Phantom perception as a Bayesian Inference problem - a pilot study.

Tinnitus is the perception of a sound in the absence of an external source. Although the role of the auditory system is well investigates, there is a gap in how multisensory signals are integrated to produce a single percept in tinnitus. Here, we train participants to learn a new sensory environment by associating a cue with a target signal that varies in perceptual threshold. In the test phase, we present only the cue to see if the person perceives an illusion of the target signal. We perform two separate experiments to observe the behavioural and electrophysiological responses to the learning and test phases in (i) healthy young adults and (ii) people with continuous subjective tinnitus and matched controls. We observed that in both parts of the study, the percentage of false alarms was negatively correlated with the 75% detection threshold. Additionally, the perception of an illusion goes together with increased evoked response potential in frontal regions of the brain. In patients with tinnitus, we observe no significant difference in behavioural or evoked response in the auditory paradigm, whereas patients with tinnitus were more likely to report false alarms going together with increased evoked activity during the learning and test phases in the visual paradigm. This impresses the importance of integrity of sensory pathways in multisensory integration and how this process may be disrupted in people with tinnitus. Furthermore, the current study also presents preliminary data supporting evidence that tinnitus patients maybe building stronger perceptual models.