Music and speech are very cognitively demanding auditory phenomena generally attributed to cortical rather than subcortical circuitry. We examined brainstem encoding of linguistic pitch and found that musicians show more robust and faithful encoding compared with nonmusicians. These results not only implicate a common subcortical manifestation for two presumed cortical functions, but also a possible reciprocity of corticofugal speech and music tuning, providing neurophysiological explanations for musicians' higher language-learning ability.Both music and spoken language involve the use of functionally and acoustically complex sound and are generally attributed to the neocortex [1][2][3][4] . Less is known about how long-term experience using these complex sounds shapes subcortical circuitry and the context specificity and reciprocity of this tuning 5 . By measuring the frequency following response (FFR), which presumably originates from the auditory brainstem (inferior colliculus) and encodes the energy of the stimulus fundamental frequency (f 0 ) with high fidelity 6 , previous work 7 has found increased linguistic pitch pattern encoding in Mandarin-speaking subjects relative to English-speaking subjects. These results reflect Mandarin-speaking subjects' long-term exposure to linguistic pitch patterns, as Mandarin Chinese, a tone language, uses pitch to signal word meaning (for example, /ma/ spoken with high or rising pitch patterns means 'mother' or 'numb', respectively). Moreover, similar to research on short-term perceptual learning 8 , these results can be viewed as context specific (that is, linguistic experiences, subserved by the cortex, enhance the encoding of linguistic information at the Correspondence should be addressed to P.C.M.W. (pwong@northwestern.edu). 5 These authors contributed equally to this work.Note: Supplementary information is available on the Nature Neuroscience website. COMPETING INTERESTS STATEMENTThe authors declare no competing financial interests. Author Manuscript brainstem). The nonspecificity of this long-term usage effect, though largely unknown, is both theoretically interesting and clinically and educationally relevant. Nonspecificity would suggest that either speech-or music-related experience can tune sensory encoding in the auditory brainstem via the corticofugal pathway. Notably, this tuning, whether speech-or music-induced, would enhance all relevant auditory functions (both speech and music) subserved by the rostral brainstem. HHS Public AccessWe measured FFR responses to linguistic pitch patterns at the rostral brainstem in ten amateur musicians and ten nonmusicians who had no previous exposure to a tone language (see Supplementary Table 1 online). Musicians (instrumentalists) had at least 6 years of continuous musical training (mean = 10.7 years) starting at or before the age of 12.Nonmusicians had nomore than3 years (mean = 1.2 years) at any time in their life. Informed written consent was obtained from all subjects. While watching a video, subjects listened...

The current study investigates the learning of nonnative suprasegmental patterns for word identification. Native English-speaking adults learned to use suprasegmentals (pitch patterns) to identify a vocabulary of six English pseudosyllables superimposed with three pitch patterns (18 words). Successful learning of the vocabulary necessarily entailed learning to use pitch patterns in words. Two major facets of sound-to-word learning were investigated: could native speakers of a nontone language learn the use of pitch patterns for lexical identification, and what effect did more basic auditory ability have on learning success. We found that all subjects improved to a certain degree, although large individual differences were observed. Learning success was found to be associated with the learners' ability to perceive pitch patterns in a nonlexical context and their previous musical experience. These results suggest the importance of a phonetic-phonological-lexical continuity in adult nonnative word learning, including phonological awareness and general auditory ability.

Studies evaluating phonological contrast learning typically investigate either the predictiveness of specific pretraining aptitude measures or the efficacy of different instructional paradigms. However, little research considers how these factors interact-whether different students learn better from different types of instruction-and what the psychological basis for any interaction might be. The present study demonstrates that successfully learning a foreign-language phonological contrast for pitch depends on an interaction between individual differences in perceptual abilities and the design of the training paradigm. Training from stimuli with high acoustic-phonetic variability is generally thought to improve learning; however, we found high-variability training enhanced learning only for individuals with strong perceptual abilities. Learners with weaker perceptual abilities were actually impaired by high-variability training relative to a low-variability condition. A second experiment assessing variations on the high-variability training design determined that the property of this learning environment most detrimental to perceptually weak learners is the amount of trialby-trial variability. Learners' perceptual limitations can thus override the benefits of high-variability training where trial-by-trial variability in other irrelevant acoustic-phonetic features obfuscates access to the target feature. These results demonstrate the importance of considering individual differences in pretraining aptitudes when evaluating the efficacy of any speech training paradigm.

Spoken language processing in noisy environments, a hallmark of the human brain, is subject to agerelated decline, even when peripheral hearing might be intact. The present study examines the cortical cerebral hemodynamics (measured by fMRI) associated with such processing in the aging brain. Younger and older subjects identified single words in quiet and in two multi-talker babble noise conditions (SNR 20 and −5 dB). Behaviorally, older and younger subjects did not show significant differences in the first two conditions but older adults performed less accurately in the SNR -5 condition. The fMRI results showed reduced activation in the auditory cortex but an increase in working memory and attention-related cortical areas (prefrontal and precuneus regions) in older subjects, especially in the SNR -5 condition. Increased cortical activities in general cognitive regions were positively correlated with behavioral performance in older listeners, suggestive of a compensatory strategy. Furthermore, inter-regional correlation revealed that while younger subjects showed a more streamlined cortical network of auditory regions in response to spoken word processing in noise, older subjects showed a more diffused network involving frontal and ventral brain regions. These results are consistent with the decline-compensation hypothesis, suggestive of its applicability to the auditory domain.

Peripheral and central structures along the auditory pathway contribute to speech processing and learning. However, because speech requires the use of functionally and acoustically complex sounds which necessitates high sensory and cognitive demands, long-term exposure and experience using these sounds is often attributed to the neocortex with little emphasis placed on subcortical structures. The present study examines changes in the auditory brainstem, specifically the frequency following response (FFR), as native English-speaking adults learn to incorporate foreign speech sounds (lexical pitch patterns) in word identification. The FFR presumably originates from the auditory midbrain, and can be elicited pre-attentively. We measured FFRs to the trained pitch patterns before and after training. Measures of pitch-tracking were then derived from the FFR signals. We found increased accuracy in pitch-tracking after training, including a decrease in the number of pitch-tracking errors and a refinement in the energy devoted to encoding pitch. Most interestingly, this change in pitch-tracking accuracy only occurred in the most acoustically complex pitch contour (dipping contour), which is also the least familiar to our English-speaking subjects. These results not only demonstrate the contribution of the brainstem in language learning and its plasticity in adulthood, but they also demonstrate the specificity of this contribution (i.e., changes in encoding only occurs in specific, least familiar stimuli, not all stimuli). Our findings complement existing data showing cortical changes after second language learning, and are consistent with models suggesting that brainstem changes resulting from perceptual learning are most apparent when acuity in encoding is most needed.