by Frank Musiek, PhD
While coursing through the literature the other day I came across some relatively recent articles that reported on some recent research on the binaural interaction component or BIC. I was a bit surprised because the BIC’s popularity in the 1980’s seemed to have subsided for many years.
Therefore, I thought it appropriate to briefly comment on the BIC for the monthly Pathways and remind us all about the procedure and some of its research and clinical value.
Binaural Interaction Component and its Clinical Value
The BIC deals with evoked potentials and has been shown in the ABR, MLR and late or cortical potentials. The BIC is obtained recording auditory evoked potentials (AEPs) from each ear and a binaurally. The responses from each ear are summed to provided derived response. The binaural response is then subtracted from the summed response. Interestingly, the binaural response is slightly smaller in amplitude than the summed response and when subtracted form the summed response yields a waveform of its own — this derived waveform is termed the BIC (Figure 1). The explanation for the attenuation of the smaller binaural response is that there is binaural processing starting in the brainstem and continuing through the auditory system. This binaural processing is reflected by BICs for early, middle and late evoked potentials and likely reflects an inhibition in the system.
The BIC for the ABR appears for waves IV, V, and VI which makes sense since it is at the superior olivary complex (SOC) where input from both ears is first realized physiologically and a binaural interaction is possible.. The SOC contributes to Wave IV of the ABR and waves V and VI (when it can be obtained) also reflect this binaural interaction.
There are some critical anatomical/physiological findings that lend to our knowledge of the origin of the ABR BIC. In animals, the sectioning at midline disrupting the dorsal, intermediate and ventral stria, which input to the SOC, will negate the BIC. Also, it appears from multiple studies that damage to the SOC components – especially the trapezoid body will severely compromise the BIC.
Interaural time differences (ITD) are related to the ABR BIC. ITDs are well known to be one of the keys to localization as well as lateralization. As ITDs become greater the BICs reduce in amplitude reflecting an important link.
Give that the ABR BIC reflects physiological interaction at the brainstem level, has anatomical correlates, and that is could be marker of auditory localization abilities, it logically became an attractive tool for investigating central auditory function. In this regard there have been a few papers that have demonstrated the BIC may have some potential value for assessing integrity of the central auditory system.
One of the early and important papers by Pratt and colleagues using ABR BIC looked at individuals with brainstem lesions. In this study the ABR BIC was abnormal (by criteria) in a significant number of individuals. Though the number of participants in this study was moderately small, the BIC measure proved to be essentially as sensitive as other comparative measures used in the study. A couple other studies in regard to ABR or MLR BIC seem worth mentioning here. Two studies, one by Gropal & Pierel and one by Delb et al., both reveal similar findings. Children with auditory processing deficits showed significantly reduced or absent ABR BICs compared to control groups. In another study by Abdollahi et al. on children with APD the MLR BIC was absent or reduced by comparison to controls. Though these studies are indeed promising, more similar studies using the BIC with individuals with known central auditory lesions need to be done. Though in this brief communication, the MLR and Late potential BIC has not been discussed, these measures beg for more investigation. The ABR BIC would likely only be sensitive to auditory brainstem involvement, whereas MLR and cortical BICs may be sensitive to auditory cortical and subcortical compromise. More research along these lines would be most welcomed in the basic and clinical science community.
Future Use of BICs?
Though there is some promise for using evoked potential BICs to assess higher order auditory function, there remain some significant hurdles to clear. Peripheral hearing loss—especially asymmetrical hearing loss seems to be a problem.
Though some studies have been done, it appears that hearing loss remains a challenge. Perhaps the BIC should only be used in those with normal peripheral hearing thresholds? Again, this is a challenge that needs to be tackled with a strong research effort – but will this happen?
There seems to be a renewed interest in BIC with a scattering of relatively recent articles but is this trend enough to solve some lingering problems? – I certainly hope it is.
Readings…..
- Laumen G, Ferber AT, Klump GM, Tollin DJ. The Physiological Basis and Clinical Use of the Binaural Interaction Component of the Auditory Brainstem Response. Ear Hear. 2016 Sep-Oct;37(5):e276-e290
- Dobie RA, Berlin CI. Binaural interaction in brainstem-evoked responses. Arch Otolaryngol. 1979;105:391–398.
- Dobie RA, Norton SJ. Binaural interaction in human auditory evoked potentials. Electroencephalogr Clin Neurophysiol. 1980;49:303–313.
- Kamakshi G., & Pierel, K.,Binaural interaction component in children at risk for central auditory processing disorder, Published online: 12 Oct 2009
- Delb W, Strauss DJ, Hohenberg G, Plinkert PK. The binaural interaction component (BIC) in children with central auditory processing disorders (CAPD). Int J Audiol. 2003 Oct;42(7):401-12.
- Abdollahi FZ, Lotfi Y, Moosavi A, Bakhshi E. Binaural Interaction Component of Middle Latency Response in Children Suspected to Central Auditory Processing Disorder. Indian J Otolaryngol Head Neck Surg. 2019 Jun;71(2):182-185.
- Pratt H, Polyakov A, Aharonson V, Korczyn AD, Tadmor R, Fullerton BC, Levine RA, Furst M. Effects of localized pontine lesions on auditory brain-stem evoked potentials and binaural processing in humans. Electroencephalogr Clin Neurophysiol. 1998 Sep;108(5):511-20.
