Interest and validity of the additive model in electrophysiological studies of multisensory interactions

Abstract

Fort, Marie-Hélène Giard. Interest and validity of the additive model in electrophysiological studies of multisensory interactions.

Auditory–Visual Multisensory Interactions in Humans: Timing, Topography, Directionality, and Sources

“…This criticism is circumvented in the present study by our analysis of trials requiring attention, but no motor response. Another criticism of studies using the additive model concerned the insufficient control of attention (Besle et al, 2004). Importantly, participants perform the same task for the three modalities (A, V, and AV) in the present study, and the static stimuli on which we focused our analyses here required attention (regardless of sensory modality) to attain a high level of performance.…”

“…Our analyses here are based on the application of an additive model to detect nonlinear neural response interactions, wherein the ERP in response to the AV S condition is contrasted with the summed ERPs in response to the A S and V S conditions (hereafter referred to as "pair" and "sum" ERPs, respectively). Such a model has been repeatedly applied in ERP and magnetoencephalography studies in humans (Miniussi et al, 1998;Giard and Peronnet, 1999;Foxe et al, 2000;Murray et al, 2001Murray et al, , 2005Molholm et al, 2002;Besle et al, 2004;Möttönen et al, 2004;Brefczynski-Lewis et al, 2009;Sperdin et al, 2009Sperdin et al, , 2010Raij et al, 2010) as well as electrophysiological investigations in nonhuman primates (Meredith and Stein, 1986;Stein and Meredith, 1993;Wallace et al, 1996;Wallace and Stein, 2007;Kayser et al, 2008). Despite its widespread application, this model nonetheless receives some criticism (Gondan and Röder, 2006), which has been refuted on theoretical and empirical grounds (Fort et al, 2002a;Besle et al, 2004).…”

Visual Activation and Audiovisual Interactions in the Auditory Cortex during Speech Perception: Intracranial Recordings in Humans

“…Alternatively, lip movements may have brought phonetic information that "preactivate" the auditory cortex; this auditory activation resulting from the visual input would stop to leave full resources to the sensory-specific (auditory) cortex to process the acoustic/phonetic features of the syllables more efficiently. Nevertheless, the "preprocessing" of the visual syllable would result in engaging less auditory resources from the auditory cortex (response decreases) to process the syllable (Besle et al, 2004a, Giard andPeronnet, 1999). In both cases, the suppression of visual activity might reflect a ceiling effect: the auditory cortex would be maximally activated by speech sounds, and there would be no possibility for an additional activation by lip movements once the sound starts being processed.…”

“…Before each block, one of the four syllables was designated as the target and the patient's task was to click on a mouse whenever he/she heard the target (auditory and audiovisual conditions). No response was required in the visual-only condition to avoid engaging unnatural and exaggerated attention to the visual modality (by trying to lip-read), compared with the other two conditions (Besle et al, 2004a). The target syllables were not used to compute the ERPs.…”

“…To test the existence of audiovisual interactions, we compared the ERP elicited by the audiovisual syllable with the sum of ERPs elicited by unimodal syllables between 0 and 200 ms (Besle et al, 2004a). We thus sought to test the null hypothesis that the bimodal trials were drawn from the same distribution as the distribution of the sum of auditory and visual trials.…”