Abstract
Current models successfully describe the auditory cortical response to natural sounds with a set of spectro-temporal features. However, these models have hardly been linked to the ill-understood neurobiological changes that occur in the aging auditory cortex. Modelling the hemodynamic response to a rich natural sound mixture in N = 64 listeners of varying age, we here show that in older listeners' auditory cortex, the key feature of temporal rate is represented with a markedly broader tuning. This loss of temporal selectivity is most prominent in primary auditory cortex and planum temporale, with no such changes in adjacent auditory or other brain areas. Amongst older listeners, we observe a direct relationship between chronological age and temporal-rate tuning, unconfounded by auditory acuity or model goodness of fit. In line with senescent neural dedifferentiation more generally, our results highlight decreased selectivity to temporal information as a hallmark of the aging auditory cortex.
Highlights
Age-related hearing loss is a frequent cause for a decline in speech comprehension, in complex acoustic environments
The largescale topographic organization of acoustic features appears preserved in the auditory cortex of older compared to younger listeners, age-related differences in the marginal profiles of multi-voxel modulation transfer function (MTF) were evident
Tuning to slow temporal rates which abounds in natural sounds and especially in Neuroscience speech (Erb et al, 2019a) was markedly sharper in young compared to older participants
Summary
Age-related hearing loss is a frequent cause for a decline in speech comprehension, in complex acoustic environments. Age-related deficits have been observed in different temporal psychoacoustic tasks (e.g. gap detection; Snell et al, 2002). Those psychoacoustic studies suggest that the precision of processing of temporal cues declines with age In the aged macaque auditory cortex, neurons become more broadly tuned to temporal modulations and temporal fidelity of cortical responses decreases (Ng and Recanzone, 2018). In aged neurons, a shift in neural coding strategy from less temporal coding towards more rate coding of temporal modulations was evident (Overton and Recanzone, 2016; for a review of both coding strategies see Joris et al, 2004). For those neurons that still adhered to a temporal coding strategy, the temporal fidelity decreased, the absolute number of neurons responsive to temporal modulations was unaffected by age (Overton and Recanzone, 2016)
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