Recalibration of auditory space following milliseconds of cross-modal discrepancy.

Basic features of objects and events in the environment such as timing and spatial location are encoded by multiple sensory modalities. This redundancy in sensory coding allows recalibration of one sense by other senses if there is a conflict between the sensory maps (Radeau and Bertelson, 1974; Zwiers et al., 2003; Navarra et al., 2009). In contrast to motor or sensorimotor adaptation, which can be relatively rapid, cross-sensory recalibration (the change in an isolated sensory representation after exposure to conflicting cross-modal information) has been reported only as a result of an extensive amount of exposure to sensory discrepancy (e.g., hundreds or thousands of trials, or prolonged durations). Therefore, sensory recalibration has traditionally been associated with compensation for permanent changes that would occur during development or after traumatic injuries or stroke. Nonetheless, the dynamics of sensory recalibration is unknown, and it is unclear whether prolonged inconsistency is required to trigger recalibration or whether such mechanisms are continuously engaged in self-maintenance. We show that in humans recalibration of perceived auditory space by vision can occur after a single exposure to discrepant auditory-visual stimuli lasting only a few milliseconds. These findings suggest an impressive degree of plasticity in a basic perceptual map induced by a cross-modal error signal. Therefore, it appears that modification of sensory maps does not necessarily require accumulation of a substantial amount of evidence of error to be triggered, and is continuously operational. This scheme of sensory recalibration has many advantages. It only requires a small working memory capacity, and allows rapid adaptation to transient changes in the environment as well as the body.