The Temporal Window of Multisensory Integration under Competing Circumstances

Abstract

Our brain tends to integrate information from different sensory modalities when presented within the so-called temporal window of integration. Whereas other studies investigated this window using a single audio-visual event, we examine the effect of competing spatio-temporal circumstances. Participants saw nineteen luminance-modulating discs while hearing an amplitude modulating tone. The luminance-modulation of each disc had a unique temporal phase (between −380 and 380 ms; steps of 40 ms), one of which was synchronized with the tone. Participants were instructed to identify which disc was synchronized with the tone. The waveforms of auditory and visual modulations were either both sinusoidal or square. Under sine-wave conditions, participants selected disks with phase offsets indistinguishable from guessing. In contrast, under square-wave conditions, participants selected the correct disc (phase = 0 ms) with a high degree of accuracy. When errors did occur, they tended to decrease with temporal phase separation, yielding an integration window of ∼140ms. These results indicate reliable AV integration depends upon transient signals. Interestingly, spatial analysis of confusion density profiles indicate transient elements left and right of fixation are integrated more efficiently than elements above or below. This anisotropy suggests that the temporal window of AV integration is constrained by intra-hemsipheric competition.