Impact of major and minor mode on EEG frequency range activities of music processing as a function of expertise.

Processing western tonal music may yield distinct brain responses depending on the mode of the musical compositions. Although subjective feelings in response to major and minor mode are well described, the underlying brain mechanisms and their development with increasing expertise have not been thoroughly examined. Using high-density electroencephalography, the present study investigated neuronal activities in the frequency domain in response to polyphone musical compositions in major and minor mode in non-musicians, amateurs and experts. During active listening decrease of theta- and gamma-frequency range activities occurred with increasing expertise in right posterior regions, possibly reflecting enhanced processing efficiency. Moreover, minor and major compositions distinctively modulated synchronization of neuronal activities in high frequency ranges (beta and gamma) in frontal regions, with increased activity in response to minor compositions in musicians and in experts in particular. These results suggest that high-frequency electroencephalographic (EEG) activities carry information about musical mode, showing gradual increase of processing efficiency and sensitivity with musical expertise.

40Hz-Transcranial alternating current stimulation (tACS) selectively modulates speech perception.

The present study investigated the functional relevance of gamma oscillations for the processing of rapidly changing acoustic features in speech signals. For this purpose we analyzed repetition-induced perceptual learning effects in 18 healthy adult participants. The participants received either 6Hz or 40Hz tACS over the bilateral auditory cortex, while repeatedly performing a phoneme categorization task. In result, we found that 40Hz tACS led to a specific alteration in repetition-induced perceptual learning. While participants in the non-stimulated control group as well as those in the experimental group receiving 6Hz tACS considerably improved their perceptual performance, the application of 40Hz tACS selectively attenuated the repetition-induced improvement in phoneme categorization abilities. Our data provide causal evidence for a functional relevance of gamma oscillations during the perceptual learning of acoustic speech features. Moreover, we demonstrate that even less than twenty minutes of alternating current stimulation below the individual perceptual threshold is sufficient to affect speech perception. This finding is relevant in that this novel approach might have implications with respect to impaired speech processing in dyslexics and older adults.

Age-Related Neural Oscillation Patterns During the Processing of Temporally Manipulated Speech.

This EEG-study aims to investigate age-related differences in the neural oscillation patterns during the processing of temporally modulated speech. Viewing from a lifespan perspective, we recorded the electroencephalogram (EEG) data of three age samples: young adults, middle-aged adults and older adults. Stimuli consisted of temporally degraded sentences in Swedish-a language unfamiliar to all participants. We found age-related differences in phonetic pattern matching when participants were presented with envelope-degraded sentences, whereas no such age-effect was observed in the processing of fine-structure-degraded sentences. Irrespective of age, during speech processing the EEG data revealed a relationship between envelope information and the theta band (4-8 Hz) activity. Additionally, an association between fine-structure information and the gamma band (30-48 Hz) activity was found. No interaction, however, was found between acoustic manipulation of stimuli and age. Importantly, our main finding was paralleled by an overall enhanced power in older adults in high frequencies (gamma: 30-48 Hz). This occurred irrespective of condition. For the most part, this result is in line with the Asymmetric Sampling in Time framework (Poeppel in Speech Commun 41:245-255, 2003), which assumes an isomorphic correspondence between frequency modulations in neurophysiological patterns and acoustic oscillations in spoken language. We conclude that speech-specific neural networks show strong stability over adulthood, despite initial processes of cortical degeneration indicated by enhanced gamma power. The results of our study therefore confirm the concept that sensory and cognitive processes undergo multidirectional trajectories within the context of healthy aging.

Electrophysiological evidence for a specific neural correlate of musical violation expectation in primary-school children.

The majority of studies on music processing in children used simple musical stimuli. Here, primary schoolchildren judged the appropriateness of musical closure in expressive polyphone music, while high-density electroencephalography was recorded. Stimuli ended either regularly or contained refined in-key harmonic transgressions at closure. The children discriminated the transgressions well above chance. Regular and transgressed endings evoked opposite scalp voltage configurations peaking around 400ms after stimulus onset with bilateral frontal negativity for regular and centro-posterior negativity (CPN) for transgressed endings. A positive correlation could be established between strength of the CPN response and rater sensitivity (d-prime). We also investigated whether the capacity to discriminate the transgressions was supported by auditory domain specific or general cognitive mechanisms, and found that working memory capacity predicted transgression discrimination. Latency and distribution of the CPN are reminiscent of the N400, typically observed in response to semantic incongruities in language. Therefore our observation is intriguing, as the CPN occurred here within an intra-musical context, without any symbols referring to the external world. Moreover, the harmonic in-key transgressions that we implemented may be considered syntactical as they transgress structural rules. Such structural incongruities in music are typically followed by an early right anterior negativity (ERAN) and an N5, but not so here. Putative contributive sources of the CPN were localized in left pre-motor, mid-posterior cingulate and superior parietal regions of the brain that can be linked to integration processing. These results suggest that, at least in children, processing of syntax and meaning may coincide in complex intra-musical contexts.

Long-term exposure to music enhances the sensitivity of the auditory system in children.

This event-related brain potential study aims to contribute to the present debate regarding the effect of musical training on the maturation of the human auditory nervous system. To address this issue, we recorded the mismatch negativity (MMN) evoked by violin and pure sine-wave tones in a group of 7.5- to 12-year-old children who had either several years of musical experience with Suzuki violin lessons, or no musical training. The strength of the MMN responses to violin tones evident in the Suzuki students clearly surpassed responses in controls; the reverse pattern was observed for sine-wave tones. Suzuki students showed significantly shorter MMN latencies to violin tones than to pure tones; the MMN latency did not differ significantly between pure tones and violin sounds in the control group. Thus, our data provide general evidence of how and to what extent extensive musical experience affects the maturation of human auditory function at multiple levels, namely, accuracy and speed of auditory discrimination processing. Our findings add to the present understanding of neuroplastic organization and function of the mammalian nervous system. Furthermore, behavioural recordings obtained from the participating children provide corroborating evidence for a relationship between the duration and intensity of training, the specific sensitivity to instrumental timbre, and pitch recognition abilities.

Absolute pitch--functional evidence of speech-relevant auditory acuity.

Absolute pitch (AP) has been shown to be associated with morphological changes and neurophysiological adaptations in the planum temporale, a cortical area involved in higher-order auditory and speech perception processes. The direct link between speech processing and AP has hitherto not been addressed. We provide first evidence that AP compared with relative pitch (RP) ability is associated with significantly different hemodynamic responses to complex speech sounds. By systematically varying the lexical and/or prosodic information of speech stimuli, we demonstrated consistent activation differences in AP musicians compared with RP musicians and nonmusicians. These differences relate to stronger activations in the posterior part of the middle temporal gyrus and weaker activations in the anterior mid-part of the superior temporal gyrus. Furthermore, this pattern is considerably modulated by the auditory acuity of AP. Our results suggest that the neural underpinnings of pitch processing expertise exercise a strong influence on propositional speech perception (sentence meaning).