title: The eye as a window to the listening brain: neural correlates of pupil size as a measure of cognitive listening load.
abstract: An important aspect of hearing is the degree to which listeners have to deploy effort to understand speech. One promising measure of listening effort is task-evoked pupil dilation. Here, we use functional magnetic resonance imaging (fMRI) to identify the neural correlates of pupil dilation during comprehension of degraded spoken sentences in 17 normal-hearing listeners. Subjects listened to sentences degraded in three different ways: the target female speech was masked by fluctuating noise, by speech from a single male speaker, or the target speech was noise-vocoded. The degree of degradation was individually adapted such that 50% or 84% of the sentences were intelligible. Control conditions included clear speech in quiet, and silent trials. The peak pupil dilation was larger for the 50% compared to the 84% intelligibility condition, and largest for speech masked by the single-talker masker, followed by speech masked by fluctuating noise, and smallest for noise-vocoded speech. Activation in the bilateral superior temporal gyrus (STG) showed the same pattern, with most extensive activation for speech masked by the single-talker masker. Larger peak pupil dilation was associated with more activation in the bilateral STG, bilateral ventral and dorsal anterior cingulate cortex and several frontal brain areas. A subset of the temporal region sensitive to pupil dilation was also sensitive to speech intelligibility and degradation type. These results show that pupil dilation during speech perception in challenging conditions reflects both auditory and cognitive processes that are recruited to cope with degraded speech and the need to segregate target speech from interfering sounds.
authors.affiliation: Section Audiology, Dept. of Otolaryngology-Head and Neck Surgery and EMGO Institute for Health and Care Research, VU University Medical Center, De Boelelaan 1118, 1081 HZ, Amsterdam, The Netherlands; Department of Behavioural Sciences and Learning, Linnaeus Centre HEAD, The Swedish Institute for Disability Research, Linköping University, SE-581 83 Linköping, Sweden. Electronic address: aa.zekveld@vumc.nl.
authors.forename: Adriana A
authors.initials: AA
authors.lastname: Zekveld
authors.affiliation: Department of Psychology, VU University, Van der Boechorststraat 1, 1081 BT Amsterdam, The Netherlands.
authors.forename: Dirk J
authors.initials: DJ
authors.lastname: Heslenfeld
authors.affiliation: Department of Behavioural Sciences and Learning, Linnaeus Centre HEAD, The Swedish Institute for Disability Research, Linköping University, SE-581 83 Linköping, Sweden; Department of Psychology, Queen's University, 62 Arch Street, Kingston, Ontario K7L 3N6, Canada; The School of Communication Sciences and Disorders and The Brain and Mind Institute, Natural Sciences Centre, Western University, London, Ontario N6A 5B7, Canada.
authors.forename: Ingrid S
authors.initials: IS
authors.lastname: Johnsrude
authors.affiliation: Section Audiology, Dept. of Otolaryngology-Head and Neck Surgery and EMGO Institute for Health and Care Research, VU University Medical Center, De Boelelaan 1118, 1081 HZ, Amsterdam, The Netherlands.
authors.forename: Niek J
authors.initials: NJ
authors.lastname: Versfeld
authors.affiliation: Section Audiology, Dept. of Otolaryngology-Head and Neck Surgery and EMGO Institute for Health and Care Research, VU University Medical Center, De Boelelaan 1118, 1081 HZ, Amsterdam, The Netherlands.
authors.forename: Sophia E
authors.initials: SE
authors.lastname: Kramer
mesh_terms: D000328:Adult; D053483:Eye Movement Measurements; D005260:Female; D005625:Frontal Lobe / Q000502:physiology*; D059907:Functional Neuroimaging / Q000379:methods*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D011680:Pupil / Q000502:physiology*; D013065:Speech Intelligibility / Q000502:physiology*; D013067:Speech Perception / Q000502:physiology*; D013702:Temporal Lobe / Q000502:physiology*; D055815:Young Adult
keywords: Cognitive processing load; Degraded speech perception; Functional magnetic resonance imaging; Pupillometry