Background/study context: Vigilance refers to the ability to sustain and adapt attentional focus in response to changing task demands. For older adults with hearing loss, vigilant listening may be particularly effortful and variable across individuals. This study examined the extent to which neural responses to sudden, unexpected changes in task structure (e.g., from rest to word recognition epochs) were related to pupillometry measures of listening effort.
Methods: Individual differences in the task-evoked pupil response during word recognition were used to predict functional magnetic resonance imaging (MRI) estimates of neural responses to salient transitions between quiet rest, noisy rest, and word recognition in unintelligible, fluctuating background noise. Participants included 29 older adults (M = 70.2 years old) with hearing loss (pure tone average across all frequencies = 36.1 dB HL [hearing level], SD = 6.7).
Results: Individuals with a greater average pupil response exhibited a more vigilant pattern of responding on a standardized continuous performance test (response time variability across varying interstimulus intervals r(27) = .38, p = .04). Across participants there was widespread engagement of attention- and sensory-related cortices in response to transitions between blocks of rest and word recognition conditions. Individuals who exhibited larger task-evoked pupil dilation also showed even greater activity in the right primary auditory cortex in response to changes in task structure.
Conclusion: Pupillometric estimates of word recognition effort predicted variation in activity within cortical regions that were responsive to salient changes in the environment for older adults with hearing loss. The results of the current study suggest that vigilant attention is increased amongst older adults who exert greater listening effort.