Abstract
The merging of information from different senses (i.e., multisensory integration) can facilitate information processing. Processing enhancements have been observed with signals that are irrelevant to the task at hand, and with cues that are non-predictive. Such findings are consistent with the notion that multiple sensory signals are sometimes integrated automatically. Multisensory enhancement has even been reported with stimuli that have been presented subliminally, though only with meaningful multisensory relations that have already been learned. The question of whether there exist cases where multisensory effects occur without either learning or awareness has, though, not been clearly established in the literature to date. Here, we present a case study of a patient with Posterior Cortical Atrophy, who was unable to consciously perceive visual stimuli with our task parameters, yet who nevertheless still exhibited signs of multisensory enhancement even with unlearned relations between audiovisual stimuli. In a simple speeded detection task, both response speed, and the variability of reaction times, decreased in a similar manner to controls for multisensory stimuli. These results are consistent with the view that the conscious perception of stimuli and prior learning are not always a prerequisite for multisensory integration to enhance human performance.
Highlights
Multisensory integration can lead to enhanced performance on many behavioural and cognitive tasks
While other unconscious multisensory effects have been documented for control participants (Cox and Hong 2015; Faivre et al 2014), it is important to note that they have only been found with previously learned multisensory relations [e.g., in adults, subliminally presented primes of well-learnt stimuli, such as auditory and visual digits can be integrated, but only if the task is first learned using conscious multisensory primes; (Faivre et al 2014)]
The present study further demonstrates that the task-relevance of signals can override prior learned semantic associations to enhance multisensory information processing as all of the participants, including controls, showed enhancements of a similar magnitude with congruent and incongruent multisensory stimuli
Summary
Multisensory integration can lead to enhanced performance on many behavioural and cognitive tasks. Multisensory integration is potentially important for remedial adaptation and plasticity following brain atrophy, and may provide an important vehicle for neurorehabilitation, for those patients with impaired perceptual awareness. In those patients with perceptual deficits, such as hemianopia and neglect, multisensory stimulation can effectively be used to enhance and alter perceptual awareness (e.g., Calamaro et al 1995; Frassinetti et al 2005; Leo et al 2008; Passamonti et al 2009; Soroker et al.1995). We evaluate a case where visual signals are not perceived, remaining unconscious, and multisensory relations unlearnt
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