Abstract
To maintain perceptual coherence, the brain corrects for discrepancies between the senses. If, for example, lights are consistently offset from sounds, representations of auditory space are remapped to reduce this error (spatial recalibration). While recalibration effects have been observed following both brief and prolonged periods of adaptation, the relative contribution of discrepancies occurring over these timescales is unknown. Here we show that distinct multisensory recalibration mechanisms operate in remote and recent history. To characterise the dynamics of this spatial recalibration, we adapted human participants to audio-visual discrepancies for different durations, from 32 to 256 seconds, and measured the aftereffects on perceived auditory location. Recalibration effects saturated rapidly but decayed slowly, suggesting a combination of transient and sustained adaptation mechanisms. When long-term adaptation to an audio-visual discrepancy was immediately followed by a brief period of de-adaptation to an opposing discrepancy, recalibration was initially cancelled but subsequently reappeared with further testing. These dynamics were best fit by a multiple-exponential model that monitored audio-visual discrepancies over distinct timescales. Recent and remote recalibration mechanisms enable the brain to balance rapid adaptive changes to transient discrepancies that should be quickly forgotten against slower adaptive changes to persistent discrepancies likely to be more permanent.
Highlights
To obtain a unified and precise percept in dynamic environments, the human brain integrates information across multiple sensory modalities
We use the ventriloquism aftereffect to distinguish whether control of timescales of multisensory recalibration is governed by a singular mechanism that grows in strength, or distinct mechanisms that gradually activate over time
Behavioural studies of unimodal sensory perception have supported the notion of distinct mechanisms by showing that several, potentially opposing, adaptation effects can be simultaneously maintained when they occur across different timescales, ranging from minutes to hours or even days[20,21,22]
Summary
To obtain a unified and precise percept in dynamic environments, the human brain integrates information across multiple sensory modalities. Behavioural studies of unimodal sensory perception have supported the notion of distinct mechanisms by showing that several, potentially opposing, adaptation effects can be simultaneously maintained when they occur across different timescales, ranging from minutes to hours or even days[20,21,22]. A previous study of rapid spatial adaptation by Bruns and Röder demonstrated that the ventriloquism aftereffect shifts from being frequency-independent to frequency-dependent with increasing durations of adaptation, from a single trial up to four trials[17] This suggests an adaptation process that is coupled to the timescales over which audio-visual discrepancies occur in the environment. These behavioural effects pertain to rapid adaptation to the very recent past, it remains unclear whether distinct or unitary recalibration mechanisms exist over longer timescales. If recalibration is controlled by distinct mechanisms operating at different timescales, aftereffects will initially be cancelled by the de-adaptation, but will subsequently reappear with further testing[21,25]
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