Normal hearing is not enough to guarantee robust encoding of suprathreshold features important in everyday communication

Abstract

"Normal hearing" is typically defined by threshold audibility, even though everyday communication relies on extracting key features of easily audible sound, not on sound detection. Anecdotally, many normal-hearing listeners report difficulty communicating in settings where there are competing sound sources, but the reasons for such difficulties are debated: Do these difficulties originate from deficits in cognitive processing, or differences in peripheral, sensory encoding? Here we show that listeners with clinically normal thresholds exhibit very large individual differences on a task requiring them to focus spatial selective auditory attention to understand one speech stream when there are similar, competing speech streams coming from other directions. These individual differences in selective auditory attention ability are unrelated to age, reading span (a measure of cognitive function), and minor differences in absolute hearing threshold; however, selective attention ability correlates with the ability to detect simple frequency modulation in a clearly audible tone. Importantly, we also find that selective attention performance correlates with physiological measures of how well the periodic, temporal structure of sounds above the threshold of audibility are encoded in early, subcortical portions of the auditory pathway. These results suggest that the fidelity of early sensory encoding of the temporal structure in suprathreshold sounds influences the ability to communicate in challenging settings. Tests like these may help tease apart how peripheral and central deficits contribute to communication impairments, ultimately leading to new approaches to combat the social isolation that often ensues.auditory processing disorder | frequency following response | individual differences | auditory scene analysis | informational masking M aking sense of conversations in busy restaurants or streets is a challenge, as competing sound sources add up to create a confusing cacophony. Central to communicating in such environments is selective attention, the process that enables listeners to filter out unwanted events and focus on a desired source (1). By listening for an object with a particular attribute (for instance, by focusing on the source from straight ahead), competing sound sources can be suppressed and the desired object brought into a listener's attentional focus (2-4).Many listeners with clinically normal hearing complain of difficulties with selective auditory attention (5). Because such difficulties manifest in complex everyday tasks, they are often assumed to arise from central processing deficits (6, 7). However, there is no real consensus: Are "normal-hearing" listeners who have trouble conversing in ordinary social settings suffering from a central deficit, or is there a peripheral cause (8, 9)? Reflecting this ongoing debate, clinical diagnoses use a range of labels to describe normal-hearing listeners who cannot communicate easily when there are competing sound sources; there is no standard procedure for ...

A Little Goes a Long Way: How the Adult Brain Is Shaped by Musical Training in Childhood

“…Our findings are consistent with reports that adult nonhuman animals receive residual behavioral benefits from brief auditory training that they received as juveniles (Sarro and Sanes, 2011), that regular physical activity early in life is associated with better cognitive function later in life in humans (Dik et al, 2003) and nonhumans (Gomes da Silva et al, 2012), and that past musical experience is predictive of enhanced cognitive performance in older adults (Hanna-Pladdy and MacKay, 2011). Although the present study did not investigate the enduring behavioral benefits of childhood music training, we draw from prior work linking enhanced auditory brainstem encoding with heightened auditory perception, executive function, and auditory-based communication skills (Parbery-Clark et al, 2009;Ruggles et al, 2011;Kraus et al, 2012;Krizman et al, 2012;Song et al, 2012) to suggest that musical training during development may produce long-lasting positive effects on the adult brain. During development, negative alterations in the environment, such as noise or limited acoustic diversity, lead to longlasting neural despecializations, including reduced neural synchrony and decreased frequency selectivity (Zhang et al, 2002;Chang and Merzenich, 2003;Ruggles et al, 2011).…”

Age-Related Changes in the Relationship Between Auditory Brainstem Responses and Envelope-Following Responses

“…Elderly listeners with normal hearing thresholds still have deficits in complex temporal processing tasks (Dubno et al 1984;Schneider et al 1994;Snell and Frisina 2000;Mazelova et al 2002;Ruggles et al 2011). Among listeners with matched thresholds, the actual amplitudes of the ABR waves are significantly lower with age (Boettcher et al 1993;Konrad-Martin et al 2012).…”

Interindividual Variation of Sensitivity to Frequency Modulation: Its Relation with Click-Evoked and Distortion Product Otoacoustic Emissions

“…Given this assumption, the low-rate FM detection limen (FMDL) has been used to assess the ability to use phase locking information (Strelcyk and Dau 2009;Ruggles et al 2011;Grose and Mamo 2012).…”