Sensory loss enhances multisensory integration performance

Abstract

Auditory and visual sensory loss has repeatedly been shown to alter abilities in remaining sensory modalities. It is, however, unclear whether sensory loss also impacts multisensory integration; an ability that is fundamental for the perception of the world around us. We determined effects of olfactory sensory deprivation on multisensory perception by assessing temporal as well as semantic aspects of audio-visual integration in 37 individuals with anosmia (complete olfactory sensory loss) and 37 healthy, matched controls. Participants performed a simultaneity judgement task to determine the temporal binding window, and a multisensory object identification task with individually degraded, dynamic visual, auditory, and audio-visual stimuli. Individuals with anosmia demonstrated an increased ability to detect multisensory temporal asynchronies, represented by a narrowing of the audio-visual temporal binding window. Furthermore, individuals with congenital, but not acquired, anosmia demonstrated indications of greater benefits from bimodal, as compared to unimodal, stimulus presentation when faced with degraded, semantic information. This suggests that the absence of the olfactory sense alters multisensory integration of remaining senses by sharpening the perception of cross-modal temporal violations, independent of sensory loss etiology. In addition, congenital sensory loss may further lead to increased gain from multisensory, compared to unisensory, information. Taken together, multisensory compensatory mechanisms at different levels of perceptual complexity are present in individuals with anosmia.

Acquired olfactory loss alters functional connectivity and morphology

“…One could therefore hypothesize that a lack of olfactory input to these parietal multisensory areas may change the neuronal constellation and promote a more efficient multisensory-based integration of visual and auditory sensory modalities for individuals with anosmia. Measures assessing functional processing of multisensory stimuli were not acquired in the present study but we demonstrate that individuals with anosmia have stronger functional connectivity from the angular gyrus with areas associated with primary visual and taste processing, thus suggesting a functional reorganization that might facilitate improved multisensory processing, much like our past study demonstrated (Peter et al, 2019). Although it is worth noting that the demonstrated enhancement is of a multisensory nature (Peter et al, 2019) and that there is no evidence that anosmia facilitates improved acuity for unisensory visual or auditory stimuli, a clear demonstration of reduced acuity for unisensory taste (Gagnon et al, 2014;Gudziol et al, 2007;Landis et al, 2010) and trigeminal sensations (Frasnelli and Hummel, 2007;Hummel et al, 1996) in individuals with either congenital anosmia or olfactory dysfunction does, however, exist.…”

“…Past studies have demonstrated that individuals with anosmia are better at extracting information from multisensory stimuli (Peter et al, 2019) and we recently demonstrated functional gating between posterior piriform cortex and multisensory areas when processing multisensory stimuli (Lundström et al, 2018). Therefore, given the larger GM volume in the angular gyrus on the one hand, and the stronger connection between posterior piriform cortex and angular gyrus on the other, we next assessed whether there was a difference between groups in dFC from the angular gyrus.…”

Individual differences in multiple object tracking, attentional cueing, and age account for variability in the capacity of audiovisual integration

“…Recent research addressing the effects of anosmia, or the loss of olfaction, suggests that that the absence of the sense of smell heightens an individual's ability to integrate auditory and visual stimuli and detect multisensory temporal asynchronies, due in part to a narrower temporal binding window (Peter et al, 2019). Additionally, those who had been born with anosmia demonstrated a greater ability to distinguish asynchronies than those with acquired sensory loss (Peter et al, 2019). The current research focuses on the importance of individual differences in the capacity for audiovisual integration.…”

Posterior parietal cortex contributions to cross-modal brain plasticity upon sensory loss

“…Examples are visual cortex contributions to braille reading and echo localization in the blind [7,8]. The posterior parietal cortex (PPC) is multisensory in nature and is gaining attention as an important player in cross-modal plasticity [9].…”