Daniel B. Polley, Ph.D.
Harvard Medical School
Associate Professor of Otology and Laryngology
Amelia Peabody Neural Plasticity Unit
Research Area Affiliations
Early stages of auditory processing feature a variety of biophysical and synaptic specializations that allow neurons to precisely synchronize action potential timing to spectral, temporal and dichotic features within the acoustic source signal. As afferent activity wends its way up the central auditory neuroaxis, the functional organization changes to support more integrative and contextual processing until, at the level of the auditory cortex, the high-fidelity temporal representations from earlier stages have been almost entirely reformatted to rate-based abstractions of the original signal. Although auditory cortex neurons are ill-equipped to encode rapid temporal fluctuations through precise spike timing, they are endowed with a plasticity that supports specific, lasting and adaptive adjustments in rate-based feature tuning. Dr. Polley's laboratory seeks to understand how ‘bottom up’ sensory traces are modulated by cognitive influences such as emotion, learning and prediction in a manner that accentuates perceptual salience and facilitates adaptive behavior. Currently, he pursues this idea in two ways: Firstly, by exploring how neurons in the deep layers of the auditory cortex refine subcortical sound processing through the vast but poorly understood network of corticofugal projections; Secondly, by studying the neural circuits that link sensory traces with behavioral reinforcement signals to enable adaptive plasticity of cortical sound representations.
The lab is deeply interested in exploring therapeutic applications for our research on brain plasticity. Our sense of hearing arises from an electrochemical dialogue between the cochlea and the brain. Dr .Polley is committed to understanding how the brain can further isolate, denoise or otherwise enhance imperfect signals from a damaged cochlea to reinstate this dialogue and allow individuals to function in our noisy society. He studies this in animal models by tracking the intrinsic plasticity mechanisms that allow higher auditory areas to partially restore actionable sound representations after profound cochlear hearing loss. The lab translates these discoveries into non-invasive treatments for humans who struggle with hearing impairment or tinnitus. To date, their clinical research has focused on programming and testing new types of "audio games" designed to diagnose and rehabilitate auditory processing deficits by engaging and directing the brain’s intrinsic capacity for adaptive reorganization.
Immersive audiomotor game play enhances neural and perceptual salience of weak signals in noise. Whitton JP, Hancock KE, Polley DB. Proc Natl Acad Sci U S A. 2014;111(25):2606-15. Download a PDF file.
Online stimulus optimization rapidly reveals multidimensional selectivity in auditory cortical neurons. Chambers AR, Hancock KE, Sen K, Polley DB. The Journal of Neuroscience. 2014;34(27):8963-75. Download a PDF file.
Brief hearing loss disrupts binaural integration during two early critical periods of auditory cortex development. Polley DB, Thompson JH, Guo W. Nature Communications. 2013;4(2547):doi: 10.1038/ncomms3547.
EphA signaling impacts development of topographic connectivity in auditory corticofugal systems. Torii M, Hackett TA, Rakic P, Levitt P, Polley DB. Cerebral Cortex. 2012;23(4):775-785.
Monaural deprivation disrupts development of binaural selectivity in auditory midbrain and cortex. Popescu MV, Polley DB. Neuron. 2010;65(5):718-731.