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their ability to hear speech in noise as measured by standard- ized tests, and this advantage increases with extent of musical
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Musicians also excel in tasks that test working memory, and this ability relates to speech-in-noise percep- tion. We reasoned that these performance advantages might manifest themselves in a brainstem that better maintains its synchrony in the presence of background noise. Using stim- ulus-to-response correlations as a metric of brainstem integrity in noise, this was the case. Responses to a speech syllable presented in a quiet background were relatively indistinguishable in normal-hearing adults regardless of their musical backgrounds. However, when the same syllable was masked by multispeaker babble, the musicians’ responses maintained an extraordinary degree of robustness, while the nonmusicians’ responses deteriorated (Fig. 7). Closer exami- nation of the response spectra revealed that harmonics of the fundamental frequency of the syllable were a source of degra- dation in the non-musicians. Larger noise-induced delays in discrete peak timing were noted in non-musicians as well. It may be that enhanced processing of these higher-frequency components of sound facilitates the formation of auditory units and thus sets the stage for the stream segregation required for pulling sounds from noise. Thus, the precision in processing complex sounds in the auditory brainstem may be a precursor to successful SIN perception, and brainstem precision in musi- cians—likely driven by engagement with sound—may under- gird their advantage in listening in noise.
experience.
Linguistic transfer IV: Regularity detection and reading,
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The specific difference, selective enhancements of harmonics two and four in the repet- itive condition, has a relationship with behavior. In school-age children, the extent of these enhancements correlates dramati- cally with reading ability. The sound elements that result in brainstem deficiencies—poor readers in this study and oth- ers88,89,113,125,132—are the same aspects of auditory processing that
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sounds.
Vocal emotion, Strait et al 2009.54 A baby’s cry is a mix of
harmonic and stochastic sounds strung together into an emotion-evoking signal. The acoustical variety packed into this short quarter-second sample makes this one of our most complex stimuli, and the pattern of response differences seen between musicians and non-musicians again speaks to the selective patterns of enhancement—and in this case also response suppression—engendered by musicianship. Zeroing in on the responses to a harmonic, relatively simple (112–142
The ability to track regularities and to respond appropriately to change are hallmarks of the sensory systems. In the human auditory brainstem, we recently demonstrated that responses to a given sound differ depending on whether that sound is presented in a train by itself or embed-
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We speculate that some com- mon mechanisms are at work. One mechanism might be profi- ciency at noise exclusion—the ability to extract relevant signals
Chandrasekaran et al., 2009.
ded in a series of different sounds.
are enhanced in musicians.
Cognitive skills such as auditory memory and attention, enhanced in musicians, invoke corti- cofugal mechanisms that tune brainstem processing. The poor- er engagement of cognitive skills in poor readers fails to solidi- fy the corticofugal tuning of brainstem processing of complex
from a jumble of sounds.
Fig. 6. The voicing contour of this stimulus, “mi,” dipped from about 110 Hz, down to 90 Hz and then back up (thin black lines). The precision with which the brain- stem response phase locked to the stimulus pitch (thick yellow) was superior in
53
musicians. Modified from Wong et al., 2007.
tracking, measured by how closely in frequency the phase
locking in the response matched the changing pitch of the
syllables, and strength of phase locking, measured by auto-
correlation, both were greater in musicians than in nonmu-
sicians. Notably, the musicians’ advantage increased as the
complexity of the tone increased (Fig. 6). The most complex,
dipping, tone best distinguished the groups, while responses
to the level tone differed little between groups. The accuracy
of brainstem pitch-tracking of the dipping tone was correlat-
ed with the length of musical study, indicating that the dif-
ferences between groups are likely due to musicianship
rather than innate subject differences. This subcortical
enhancement in musicians also may provide a mechanism to
explain why musicians show a facility for learning foreign
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Linguistic transfer III: Speech in noise, Parbery-Clark et
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languages.
One of the biggest communication complaints, affecting school children, hearing impaired individuals, older adults, and everyone in between, is difficulty hearing conver- sations in noisy backgrounds. While many populations are affected, musicians, in whom stream segregation and object formation are required for parsing melodies from back- ground harmonies, tend to cope with noisy backgrounds especially well. Musicians, in fact, are dramatically better in
al., 2009.
20 Acoustics Today, July 2010