Intra-individual Reliability of Voice- and Music-elicited Responses and their Modulation by Expertise.

A growing number of functional neuroimaging studies have identified regions within the temporal lobe, particularly along the planum polare and planum temporale, that respond more strongly to music than other types of acoustic stimuli, including voice. This "music preferred" regions have been reported using a variety of stimulus sets, paradigms and analysis approaches and their consistency across studies confirmed through meta-analyses. However, the critical question of intra-subject reliability of these responses has received less attention. Here, we directly assessed this important issue by contrasting brain responses to musical vs. vocal stimuli in the same subjects across three consecutive fMRI runs, using different types of stimuli. Moreover, we investigated whether these music- and voice-preferred responses were reliably modulated by expertise. Results demonstrated that music-preferred activity previously reported in temporal regions, and its modulation by expertise, exhibits a high intra-subject reliability. However, we also found that activity in some extra-temporal regions, such as the precentral and middle frontal gyri, did depend on the particular stimuli employed, which may explain why these are less consistently reported in the literature. Taken together, our findings confirm and extend the notion that specific regions in the brain consistently respond more strongly to certain socially-relevant stimulus categories, such as faces, voices and music, but that some of these responses appear to depend, at least to some extent, on the specific features of the paradigm employed.

Effects of musical expertise on oscillatory brain activity in response to emotional sounds.

Emotions can be conveyed through a variety of channels in the auditory domain, be it via music, non-linguistic vocalizations, or speech prosody. Moreover, recent studies suggest that expertise in one sound category can impact the processing of emotional sounds in other sound categories as they found that musicians process more efficiently emotional musical and vocal sounds than non-musicians. However, the neural correlates of these modulations, especially their time course, are not very well understood. Consequently, we focused here on how the neural processing of emotional information varies as a function of sound category and expertise of participants. Electroencephalogram (EEG) of 20 non-musicians and 17 musicians was recorded while they listened to vocal (speech and vocalizations) and musical sounds. The amplitude of EEG-oscillatory activity in the theta, alpha, beta, and gamma band was quantified and Independent Component Analysis (ICA) was used to identify underlying components of brain activity in each band. Category differences were found in theta and alpha bands, due to larger responses to music and speech than to vocalizations, and in posterior beta, mainly due to differential processing of speech. In addition, we observed greater activation in frontal theta and alpha for musicians than for non-musicians, as well as an interaction between expertise and emotional content of sounds in frontal alpha. The results reflect musicians' expertise in recognition of emotion-conveying music, which seems to also generalize to emotional expressions conveyed by the human voice, in line with previous accounts of effects of expertise on musical and vocal sounds processing.

Optimal measurements of hemodynamic response latency in fNIRS using the jackknife approach.

Functional near-infrared spectroscopy (fNIRS) permits measurements of changes in the concentration of oxygenated and deoxygenated hemoglobin, typically with a higher sampling rate than with other imaging methods based on the hemodynamic response. We examined the potential of the fNIRS technique to estimate variations in the latency of hemodynamic responses to experimental events and sought optimal methods to maximize the reliability and reproducibility of latency effects. We used Monte Carlo simulations using subsamples of real fNIRS measures to estimate the statistical power of different approaches (such as fixed threshold, percent of peak, fractional-area latency, for both individual-subject estimates and estimates from jackknife averages) to detect a known simulated latency shift. The simulations used measures of hemodynamic responses in the temporal lobe from two groups of young adult participants who listened to auditory stimuli, one with a blocked presentation design and one with an event-related design. We estimated the relative sensitivity of different latency measures and approaches to the measurement of latency effects of different magnitudes using realistic noise and signal-to-noise characteristics. In general, the jackknife approach provided the greatest statistical power to detect a known latency shift, without inflation of Type I error.

The specificity of neural responses to music and their relation to voice processing: an fMRI-adaptation study.

Several studies have identified, using functional magnetic resonance imaging (fMRI), a region within the superior temporal gyrus that preferentially responds to musical stimuli. However, in most cases, significant responses to other complex stimuli, particularly human voice, were also observed. Thus, it remains unknown if the same neurons respond to both stimulus types, albeit with different strengths, or whether the responses observed with fMRI are generated by distinct, overlapping neural populations. To address this question, we conducted an fMRI experiment in which short music excerpts and human vocalizations were presented in a pseudo-random order. Critically, we performed an adaptation-based analysis in which responses to the stimuli were analyzed taking into account the category of the preceding stimulus. Our results confirm the presence of a region in the anterior STG that responds more strongly to music than voice. Moreover, we found a music-specific adaptation effect in this area, consistent with the existence of music-preferred neurons. Lack of differences between musicians and non-musicians argues against an expertise effect. These findings provide further support for neural separability between music and speech within the temporal lobe.

Music listening engages specific cortical regions within the temporal lobes: differences between musicians and non-musicians.

Music and speech are two of the most relevant and common sounds in the human environment. Perceiving and processing these two complex acoustical signals rely on a hierarchical functional network distributed throughout several brain regions within and beyond the auditory cortices. Given their similarities, the neural bases for processing these two complex sounds overlap to a certain degree, but particular brain regions may show selectivity for one or the other acoustic category, which we aimed to identify. We examined 53 subjects (28 of them professional musicians) by functional magnetic resonance imaging (fMRI), using a paradigm designed to identify regions showing increased activity in response to different types of musical stimuli, compared to different types of complex sounds, such as speech and non-linguistic vocalizations. We found a region in the anterior portion of the superior temporal gyrus (aSTG) (planum polare) that showed preferential activity in response to musical stimuli and was present in all our subjects, regardless of musical training, and invariant across different musical instruments (violin, piano or synthetic piano). Our data show that this cortical region is preferentially involved in processing musical, as compared to other complex sounds, suggesting a functional role as a second-order relay, possibly integrating acoustic characteristics intrinsic to music (e.g., melody extraction). Moreover, we assessed whether musical experience modulates the response of cortical regions involved in music processing and found evidence of functional differences between musicians and non-musicians during music listening. In particular, bilateral activation of the planum polare was more prevalent, but not exclusive, in musicians than non-musicians, and activation of the right posterior portion of the superior temporal gyrus (planum temporale) differed between groups. Our results provide evidence of functional specialization for music processing in specific regions of the auditory cortex and show domain-specific functional differences possibly correlated with musicianship.

The effects of emotion on memory for music and vocalisations.

Music is a powerful tool for communicating emotions which can elicit memories through associative mechanisms. However, it is currently unknown whether emotion can modulate memory for music without reference to a context or personal event. We conducted three experiments to investigate the effect of basic emotions (fear, happiness, and sadness) on recognition memory for music, using short, novel stimuli explicitly created for research purposes, and compared them with nonlinguistic vocalisations. Results showed better memory accuracy for musical clips expressing fear and, to some extent, happiness. In the case of nonlinguistic vocalisations we confirmed a memory advantage for all emotions tested. A correlation between memory accuracy for music and vocalisations was also found, particularly in the case of fearful expressions. These results confirm that emotional expressions, particularly fearful ones, conveyed by music can influence memory as has been previously shown for other forms of expressions, such as faces and vocalisations.

Effects of rTMS on Parkinson's disease: a longitudinal fMRI study.

Parkinson's disease is a movement disorder whose principal symptoms are tremor, rigidity, bradykinesia and postural instability. Initially, drugs like L: -dopa or dopaminergic agonists are able to control these symptoms, but with the progress of the disease these drugs become less effective. Previous studies have reported that repetitive transcranial magnetic stimulation (rTMS) can improve these motor symptoms. The objective of this study was to investigate the neural mechanisms through which 25 Hz rTMS may improve motor symptoms in Parkinson's disease. In a double-blind placebo-controlled study, we evaluated the effects of 25 Hz. rTMS in 10 Parkinson's disease patients. Fifteen rTMS sessions were performed over the primary cortex on both hemispheres (one after the other) during a 12-week period. The patients were studied using functional magnetic resonance imaging during performance of a simple tapping and a complex tapping task, 1 week before the administration of the first rTMS session and just after the last session. rTMS improved bradykinesia, while functional magnetic resonance imaging showed different cortical patterns in prefrontal cortex when patients performed the complex tapping test. Furthermore, the improvement in bradykinesia is associated with caudate nucleus activity increases in simple tapping. Finally, we observed a relative change in functional connectivity between the prefrontal areas and the supplementary motor area after rTMS. These results show a potential beneficial effect of repetitive transcranial magnetic stimulation on bradykinesia in Parkinson's disease which is substantiated by neural changes observed in functional magnetic resonance imaging.

Sensitivity to voice in human prefrontal cortex.

We report two functional MRI (fMRI) experiments showing sensitivity to human voice in a region of human left inferior prefrontal cortex, pars orbitalis. The voice-enhanced response was observed for speech as well as non-linguistic vocalizations and was stronger for emotional than neutral vocalizations. This region could constitute a human prefrontal auditory domain similar to the one recently identified in the macaque brain.

Is voice processing species-specific in human auditory cortex? An fMRI study.

Recent studies suggested a sensitivity of regions of the human superior temporal sulcus (STS) to the sound of the human voice. However, the question of the species specificity of this response is still open. Healthy adult volunteers were scanned in an event-related fMRI design to compare responses in the STS to human and animal vocalizations, as well as to control nonvocal sounds (e.g., musical instruments). Bilateral activation of anterior STS was observed for human vocalizations, when contrasted with both nonvocal sounds and animal vocalizations. Animal vocalizations, compared to nonvocal sounds, elicited a more restricted left STS activation, although this region responded even more strongly to human vocalizations. This study provides the first evidence suggesting a species specificity in STS responses to vocalizations in humans.