ABSTRACT
Normal aging is associated with difficulty understanding speech in adverse listening conditions. A large literature
demonstrates that pure tone hearing thresholds alone do not provide an adequate profile of an individual’s
speech perception in noise (SPIN) abilities, and even individuals with normal sensitivity tend to complain of
speech perception difficulties. Studies of SPIN in aging often compare older adults against younger adults. In
contrast, fewer studies investigate SPIN difficulties in middle-aged adults, leaving a large gap in our knowledge
of SPIN mechanisms in aging. In older adults, pervasive changes throughout the nervous system, including
subcortical temporal processing, cognitive effort, and compensatory frontal activity are related to reduced SPIN
performance. The overall goal of this proposal is to investigate the neural mechanisms of SPIN in younger and
middle-aged adults with normal hearing sensitivity using a multimodal neuroimaging and computational cognitive
neuroscience approach. To achieve this overall goal, this proposal is composed of two study aims: 1) examine
the extent to which temporal processing and cognitive effort during SPIN are affected by middle-age, and 2)
quantify compensatory neural recruitment during SPIN. In service of the first aim, we will compare temporal
processing abilities and cognitive effort during SPIN in younger and middle-aged adults with and without self-
reported SPIN difficulties. In service of the second aim, we will investigate the presence of frontal motor cortex
recruitment during SPIN among the same individuals from the first aim using functional magnetic resonance
imaging and simultaneous pupillometry to assess cognitive effort. Upon completion of the project outlined in this
proposal, we will gain a better understanding of neural mechanisms associated with SPIN in aging, SPIN abilities
in middle-age, and mechanisms driving SPIN difficulties in individuals with normal hearing sensitivity. The
findings from this study also have the potential to inform whether individuals may be responsive to auditory or
cognitive rehabilitation to mitigate SPIN difficulties.