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Research Projects

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Neural mechanisms and plasticity underlying auditory categorization and learning

Using novel multivariate classification techniques to "decode" electrical brain responses (EEG), we are examining how the human brain groups sounds and learns to categorize auditory events--the process of categorical  perception (CP). We have shown neural correlates of phonetic properties of speech emerge as early as primary auditory cortex (~150 ms after sound onset) in both evoked and induced oscillatory modes of brain activity. This is much earlier and lower in the auditory system than previously thought. We find that speech becomes categorically organized at the neural level as early as primary auditory cortex (PAC) under some circumstances (e.g., highly-experienced listeners).  We have also shown that categories are dynamically shaped by experience, goal-directed attention, and stimulus context (e.g., familiarity).

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Selected publications:

Bidelman, G. M. & Walker, B. (2017). Attentional modulation and domain specificity underlying the neural organization of auditory categorical perception. European Journal of Neuroscience, 45, 690-699.

Bidelman, G. M., Lee, C.-C. (2015). Effects of language experience and stimulus context on the neural organization and categorical perception of speech. NeuroImage, 120, 191-200.

Bidelman, G. M., & Alain, C. (2015). Musical training orchestrates coordinated neuroplasticity in auditory brainstem and cortex to counteract age-related declines in categorical vowel perception. Journal of Neuroscience, 35(2), 1240 –1249.

Bidelman, G. M. (2015). Induced neural beta oscillations predict categorical speech perception abilities. Brain and Language, 141, 62-69.

Bidelman, G. M., Moreno, S., Alain, C. (2013). Tracing the emergence of categorical speech perception in the human auditory system. NeuroImage, 79, 201-212.

Cognitive aging and neuroplasticity across the lifespan

A translational avenue of our research investigates cognitive aging and changes in speech-language function that occur across the lifespan. Our aging studies have revealed that normal age, mild cognitive impairment, and age-related hearing loss impair the functional coupling between brainstem and cortex during speech processing, resulting in more redundancy in the brain's representations for speech across different levels of the neuroaxis. This body of work emphasizes that declines in listening skills later in life depend not only on the quality of signal representations within individual brain areas per se, but rather, how information is transmitted between regions of the speech network. Promisingly, our plasticity studies suggest that auditory experiences like musical training might help counteract age-related declines in speech processing. Our findings underscore the fact that robust neuroplasticity is not restricted by age and may serve to strengthen speech listening skills that decline across the lifespan.

Selected publications:

Bidelman, G. M., Lowther, J. E., Tak, S. H., & Alain, C. (2017). Mild cognitive impairment is characterized by deficient hierarchical speech coding between auditory brainstem and cortex. Journal of Neuroscience, 37(13), 3610-3620.

Khatun, S., Morshed, B. I., & Bidelman, G. M. (2017). Single channel time-frequency features to detect mild cognitive impairment. Proceedings of the IEEE International Symposium on Medical Measurement and Applications (IEEE MeMeA 2017), Rochester, MN.

Bidelman, G. M., & Alain, C. (2015). Musical training orchestrates coordinated neuroplasticity in auditory brainstem and cortex to counteract age-related declines in categorical vowel perception. Journal of Neuroscience, 35(2), 1240 –1249. 

Bidelman, G.M., Villafuerte, J.W., Moreno, S., Alain, C. (2014). Age-related changes in the subcortical-cortical encoding and categorical perception of speech. Neurobiolology of Aging 35, 2526-40.

Neural mechanisms underlying auditory scene analysis

We are investigating the subcortical and cortical mechanisms which guide auditory scene analysis and cocktail party listening. Of interest to the lab is characterizing the neural basis of individual differences in speech-in-noise perception and how SIN listening skills are affected by disorders/impairments (e.g.,hearing loss) and lifelong experiences (e.g., bilingualism, musical training)

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Distributed source analysis of clean vs. degraded speech coding

Selected publications:

Bidelman, G. M. & Howell, M. (2016). Functional changes in inter- and intra-hemispheric auditory cortical processing underlying degraded speech perception. NeuroImage, 124, 581-590. 

Bidelman, G. M. & Patro, C. (2016). Auditory perceptual restoration and illusory continuity correlates in the human brainstem. Brain Research, 1646, 84-90. 

Bidelman, G. M. (2016). Relative contribution of envelope and fine structure to the subcortical encoding of noise-degraded speech. Journal of the Acoustical Society of America, 140(4), EL358-363. 

Bidelman, G. M., & Bhagat, S. P. (2015). Right ear advantage drives the link between olivocochlear efferent "antimasking" and speech-in-noise listening benefits. NeuroReport, 26, 483-487.

Bidelman, G. M., & Dexter, L. (2015). Bilinguals at the "cocktail party": Dissociable neural activity in auditory-linguistic brain regions reveals neurobiological basis for nonnative listeners' speech-in-noise recognition deficits. Brain and Language, 143, 32-41.

Functional characterizations of the human frequency-following response (FFR)

We specialize in the recording of the FFR, a sustained phase-locked potential that offer a "neural fingerprint" of sound encoding within the EEG. This neurophonic offers a high-fidelity representation of the speech signal. In fact, listeners can identify speech from these neural responses when they are replayed as auditory stimuli. FFRs are becoming a mainstream tool for understanding the neural encoding of speech, music, and experience-dependent plasticity in auditory processing. Despite potential clinical and empirical utility, FFRs are not widely used. In a series of studies, we are providing comprehensive characterizations of the FFR including its source generators and distinctions from the conventional auditory brainstem response used clinically. The lab has also developed new objective statistics for detecting FFRs as well as optimal stimulus paradigms for eliciting the responses when simultaneously recorded with cortical potentials. The goal of this work is to make this particular auditory evoked potential more available to researchers and clinicians and provide a better understanding of its physiological basis, response characteristics, and relation to other common electrophysiological measures

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Selected publications:

Bidelman, G. M. (2018). Sonification of scalp-recorded frequency-following responses (FFRs) offers improved response detection over conventional statistical metrics. Journal of Neuroscience Methods, 293, 59-66.

Weiss, M. W., & Bidelman, G. M. (2015). Listening to the brainstem: Musicianship enhances intelligibility of subcortical representations for speech. Journal of Neuroscience, 35(4), 1687-1691.

Bidelman, G. M. (2015). Multichannel recordings of the human brainstem frequency-following response: Scalp topography, source generators, and distinctions from the transient ABR. Hearing Research, 323, 68-80. 

Bidelman, G. M. (2015). Towards an optimal paradigm for simultaneously recording cortical and brainstem auditory evoked potentials. Journal of Neuro. Methods, 241, 94–100.

How does auditory experience change the hearing brain?

We are investigating how experience and certain forms of training change the brain. Musicians are an exceptional model for studying auditory plasticity given their intense, long-term experience manipulating complex sound information. Our neuroimaging studies demonstrate experience-dependent tuning of the human auditory system with music engagement. Remarkably, musicians' enhancements in brain function are not restricted to music processing; our studies also reveal important benefits to speech and language functions as well as general , non-auditory cognitive abilities (e.g., aspects of memory). We are exploring how music instruction and other forms of experience (e.g., bilingualism) could be used to strengthen speech/language skills and general cognitive abilities across the lifespan.

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Selected publications

Bidelman, G. M., Nelms, C., & Bhagat, S. P. (2016). Musical experience sharpens human cochlear tuning. Hearing Research, 335, 40-46. (PDF)

Bidelman, G. M., Schug, J. M., Jennings, S. G., & Bhagat, S. P. (2014). Psychophysical auditory filter estimates reveal sharper cochlear tuning in musicians. Journal of the Acoustical Society of America, 136(1), EL33-39.

Bidelman, G. M., Krishnan, A., & Gandour, J. T. (2011). Enhanced brainstem encoding predicts musicians' perceptual advantages with pitch. European Journal of Neuroscience, 33(3), 530-538.

Bidelman, G. M., & Krishnan, A. (2010). Effects of reverberation on brainstem representation of speech in musicians and non-musicians. Brain Research, 1355, 112-125.

Cross-domain transfer effects between music and language experience

Recent neuroimaging studies suggest that some aspects of music and language are processed by shared brain regions. This overlap suggests the intriguing possibility that experience in one domain (e.g., music training) might transfer to benefit processing in the other domain (e.g., speech). Neurocognitive models suggest the reverse might also be true, i.e., intense language experience improving music listening skills. In both ERP and behavioral studies we are investigating how music and language experience (particularly tone languages) improve the neural processing of music and language signals. Our findings suggest that under some circumstances, transfer from these experiences to the other can be bidirectional (M->L and L->M).

Cross Domain

Selected publications:

Bidelman, G. M., Hutka, S., & Moreno, S. (2013). Tone language speakers and musicians share enhanced perceptual and cognitive abilities for musical pitch: Evidence for bidirectionality between the domains of language and music. PloS One, 8(4), e60676.

Bidelman, G. M., Gandour, J. T., & Krishnan, A. (2011). Cross-domain effects of music and language experience on the representation of pitch in the human auditory brainstem. Journal of Cognitive Neuroscience, 23(2), 425-434.

Bidelman, G. M., Gandour, J. T., & Krishnan, A. (2011). Musicians and tone-language speakers share enhanced brainstem encoding but not perceptual benefits for musical pitch. Brain and Cognition, 77(1), 1-10.

Is there a neural origin for music?

Why do certain musical pitch relationships sound more pleasant than others? Why have composers adopted the scales and tuning systems they have? The origins of musical consonance have long been debated since the time of Pythagoras. In as series of studies, we are investigating the neural basis of consonance and musical pitch hierarchy. We have found robust correlates of listener's behavioral preferences for musical chords and intervals in the brainstem and as low as the auditory nerve (AN). These findings suggest that certain perceptual attributes of musical pitch are present in the earliest (and pre-attentive) stages of neurophysiological processing.

Consonance

 

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Selected publications:

Bidelman, G. M., Grall, J.(2014). Functional organization for musical consonance and tonal pitch hierarchy in human auditory cortex. NeuroImage, 101, 204-214.

Bidelman, G. M. (2013). The role of the auditory brainstem in processing musically-relevant pitch. Frontiers in Psychology, 4(264), 1-13.

Bidelman, G. M., & Heinz, M. G. (2011). Auditory-nerve responses predict pitch attributes related to musical consonance-dissonance for normal and impaired hearing. Journal of the Acoustical Society of America, 130(3), 1488-1502.

Bidelman, G. M., & Krishnan, A. (2009). Neural correlates of consonance, dissonance, and the hierarchy of musical pitch in the human brainstem. Journal of Neuroscience, 29(42), 13165-13171.