Auditory and visual object processing in olfactory cortex of individuals with life-long olfactory deprivation

Abstract

The traditional view of modality-specific brain organization has been challenged by demonstrations of cross-modal processing, i.e. the activation of sensory cortex by atypical sensory input. An alternative theory suggests that rather than specializing simply in different sensory modalities, different parts of the cortex can specialize in different types of tasks. We recently addressed this question in the olfactory domain, showing that in normosmic individuals, the primary olfactory cortex (piriform cortex) responds to unimodal auditory and visual objects, regardless of how strongly they are associated with an odor. Here, we assess whether previous olfactory experience is a prerequisite for this cross-modal processing in the piriform cortex, using a unique group of individuals born without a sense of smell (congenital anosmia; CA; n = 30). First, we were able to confirm the presence of clear visual and auditory activations in the piriform cortex of these sensory deprived individuals. As compared to normosmic controls (n = 30), these activations and associated functional connectivity, both within the piriform cortices and between piriform cortex and other regions, were altered in a modality dependent way. Our results show that life-long absence of olfactory input does not impede cross-modal activations by visual and auditory objects in the piriform cortex and are compatible with the idea of a task-based rather than modality-specific organization of this brain region.