Lateralization and Binaural Interaction of Middle-Latency and Late-Brainstem Components of the Auditory Evoked Response

Abstract

We used magnetoencephalography to examine lateralization and binaural interaction of the middlelatency and late-brainstem components of the auditory evoked response(the MLR and SN10, respectively). Click stimuli were presented either monaurally, or binaurally with left-or right-leading interaural time differences (ITDs). While early MLR components, including the N19 and P30, were larger for monaural stimuli presented contralaterally (by approximately 30 and 36% in the left and right hemispheres, respectively), later components, including the N40 and P50, were larger ipsilaterally. In contrast, MLRs elicited by binaural clicks with left-or right-leading ITDs did not differ. Depending on filter settings, weak binaural interaction could be observed as early as the P13 but was clearly much larger for later components, beginning at the P30, indicating some degree of binaural linearity up to early stages of cortical processing. The SN10, an obscure late-brainstem component, was observed consistently in individuals and showed linear binaural additivity. The results indicate that while the MLR is lateralized in response to monaural stimuli-and not ITDs-this lateralization reverses from primarily contralateral to primarily ipsilateral as early as 40ms post stimulus and is never as large as that seen with fMRI.

Attentional Modulation of Envelope-Following Responses at Lower (93–109 Hz) but Not Higher (217–233 Hz) Modulation Rates

“…Based on evidence from ECoG showing cortical frequency-following in Heschl’s gyrus up to but not beyond 200 Hz (Brugge et al 2009 ; Nourski et al 2013 ; Behroozmand et al 2016 ) and recent MEG (Coffey et al 2016 ) and EEG (Coffey et al 2017 ) studies showing that the generators of the frequency-following response at 98 Hz most likely include cortex, we suspect that the observed dissociation might arise from cortical contributions to EFRs at the lower frequencies we tested in Experiment 1 and not at the higher frequencies we tested in Experiment 2. Although less likely, another possibility is that different findings at higher- and lower-modulation frequencies reflect the contribution of different combinations of brainstem generators to EFRs (see Marsh et al 1974 ; Dykstra et al 2016 ). The current results add to the growing literature by demonstrating that the most popular method for recording EFRs—EEG—is sensitive to different neural processes at frequencies above and below 200 Hz, within the range of frequencies at which EFRs are typically assumed to reflect brainstem processes.…”

Distinct Correlation Structure Supporting a Rate-Code for Sound Localization in the Owl’s Auditory Forebrain

“…Whereas maps have been associated to place code, a rate code has been suggested to explain the lack of it ( Konishi, 2003 ; Schnupp and Carr, 2009 ; Grothe et al, 2010 ). Responses in the forebrain are reminiscent of the two-channel rate code proposed for rodents ( McAlpine et al, 2001 ; Grothe et al, 2010 ) and humans ( Briley et al, 2013 ; Derey et al, 2016 ; Dykstra et al, 2016 ; McLaughlin et al, 2016 ). Thus, our findings may generalize to other species.…”

Aging alters across-hemisphere cortical dynamics during binaural temporal processing

“…Binaural coding and contralateral bias may also be reflected in the binaural interaction component (BIC); a derived measure that can be computed from the auditory brainstem response (ABR), middle latency response (MLR), or the cortical auditory evoked potential (CAEP) ( Dobie and Berlin, 1979 ; McPherson and Starr, 1993 ; Fowler and Horn, 2012 ; Van Yper et al, 2015 ; Dykstra et al, 2016 ; Laumen et al, 2016 ; Sammeth et al, 2020 ). The BIC is a difference waveform obtained by subtracting the algebraic sum of monaural responses to isolated left and right ear stimulation from the binaural response [B–(L + R)] or by computing the converse [(L + R)–B] ( McPherson and Starr, 1993 ; Van Yper et al, 2015 ).…”