Numerous studies showed that, after adaptation to a leftward optical deviation, pseudoneglect behavior (overrepresentation of the left part compared to the right part of the space) becomes neglect-like behavior (overrepresentation of the right part compared to the left part of the space). Cognitive after-effects have also been shown in cognitive processes that are not intrinsically spatial in nature, but show spatial association as numbers or letters.The space-auditory frequency association (with low frequencies on the left and high frequencies on the right) raises the question of whether prism adaptation can produce aftereffects on auditory perception. We used a new experimental protocol, named the 'auditory interval bisection judgment', where participants had to estimate what limit of an auditory interval (low or high) a target frequency was closer to. We calculated the subjective auditory interval center. In pretest, there was a spontaneous bias of the subjective center of the auditory interval toward the lower limit. That was the first demonstration of pseudoneglect behavior in auditory frequency representation. ANOVA realized on all participants did not show significant results of prism adaptation, but a posteriori analyses on musicians showed that, after adaptation to a leftward optical deviation, there were more target frequencies perceived as closer to the lower limit of the auditory interval. This result corroborates the shift of the subjective center of the auditory interval toward high frequency limit. These innovative results are discussed in terms of putative neural substrates underpinning the transfer of visuomotor plasticity to auditory frequency perception.

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Objective: Prism adaptation was shown to modify auditory perception. Using a dichotic listening task, which assesses auditory divided attention, benefits of a rightward prism adaptation were demonstrated in neglect patients (i.e., a syndrome following right hemisphere brain damage) by reducing their left auditory extinction. It is currently unknown whether prism adaptation affects auditory divided attention in healthy subjects. In the present study, we investigated the aftereffects of prism adaptation on dichotic listening. Method: A sample of 47 young adults performed a dichotic listening task, in which pairs of words were presented with two words sounded simultaneously, one in each ear. Three parameters were measured: The percentage of recalled words, the percentage of correctly recalled words, and the laterality index (LI). Results: Prism adaptation to a leftward optical deviation (L-PA) significantly increased the overall percentage of recalled words ( p = .044) and that from the right ear ( p = .002), and the overall LI ( p = .049). Conclusions: For the first time, these findings demonstrate that L-PA produced an orientation of the auditory divided attention in favor of the right ear in healthy participants. This asymmetrical aftereffect provides a new argument in favor of the cross-modal dimension of prism adaptation, although an acclimatization effect of the dichotic listening task is also discussed. Our study opens up a new avenue for using prism adaptation in the field of auditory rehabilitation requiring a modulation of auditory attention. Key PointsQuestion: Does prism adaptation act on auditory divided attention in healthy people? Findings: Prism adaptation to a leftward optical deviation produces aftereffects on auditory divided attention in favor of the right ear. Importance: Prism adaptation produces auditory cross-modal aftereffects. Next Steps: Using prism adaptation in auditory rehabilitation requiring a modulation of auditory attention.

Sensorimotor aftereffects have been widely studied after lateral prism adaptation but not after vertical prism adaptation. It is thus well-known that lateral prism adaptation produces aftereffects on visuospatial representation and, recently, on auditory perception. This study aimed to explore the sensorimotor after-effects of vertical prism adaptation as well as its aftereffects on vertical visuospatial representation (Experiment 1) and on auditory frequency representation (Experiment 2). The experimental procedure was similar in both experiments: before and after prism adaptation to an upward or a downward optical deviation, healthy young participants performed an visual open-loop pointing task and a visual (Experiment 1) or an auditory (Experiment 2) perceptual bisection task. In the visual task, the participants had to indicate if they perceived the bisection as higher or lower than the true center of a line. In the auditory task, the participants had to indicate if they perceived the target auditory frequency closer to the low or the high limit of an auditory interval. For sensorimotor aftereffects, pointing errors were computed by means of a vertical touchscreen. For the perceptual bisection task, we measured the percentage of “down” (Experiment 1) or “low” responses (Experiment 2), and we computed the visual (Experiment 1) or the auditory (Experiment 2) subjective center for each participant. Statistical analyses were carried out separately for each optical deviation in each experiment. Sensorimotor aftereffects were observed in both experiments, in the opposite direction to the optical deviation (all ps < 0.01). No significant aftereffects occurred on visuospatial representation (all ps > 0.5), whereas the percentage of “low” responses and the auditory subjective center significantly increased after adaptation to a downward optical deviation (all ps < 0.05). Unlike lateral prism adaptation aftereffects that have been previously shown in both visuospatial horizontal representation and auditory frequency representation, aftereffects of vertical prism adaptation occurred in the auditory frequency representation but not in the vertical visuospatial representation. These results suggest that both vertical and lateral prism adaptations share a common substrate dedicated to the auditory modality (probably the temporal cortex), and that vertical adaptation does not act on the neural substrate of vertical visuospatial representation.