A similar

argument can be put forward against the theory

A similar

argument can be put forward against the theory that well-timed (phase locked), contralateral inhibition originating from the MNTB delays the time point at which the action potential threshold is reached (Brand et al., 2002; Pecka et al., 2008). This theory provides an elegant explanation for the observation that best ITDs typically show a bias for contralateral lead, which we also observed in the present study. This theory also predicts a significant phase-dependent influence of the sound from one ear on the response to the sound presented to the other ear, since well-timed inhibition should interact with excitation even if it is entirely of the shunting type. see more In contrast to these predictions, we found that the timing of the input from either Cobimetinib solubility dmso ear is unaffected by the phase of the input from the other ear. Our results therefore suggest that the timing

of the inhibitory input from either ear is not sufficiently precise to allow it to shift the ITD tuning (Joris and Yin, 2007; Zhou et al., 2005). This argument still holds true in the presence of inhibition from both ears. We cannot entirely exclude that the use of anesthetics may have influenced the timing precision of the inhibition. Effects of ketamine/xylazine on subcortical auditory processing are typically mild (Smith and Mills, 1989; Ter-Mikaelian et al., 2007), and both bushy cells (Kuenzel et al., 2011) and primary neurons of the MNTB aminophylline (Hermann et al., 2007; Kopp-Scheinpflug et al., 2008) in gerbil show considerable spontaneous activity even under ketamine/xylazine anesthesia. Decreased inhibition has been reported in the dorsal cochlear nucleus (Navawongse and Voigt, 2009). However, the original evidence favoring well-timed inhibition was also obtained under ketamine/xylazine anesthesia (Brand et al., 2002; Pecka et al., 2008). Another possible confounder is that most of the inhibition is somatic and may have been disrupted when we made recordings. However, somatic inhibitory responses

in the MSO are not disrupted by positive pressures at least ten fold higher than what we used during approach of cells for juxtacellular recordings (Couchman et al., 2012). The presence in the MSO of strong glycinergic inhibitory inputs originating from both the ipsi- (LNTB) and contralateral ear (MNTB) is well established, but its function has been debated (reviewed in Grothe et al., 2010). Because of the linearity of the interaction between both ears, a role of well-timed inhibition in shifting the best ITD (Brand et al., 2002; Pecka et al., 2008) seems unlikely. The low variance at the worst ITD suggests that it is the periodic absence of excitatory input rather than phase-locked inhibition that sets the firing rate during the worst ITD. A possible role for inhibition is that it may improve the dynamic range of the MSO neurons, similar to its proposed role in the nucleus laminaris (Yamada et al.

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