Assessment of the role of the cochlear latency effect in lateralization of click sounds in humans

Abstract

Interaural time and intensity disparities (ITD and IID) are the two cues to sound lateralization. "Time-only" hypothesis claims that an IID is first converted to an interaural afferent delay (Delta t), and is then processed by the central ITD mechanism, rendering a separate IID processor unnecessary. We tested this hypothesis by assessing the contribution of the cochlear latency effect to the psychophysical ITD/IID trading ratio. Auditory brainstem responses (ABRs) were used to measure the interaural afferent delays (Delta ts) that developed with a 20/sec dichotic click train used in the trading experiment. Except for small IIDs at low loudness levels, the physiological Delta t delay produced by an IID was significantly smaller than the ITD psychophysically traded for the same IID. We concluded that the cochlear latency effect alone cannot explain the psychophysical ITD/IID trading ratios and a separate IID mechanism must be involved.

Aging effects on the binaural interaction component of the auditory brainstem response in the Mongolian gerbil: Effects of interaural time and level differences

“…A larger effect of ITD than of ILD could be explained by the trading ratio. In the auditory nerve a trading ratio of about 10 μs/dB was observed in single fiber recordings (Joris et al, 2008) which is close to the value of 20 μs/dB observed in human ABR (Özmen and Ungan, 2009). The electrophysiological trading ratio affecting the BIC being observed for an ILD range of up to 20 dB results in a similar ratio (20 μs/dB) as the cat ABR data (Ungan et al, 1997).…”

“…ILDs of the signal envelope could also result in ITDs due to the time-intensity trading in auditory nerve fibers that provide some timing information at high frequencies (Joris et al, 2008). The time-intensity trading also applies to broadband clicks in that it may well be that ITDs in the carrier and ITDs resulting from level differences (e.g., originating from level-dependent latencies in the auditory nerve, (Özmen and Ungan, 2009) are both processed by the LSO (Irvine et al, 2001; ) and no conclusion about the origin of the BIC can be derived from the relation between the BIC and ITD and ILD, respectively.…”

Psychophysics and neuronal bases of sound localization in humans

“…Meanwhile, a recent EEG study (Junius et al, 2007) on BAEP (peaking <10 ms from sound onset) and middle-latency auditory evoked potentials (MAEP, peaking <50 ms of sound onset) suggest that ITD and ILD are processed separately at the level of the brainstem and primary AC. Similar conclusions could be reached based on 80-Hz steady-state response (SSR) studies (Zhang et al, 2008) and BAEP measurements of the so-called cochlear latency effect (Ozmen et al, 2009). Interestingly, the study of Junius and colleagues also showed that, unlike the responses reflecting non-primary AC function (Callan et al, 2012; Palomäki et al, 2005), the BAEP and MAEP components were not larger for individualized 3D simulations containing all direction cues than for ITD/ILD.…”

“…In particular, the subcortical mechanisms of ITD processing are a topic of a debate, as the applicability of long-prevailing theories of interaural coindicence detection (Jeffress, 1948) to mammals has been recently challenged (McAlpine, 2005). Here, we will, however, concentrate on cortical mechanisms of sound localization that have intensively studied using human neuroimaging, in contrast to the relatively limited number of fMRI (Thompson et al, 2006) or EEG (Junius et al, 2007; Ozmen et al, 2009) studies on subcotrical activations to auditory spatial cues. On the same note, human neuropsychological (Adriani et al, 2003; Clarke et al, 2000; Clarke et al, 2002) and neuroimaging (Alain et al, 2001; Arnott et al, 2004; Bushara et al, 1999; De Santis et al, 2006; Huang et al, 2012; Kaiser et al, 2001; Maeder et al, 2001; Rämä et al, 2004; Weeks et al, 1999) studies have produced detailed information on networks contributing to higher-order cognitive control of auditory spatial processing beyond ACs, including posterior parietal ( e.g ., intraparietal sulcus) and frontal regions ( e.g ., premotor cortex/frontal eye fields, lateral prefrontal cortex).…”

Binaural Sound Localizer for Azimuthal Movement Detection Based on Diffraction

“…Connecting both areas and devising the acoustic localizer based on the understanding of the spatial hearing is considered as the third practical area of research. The application of the spatial hearing is distributed over a wide range of technologies including the 3D sound [6], medical diagnosis [7], architectural acoustics [8], and many other applications. The recent novel movement of the research can be described as designing the sound localizer which mimics the spatial hearing of animals with monaural or binaural auditory systems.…”