A role for the inferior colliculus in multisensory speech integration

Abstract

Multisensory integration can occur at relatively low levels within the central nervous system. Recent evidence suggests that multisensory audio-visual integration for speech may have a subcortical component, as acoustic processing in the human brainstem is influenced by lipreading during speech perception. Here, stimuli depicting the McGurk illusion (a demonstration of auditory-visual integration using speech stimuli) were presented to a 12-year-old child (FX) with a circumscribed unilateral lesion of the right inferior colliculus. When McGurk-type stimuli were presented in the contralesional hemifield, illusory perception reflecting bimodal integration was significantly reduced compared with the ipsilesional hemifield and a group of age-matched controls. These data suggest a functional role for the inferior colliculus in the audio-visual integration of speech stimuli.

Distribution of eye position information in the monkey inferior colliculus

“…In this illusion, when subjects are presented with a video of a speaker pronouncing a syllable ("ga") matched with an auditory presentation of a different syllable ("ba"), they hear something that is a mix of the two ("da"). A recent case report of a patient with a unilateral IC lesion showed that the effect was reduced when stimuli were presented in the contralateral hemifield (Champoux et al 2006). These data directly implicate the IC in audiovisual integration.…”

Visual- and saccade-related signals in the primate inferior colliculus

“…Indeed, a recent study in a human patient with a unilateral lesion to the IC showed a reduction in the bimodal interactions of the McGurk effect when the stimuli were presented in the contralesional hemifield (37). Additional studies comparing the IC responses elicited by visual stimuli that are naturally associated with sounds with those elicited by visual stimuli that are normally silent may help elucidate the purpose of visual signals in the IC.…”

Auditory pathways fail to re-establish normal cortical activation patterns in response to binaural stimulation following a unilateral lesion of the inferior colliculus

“…Based on these results, it can be argued that these normal performances on simpler tasks can be attributed to some form of neural reorganization that may have taken place between the date of the lesion and the time of testing (approximately 2 years). However, other behavioural and electrophysiological results on subject FX showed deficits in a number of auditory tasks such as recognition of low-redundancy speech presented monaurally, pattern-recognition of tonal sequences, frequency discrimination, binaural separation, binaural integration, as well as sound-source localization in space and multisensory integration (Champoux et al, 2006(Champoux et al, , 2007a(Champoux et al, , 2007b. These deficits were particularly salient when stimuli were presented to the left ear (i.e., the ear contralateral to the lesion) as compared to the right ear.…”

“…The particular aspect of this case was that the lesion was circumscribed to the right IC (see Figure 1). FX's neurological status, audiometric profile and behavioural performance has been described in length elsewhere (see Champoux et al, 2006Champoux et al, , 2007aChampoux et al, , 2007b. In short, FX does not show any problems in recognizing acoustical stimuli (e.g., speech, music, or environmental) nor does he report any everyday life difficulty.…”