition, suggesting that attention might play a role in early neural processing of audiovisual speech.

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