brain sciences Review Processing of Degraded Speech in Brain Disorders Jessica Jiang 1, Elia Benhamou 1, Sheena Waters 2 , Jeremy C. S. Johnson 1, Anna Volkmer 3, Rimona S. Weil 1 , Charles R. Marshall 1,2, Jason D. Warren 1,† and Chris J. D. Hardy 1,*,† 1 Dementia Research Centre, Department of Neurodegenerative Disease, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK;
[email protected] (J.J.);
[email protected] (E.B.);
[email protected] (J.C.S.J.);
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[email protected] (J.D.W.) 2 Preventive Neurology Unit, Wolfson Institute of Preventive Medicine, Queen Mary University of London, London EC1M 6BQ, UK;
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[email protected]; Tel.: +44-203-448-3676 † These authors contributed equally to this work. Abstract: The speech we hear every day is typically “degraded” by competing sounds and the idiosyncratic vocal characteristics of individual speakers. While the comprehension of “degraded” speech is normally automatic, it depends on dynamic and adaptive processing across distributed neural networks. This presents the brain with an immense computational challenge, making de- graded speech processing vulnerable to a range of brain disorders. Therefore, it is likely to be a sensitive marker of neural circuit dysfunction and an index of retained neural plasticity. Consid- ering experimental methods for studying degraded speech and factors that affect its processing in healthy individuals, we review the evidence for altered degraded speech processing in major Citation: Jiang, J.; Benhamou, E.; neurodegenerative diseases, traumatic brain injury and stroke.