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Auditory Brainstem Response (ABR)

Auditory Brainstem Response (ABR). What is the ABR? The evoked potential from an auditory stimulus measured at the brainstem (inferior colliculus ) Electrodes are placed at vertex ( Cz ), ipsilateral lobe/mastoid (reference), contralateral lobe/mastoid (ground)

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Auditory Brainstem Response (ABR)

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  1. Auditory Brainstem Response (ABR) • What is the ABR? • The evoked potential from an auditory stimulus measured at the brainstem (inferior colliculus) • Electrodes are placed at vertex (Cz), ipsilateral lobe/mastoid (reference), contralateral lobe/mastoid (ground) • Waveform often analyzed with respect to waves I to V

  2. Frequency Following Response (FFR) • cABRs: ABR to complex stimuli (e.g., speech, music, etc...) /da/ Skoe & Kraus 2010 Ear and Hearing

  3. Temporal Fine Structure (TFS) and Reverb Sayles & Winter 2008 Neuron http://research.meei.harvard.edu/chimera/index.html

  4. Experiment • Subjects: 22 (ages 21 – 55) • Spatial Attention Task • Simulated room acoustics (anechoic, intermediate reverb, high reverb) • Report 4 digits stream from front (0 ITD), in the presence of same-voice digits from +15 and -15 degrees • Cues: TFS (<1000Hz) and Envelope (>1000Hz) • Brainstem Measurement • FFRs: /da/ stimulus (F0 = 100Hz), both positive and negative polarity • Phase locking value analysis (orthogonal): FFRenv and FFRcar

  5. Results: Spatial Attention Task re Age

  6. FFR components • The envelope component dominates FFR at F0, and carrier dominates above F0

  7. Age, FFR and selective attention • FFRenv-100 was a better predictor of selective attention performance for young adults, whereas FFRcar-avg was for older adults. • Weak envelope coding did not explain age effects • Nor did high-frequency thresholds

  8. Implications • Reduced overall FFR in older adults has not always correlated with poorer perceptual abilities than younger adults. • FFRenv-100 component was found to decline at an earlier age than associated with age-related hearing loss, and could be a possible indicator of hearing threshold changes. • Reverberation affects carrier ITDs (TFS) more so than envelope ITDs • Due to poor envelope coding in older listeners, reliance on TFS info is more susceptible to everyday reverberant settings. • Younger adults have less susceptibility to effects of reverberation due to a more robust encoding of envelope info.

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