Abstract
When we actively interact with the environment, it is crucial that we perceive a precise temporal relationship between our own actions and sensory effects to guide our body movements. Thus, we hypothesized that voluntary movements improve perceptual sensitivity to the temporal disparity between auditory and movement-related somatosensory events compared to when they are delivered passively to sensory receptors. In the voluntary condition, participants voluntarily tapped a button, and a noise burst was presented at various onset asynchronies relative to the button press. The participants made either “sound-first” or “touch-first” responses. We found that the performance of temporal order judgment (TOJ) in the voluntary condition (as indexed by the just noticeable difference (JND)) was significantly better (M = 42.5 ms ± 3.8 SEM) than that when their finger was passively stimulated (passive condition: M = 66.8 ms ± 6.3 SEM). We further examined whether the performance improvement with voluntary action can be attributed to the prediction of the timing of the stimulation from sensory cues (sensory-based prediction), kinesthetic cues contained in voluntary action, and/or to the prediction of stimulation timing from the efference copy of the motor command (motor-based prediction). When three noise bursts were presented before the target burst with regular intervals (predictable condition) and when the participant’s finger was moved passively to press the button (involuntary condition), the TOJ performance was not improved from that in the passive condition. These results suggest that the improvement in sensitivity to temporal disparity between somatosensory and auditory events caused by the voluntary action cannot be attributed to sensory-based prediction and kinesthetic cues. Rather, the prediction from the efference copy of the motor command would be crucial for improving the temporal sensitivity.
Highlights
When we actively interact with the environment in everyday life, most of our body movements can generate impact sounds that provide fine temporal information regarding our body-environment interactions
We found that the voluntary action influenced the temporal sensitivity
While the observed just noticeable difference (JND) in the passive condition were comparable to those reported in previous studies (e.g., Zampini et al, 2005), the voluntary movement reduced the JND by 36% from that obtained in the passive condition (Figure 4A; the mean JND was 66.8 (±6.3 SEM) in the passive condition and 42.5 (±3.8 SEM) in the voluntary condition)
Summary
When we actively interact with the environment in everyday life, most of our body movements can generate impact sounds that provide fine temporal information regarding our body-environment interactions. No significant differences in JNDs for the temporal disparity of auditory-somatosensory events between the voluntary and involuntary movement conditions have been reported (Frissen et al, 2012; Hao et al, 2015), improvement (Nishi et al, 2014) and even deterioration (Hao et al, 2016) of the JNDs has been observed in the voluntary movement condition compared to passive and involuntary ones The reason for this inconsistency between the findings of the previous studies is unclear. The present study tried to dissociate the effects of the three components—sensory-based predictability of the timing of multisensory events, kinesthetic cues of body movements and motor-based prediction from the efference copy of a motor command—involved in voluntary movements that might improve multisensory temporal sensitivity (compared to that without body movements) when there is a strong causal relationship between the voluntary movements and the sensory events. We employed a temporal order judgment (TOJ) task for assessing the temporal sensitivity (Vroomen and Keetels, 2010)
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