the cochlea: ossicle removal does not change hair cell counts on the basilar membrane, and bone conduction thresholds are reported to be normal [76]. At the same time, it remains possible that unintended outer hair cell damage could have affected the encoding of variations in sound amplitude via reduction of cochlear compressive non-linearities [27]. However, the overall hearing sensitivity of CHL animals was not correlated with their sAM detection thresholds, as measured by either ABRs or behavioral hearing thresholds (Fig. 2). Finally, developmental CHL affects EPSP amplitudes and short-term synaptic depression in pyramidal neurons, and prevents the maturation of inhibitory interneurons [10,12,14], suggesting that changes to the cortical network could contribute to the reduced firing rate and poorer sAM envelope encoding. The reduced overall firing rates in CHL animals may be attributable to a reduction in sound-evoked drive via greater short-term depression of thalamic excitatory afferents to the ACx [10] and/or lemniscal excitatory afferents to the IC [77]. It appears that the loss of inhibitory strength, both at the level of the IC and ACx [58,78] is not sufficient to restore a normal discharge rate, at least for AM stimuli. Perceptual Processing with Hearing Loss: Sensory Versus Non-sensory Factors Our interpretation of the results is that developmental hearing loss leads to a sensory processing deficit that can explain poorer performance on perceptual tasks. However, the results do not address alternative interpretations that involve non-sensory factors. For example, hearing-impaired listeners expend extra listening effort to achieve speech comprehension equivalent to that References 1. Kiorpes L (2006) Visual processing in amblyopia: animal studies. Strabismus 14: 3–10. 2. 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PLoS ONE | www.plosone.org 12 July 2012 | Volume 7 | Issue 7 | e41514