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THE NEUROSCIENCES AND MUSIC II I: DISORDERS AND PLASTICITY
Musical Experience Promotes SubcorticalEfficiency in Processing
Emotional
Vocal SoundsDana L. Strait,a,b Nina Kraus,b,c,d,e Erika
Skoe,b,c
and Richard Ashleya,f
aBienen School of Music, bAuditory Neuroscience Laboratory,
Departments ofcCommunication Sciences, dNeurobiology and
Physiology, eOtolaryngology, and
f Cognitive Science at Northwestern University, Evanston,
Illinois, USA
Tounderstandhowmusical experience influences subcortical
processing of emotionallysalient sounds, we recorded brain stem
potentials to affective vocal sounds. Our resultssuggest that
auditory expertise engenders subcortical auditory processing
efficiencythat is intricately connected with acoustic features
important for the communicationof emotion. This establishes a
subcortical role in the auditory processing of emotionalcues,
providing the first biological evidence for musicians enhanced
perception of vo-cally expressed emotion.
Key words: auditory brain stem response; brain; emotion;
musicians; plasticity
Perception of emotion in speech and musicrelies on shared
acoustic and neural mech-anisms,1 suggesting that extensive
experiencein one domain may lend perceptual benefitsto the other.
Accordingly, musical experienceenhances perceptual sensitivity to
emotion inspeech.2,3
Musical experience also shapes subcorticalsound transcription
(see the paper by Krauset al. in this volume4). Because of its
fidelityin representing spectral and temporal acous-tic features,
the auditory brainstem response(ABR) provides a mechanism for
exploringmusicians subcortical sensitivity to acousticfeatures
contributing to the perception of emo-tion.5 ABRs may also advance
our understand-ing of subcortical function in the processing
ofemotionally charged auditory cues.
To better understand musical experiencesinfluence on neural
processing of affective
Address for correspondence: Dana L. Strait, Auditory
NeuroscienceLaboratory, Northwestern University, 2240 Campus Drive,
Evanston, IL60208. Voice: 847-491-2465.
[email protected]
bFor more information about the Auditory Neuroscience
Labora-tory and the work presented herein, please visit
http://www.brainvolts.northwestern.edu.
speech-related events, we recorded ABRs to anemotionally charged
vocal soundan infantsunhappy cry. We aimed to provide a biologi-cal
basis for musicians enhanced perception ofemotion in speech by
investigating the contri-bution of subcortical mechanisms to
processingvocally communicated emotion.
Methods
Subjects were 30 normal-hearing adultsaged 1935 years, with
musicians grouped ac-cording to two criteria: Musicians by OnsetAge
(MusAge, n = 11, began musical train-ing 7 yr) and Musicians by
Years (MusYrs,n = 15, 10 years of consistent musical
train-ing).Nonmusicians (NonMus)were categorizedby failure to meet
those criteria.
ABRswere elicited by a complex vocal soundderived from an
emotional auditory scene fromthe Center for the Study of Emotions
and At-tention (University of Florida, Gainesville; file278).6 For
further recording and data process-ing parameters see Strait et
al.7
The Neurosciences and Music III: Disorders and Plasticity: Ann.
N.Y. Acad. Sci. 1169: 209213 (2009).doi:
10.1111/j.1749-6632.2009.04864.x c 2009 New York Academy of
Sciences.
209
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210 Annals of the New York Academy of Sciences
Figure 1. Stimulus and grand average response waveforms. The
boxes correspond tothe periodic and complex portions, respectively.
Figures adapted from Strait et al.7 withpermission. (In color in
Annals online.)
We divided the stimulus into two segments(periodic and complex)
that were acousti-cally contrastive and internally consistent.
Neu-ral responses to the complex region resulted ina series of
peaks that aligned with amplitudebursts in the stimulus (Fig. 1).
Peak latencies andamplitudes were recorded for the largest andmost
replicable peaks, whereas rectified meanamplitudes (RMAs) provided
a gross measureof response amplitude.
We extracted spectral components of theneural responses using
the fast Fourier trans-form. Amplitudes were recorded for
spectralpeaks corresponding to the stimuluss funda-mental frequency
and spectral componentsrepresenting the maxima within given
fre-quency ranges (F0: 280305; H2: 470485; H3:570585Hz),
interpreted to correspond to rep-resentations of pitch (F0) and
timbre (H2, H3).
Results
Regression analyses supported the groupingof musicians into two
subgroups: whereas theMusYrs grouping was predicted best by
ampli-tude and latencymeasures (P < 0.001;MusAgeP < 0.06),
MusAge was predicted best by fre-quency encoding measures (P <
0.05; MusYrsP < 0.40).
Both MusYrs and MusAge musicians re-sponses exhibited
enhancements and econ-
omy connected with time-varying acousticfeatures of the
stimulus. Enhancements (largertime- and frequency-domain response
magni-tudes) were apparent in musicians responsesto the complex
portion of the sound, witheconomy (smaller amplitudes) seen in
their re-sponses to the periodic portion.
Figure 1 shows both the stimulus and aver-age responses for
MusYrs and NonMus, withboxes defining acoustically distinct
sections.The first portion of the stimulus is character-ized by
greater periodicity, whereas the secondis characterized by greater
complexity (devia-tion in pitch from the F0: 0.5% in the
periodicportion and 2.7% in the complex, harmonicjitter: 1.27% and
2.03%, and signal-to-noiseratio: 13.46 and 6.82 dB).
The response RMAs are plotted inFigure 2A, for which an ANOVA
revealed aninteraction between group and response por-tion (F =
6.04, P < 0.02). This indicatesthat MusYrs and NonMus have
differentiatedresponses to the two sections. Whereas theMusYrs
within-group RMAs differ betweenthe periodic and complex portions
(t = 4.70,P < 0.0001), NonMus do not (t = 0.025,P < 0.99).
Peak amplitudes confirmMusYrs tohave larger responses to the
complex portionthan NonMus (peak 1: F = 10.25, P < 0.003;peak 2:
F = 4.88, P < 0.03).
Peak amplitudes within the complex por-tion correlated with
years of musical practice
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Strait et al.: Musical Experience and Neural Efficiency 211
Figure 2. Interactions between responses to theperiodic and
complex stimulus portions. (A) Group portion interaction between
MusYrs and NonMusresponse RMAs and (B) MusAge and NonMus F0.(C)
MusAge also show enhanced encoding of fre-quencies above the F0 in
responses to the complexportion. (In color in Annals online.)
across all individuals with musical experience(n = 20; Fig. 3;
peak 1: r = 0.454, P < 0.04).Timing-related enhancements were
specificallyobserved in MusYrs responses, even as early asthe onset
(Fig. 4; onset peak:F = 4.82,P < 0.04;peak 1: F = 8.72, P <
0.006). Earlier latenciesin musicians reflect faster synchronous
neuralresponses to the timing characteristics of thestimulus.
Compared to NonMus, MusAge showed en-hanced representations of
frequencies impor-tant for the perception of pitch and timbre in
re-sponses to the complex stimulus portion. These
differences were connected with acoustic char-acteristics of the
auditory input. AnANOVAre-vealed an interaction between group and
F0 en-coding for the two response portions (F = 7.04,P < 0.01),
indicating that MusAge and Non-Mus have differentiated F0 responses
to the twosections. MusAge showed smaller representa-tions of the
F0 in responses to the periodic por-tion of the stimulus
thanNonMus, but larger F0amplitudes to the complex portion (Fig.
2B; pe-riodic: F = 7.04, P < 0.01; complex: F = 5.04,P <
0.03). F0 amplitudes in responses to thecomplex portion correlated
with the age thatmusical training began, with individuals whobegan
at an earlier age showing larger F0 rep-resentations (Fig. 3: r =
0.500, P < 0.03).MusAge also demonstrated enhanced
repre-sentations of spectral peaks H2 and H3 in re-sponses to the
complex portion of the stim-ulus compared with NonMus (Fig. 2C;
H2:F = 7.95, P < 0.01; H3: F = 6.16, P < 0.02).
Conclusions
We suggest that musical experience has per-vasive effects on the
auditory system, resultingin fine neural tuning to acoustic
features im-portant for vocal communication. Musical ex-perience
sharpens subcortical auditory process-ing, with the behavioral
relevance and relativecomplexity of the stimulus playing a
prominentrole in subcortical malleability. This sharpen-ing is
likely mediated by the corticofugal sys-tem known to shape
receptive field propertiesin the primary auditory cortex, thalamus,
andauditory brain stem.8
The interplay between response enhance-ment and economy may
engender musiciansenhanced perceptual capabilities of emotionalcues
in speech.2,3 Musicians responses to theperiodic stimulus section
demonstrate smallermagnitudes, reflecting neural efficiency
(re-cruitment of fewer resources) in processing sim-pler acoustic
features. Such observations havebeen interpreted to reflect
domain-general ex-pertise.9 MusYrs faster responses indicate
that
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212 Annals of the New York Academy of Sciences
Figure 3. Correlations between musical experience and
subcortical responsecharacteristics.
Figure 4. Peak latencies for MusYrs and NonMus. (In color in
Annals online.)
long-term musical experience contributes toenhanced subcortical
timing.
Musics spectral and temporal complexitymakes it a powerful tool
for engendering neuralplasticity during optimal periods of auditory
de-velopment.Our data suggest thatmusical train-ing prior to the
age of seven has an impact onsubcortical frequency representation,
whereastiming-related enhancements are affected byduration of
practice. This indicates an optimalperiod for the development of
pitch and timbreencoding strategies. Deprivation studies pro-vide
evidence for optimal periods in the acquisi-tion of tonotopic maps
in the primary auditorycortex, with exposure to spectrally and
tem-porally complex auditory input necessary forauditory
evoked-response development.10,11
There does not seem to be a similar optimalperiod for the
development of neural repre-sentations of timing. The discrepancy
betweentiming- and frequency-related effects aligns
with evidence of distinct subcortical encodingmechanisms for
different features of acousticstimuli.9,12
Fast subcortical-limbic pathways for emo-tional processing are
established in the visualsystem,13 with analogous pathways in the
au-ditory system indicated more recently.1416 Byshowing subcortical
involvement in the encod-ing of acoustic features foundational to
thevocal communication of emotion, our resultsprovide an advance in
the study of human per-ception of biological states.
In conclusion, we found that musical train-ing engenders
subcortical efficiency that isconnected with acoustic features
integral tothe communication of emotion. Thus weprovide biological
evidence for musiciansperceptual enhancements in detecting vo-cally
expressed emotion and reveal profoundinteraction between cognitive
and sensoryprocesses.4,9,1618
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Strait et al.: Musical Experience and Neural Efficiency 213
Acknowledgements
This work was funded in part by NSF Grant0544846 and a Graduate
Research Grant fromNorthwestern University. The authors wouldlike
to thank Jennifer Krizman for assistance inpreparing final figures
for this manuscript.
Conflicts of Interest
The authors declare no conflicts of interest.
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