Cortical auditory distance representation based on direct-to-reverberant energy ratio

Do sounds near the hand facilitate tactile reaction times? Four experiments and a meta-analysis provide mixed support and suggest a small effect size

“…This would fit with a large body of work on visual-tactile peripersonal space (Holmes 2013). However, there is little evidence of audiotactile peripersonal space in monkeys, and only a little is known about how the brain might compute auditory distance (Kolarik et al 2016;Kopco et al 2020). Furthermore, studies using non-spatial sounds (Ferri et al 2015a, b) found similar effects to those using virtual or free-field sounds, suggesting that auditory distance is irrelevant to generating these RT benefits of 'near' stimuli.…”

“…This is computationally the most difficult part, and evidence for the existence of such a detailed representation in the brain is scarce (Kolarik et al 2016). Auditory representations of distance based only on the direct-to-reverberant energy ratio seem possible in humans (Kopco et al 2020), but distance discrimination is difficult (i.e. the best forced-choice performance for frontal stimuli was around 80% correct), requires training, familiarity with the stimulus, and sufficient time to perceive room reverberations (likely > 500 ms).…”

“…This left-right disparity increases with proximity (Kolarik et al 2016). Distance-dependent modulations of behaviour with lateralised sounds may therefore reflect the brain's processing of sound intensity or frequency, rather than distance (Kopco et al 2020).…”

“…However, absolute perception of distance in the auditory domain is poor, biased, and ambiguous. When distance can be perceived, it is heavily dependent on the stimulus type, on the properties of the room that the listener is in, and requires sufficient time for the observer to perceive reverberation or temporal modulation of the stimulus; familiarity with the sound source is often required (Kolarik et al 2016;Kopco et al 2020). These properties of auditory distance perception are not helpful for a representation of peripersonal space that is hypothesised to respond quickly to unexpected stimuli, for example in defensive situations (Bufacchi and Iannetti 2018).…”

“…Since little is known about any unambiguous cues to absolute auditory distance, it remains unknown whether the brain can extract the information required to represent auditory-tactile peripersonal space. The likely cues are distance-dependent changes in inter-aural level differences, frequency spectra, or direct-toreverberant energy ratios (Kolarik et al 2016;Kopco et al 2020).…”