Noise sensitivity in the function and structure of the brain

Exposure to noise has a negative influence on human health, including an increased occurrence of cardiovascular diseases. Susceptibility to the harmful effects of noise can be further moderated by a personal trait called noise sensitivity (NS). It is not understood what makes some individuals more sensitive to noise than others. So far, the research on this topic has been largely limited to perceptual and population studies. The aim of this thesis was to broaden the understanding of NS by addressing its biological mechanisms. Thus, this thesis investigated the neuroanatomical correlates of NS and its effects on auditory processing. The thesis consists of three studies. The first study examines whether NS can be developed as the result of musical training (Study I). The other two studies investigate whether NS is reflected in the functioning of the central auditory system (Study II) and whether it is related to the morphology of cortical and subcortical brain structures (Study III). The research was conducted using questionnaires, combined magneto- and electroencephalography (MEG/EEG) and magnetic resonance imaging (MRI). The findings of this thesis suggest that NS moderates how and why individuals listen to music. However, NS is not associated with musical training and thus does not seem to relate to fine perceptual skills (Study I). An investigation of the central auditory processing in Study II, however, revealed compromised sound feature encoding and automatic discrimination skills in noise-sensitive individuals. Study III showed that NS is also associated with the structural organization of the brain. Noise-sensitive individuals were found to have enlarged volumes of the auditory cortical areas and hippocampus as well as thicker right anterior insular cortex. These results suggest that NS is related to the structures involved with auditory perceptual, emotional, and interoceptive processing. Overall, this thesis proposes that NS is not merely an attitudinal phenomenon but instead has underlying neuronal mechanisms.Altistuminen melulle vaikuttaa negatiivisesti ihmisten terveyteen, muun muassa kohonneena riskinä sydän- ja verisuonitaudeille. Meluherkkyys on persoonallisuuden piirre, joka voi vaikuttaa alttiuteen melusta koituville haitoille. Syytä sille, mikä tekee toisista herkempiä melulle, ei tiedetä. Tähän mennessä asiaa on selvitetty lähinnä melun havaintokykyä ja sen esiintymistä väestössä kartoittavien tutkimusten avulla. Tämän väitöskirjan tavoitteena oli lisätä tietoa meluherkkyyden biologisista mekanismeista. Väitöskirjassa tutkittiin meluherkkyyteen liittyviä aivojen rakenteita sekä meluherkkyyden vaikutusta kuulotiedon käsittelyyn. Väitöskirja koostuu kolmesta osatutkimuksesta. Ensimmäisessä tutkimuksessa selvitettiin, voiko meluherkkyys kehittyä musiikin harjoittelun seurauksena (Tutkimus I). Kahdessa muussa osatutkimuksessa selvitettiin, heijastuuko meluherkkyys aivojen kuulojärjestelmän toimintaan (Tutkimus II), ja liittyykö se aivokuoren ja sen alaisiin rakenteisiin (Tutkimus III). Tutkimukset suoritettiin käyttämällä kyselytutkimuksia, yhdistettyä aivosähkökäyrää ja sen magneettista vastinetta, eli elektro- ja magnetoenkefalografiaa (EEG/MEG), sekä aivojen magneettikuvausta (MRI). Tämän väitöskirjan tulosten mukaan meluherkkyys vaikuttaa siihen, miten ja miksi ihmiset kuuntelevat musiikkia. Meluherkkyys ei kuitenkaan liity musiikin harjoitteluun eikä täten liene yhteydessä hienovaraiseen kuulohavaintokykyyn (Tutkimus I). Tutkimus II kuitenkin paljasti, että äänten erottelukyky ja äänipiirteiden koodaus aivoissa on heikentynyttä meluherkillä yksilöillä. Tutkimuksessa III osoitettiin, että meluherkkyys on myös yhteydessä aivorakenteiden järjestäytymiseen. Meluherkillä löydettiin suurentunut kuuloaivokuoren ja hippokampuksen tilavuus sekä paksumpi oikean etuaivopuoliskon aivosaari. Näiden tulosten mukaan meluherkkyys on yhteydessä rakenteisiin, jotka osallistuvat äänten havaitsemiseen sekä niiden tunneperäistä ja elimellistä tietoa välittävään tiedonkäsittelyyn. Kaiken kaikkiaan tässä väitöskirjassa esitetään, että meluherkkyydellä on hermostollista taustaa eikä se ole pelkästään negatiivinen asenne melua kohtaan

Applying Acoustical and Musicological Analysis to Detect Brain Responses to Realistic Music: A Case Study

Music information retrieval (MIR) methods offer interesting possibilities for automatically identifying time points in music recordings that relate to specific brain responses. However, how the acoustical features and the novelty of the music structure affect the brain response is not yet clear. In the present study, we tested a new method for automatically identifying time points of brain responses based on MIR analysis. We utilized an existing database including brain recordings of 48 healthy listeners measured with electroencephalography (EEG) and magnetoencephalography (MEG). While we succeeded in capturing brain responses related to acoustical changes in the modern tango piece Adios Nonino, we obtained less reliable brain responses with a metal rock piece and a modern symphony orchestra musical composition. However, brain responses might also relate to the novelty of the music structure. Hence, we added a manual musicological analysis of novelty in the musical structure to the computational acoustic analysis, obtaining strong brain responses even to the rock and modern pieces. Although no standardized method yet exists, these preliminary results suggest that analysis of novelty in music is an important aid to MIR analysis for investigating brain responses to realistic music.Peer reviewe

Extracting human cortical responses to sound onsets and acoustic feature changes in real music, and their relation to event rate

Evoked cortical responses (ERs) have mainly been studied in controlled experiments using simplified stimuli. Though, an outstanding question is how the human cortex responds to the complex stimuli encountered in realistic situations. Few electroencephalography (EEG) studies have used Music Information Retrieval (MIR) tools to extract cortical P1/N1/P2 to acoustical changes in real music. However, less than ten events per music piece could be detected leading to ERs due to limitations in automatic detection of sound onsets. Also, the factors influencing a successful extraction of the ERs have not been identified. Finally, previous studies did not localize the sources of the cortical generators. This study is based on an EEG/MEG dataset from 48 healthy normal hearing participants listening to three real music pieces. Acoustic features were computed from the audio signal of the music with the MIR Toolbox. To overcome limits in automatic methods, sound onsets were also manually detected. The chance of obtaining detectable ERs based on ten randomly picked onset points was less than 1:10,000. For the first time, we show that naturalistic P1/N1/P2 ERs can be reliably measured across 100 manually identified sound onsets, substantially improving the signal-to-noise level compared to 2.5 Hz). Furthermore, during monophonic sections of the music only P1/P2 were measurable, and during polyphonic sections only N1. Finally, MEG source analysis revealed that naturalistic P2 is located in core areas of the auditory cortex.Peer reviewe

Fractionating auditory priors : A neural dissociation between active and passive experience of musical sounds

Learning, attention and action play a crucial role in determining how stimulus predictions are formed, stored, and updated. Years-long experience with the specific repertoires of sounds of one or more musical styles is what characterizes professional musicians. Here we contrasted active experience with sounds, namely long-lasting motor practice, theoretical study and engaged listening to the acoustic features characterizing a musical style of choice in professional musicians with mainly passive experience of sounds in laypersons. We hypothesized that long-term active experience of sounds would influence the neural predictions of the stylistic features in professional musicians in a distinct way from the mainly passive experience of sounds in laypersons. Participants with different musical backgrounds were recruited: professional jazz and classical musicians, amateur musicians and non-musicians. They were presented with a musical multi-feature paradigm eliciting mismatch negativity (MMN), a prediction error signal to changes in six sound features for only 12 minutes of electroencephalography (EEG) and magnetoencephalography (MEG) recordings. We observed a generally larger MMN amplitudes-indicative of stronger automatic neural signals to violated priors-in jazz musicians (but not in classical musicians) as compared to non-musicians and amateurs. The specific MMN enhancements were found for spectral features (timbre, pitch, slide) and sound intensity. In participants who were not musicians, the higher preference for jazz music was associated with reduced MMN to pitch slide (a feature common in jazz music style). Our results suggest that long-lasting, active experience of a musical style is associated with accurate neural priors for the sound features of the preferred style, in contrast to passive listening.Peer reviewe

A window into the brain mechanisms associated with noise sensitivity

Noise sensitive individuals are more likely to experience negative emotions from unwanted sounds and they show greater susceptibility to adverse effects of noise on health. Noise sensitivity does not originate from dysfunctions of the peripheral auditory system, and it is thus far unknown whether and how it relates to abnormalities of auditory processing in the central nervous system. We conducted a combined electroencephalography and magnetoencephalography (M/EEG) study to measure neural sound feature processing in the central auditory system in relation to the individual noise sensitivity. Our results show that high noise sensitivity is associated with altered sound feature encoding and attenuated discrimination of sound noisiness in the auditory cortex. This finding makes a step towards objective measures of noise sensitivity instead of self-evaluation questionnaires and the development of strategies to prevent negative effects of noise on the susceptible population.Peer reviewe

Comparing the Performance of Popular MEG/EEG Artifact Correction Methods in an Evoked-Response Study

We here compared results achieved by applying popular methods for reducing artifacts in magnetoencephalography (MEG) and electroencephalography (EEG) recordings of the auditory evoked Mismatch Negativity (MMN) responses in healthy adult subjects. We compared the Signal Space Separation (SSS) and temporal SSS (tSSS) methods for reducing noise from external and nearby sources. Our results showed that tSSS reduces the interference level more reliably than plain SSS, particularly for MEG gradiometers, also for healthy subjects not wearing strongly interfering magnetic material. Therefore, tSSS is recommended over SSS. Furthermore, we found that better artifact correction is achieved by applying Independent Component Analysis (ICA) in comparison to Signal Space Projection (SSP). Although SSP reduces the baseline noise level more than ICA, SSP also significantly reduces the signal-slightly more than it reduces the artifacts interfering with the signal. However, ICA also adds noise, or correction errors, to the wave form when the signal-to-noise ratio (SNR) in the original data is relatively low-in particular to EEG and to MEG magnetometer data. In conclusion, ICA is recommended over SSP, but one should be careful when applying ICA to reduce artifacts on neurophysiological data with relatively low SNR.Peer reviewe

Maladaptive and adaptive emotion regulation through music : a behavioral and neuroimaging study of males and females

Music therapists use guided affect regulation in the treatment of mood disorders. However, self-directed uses of music in affect regulation are not fully understood. Some uses of music may have negative effects on mental health, as can non music regulation strategies, such as rumination. Psychological testing and functional magnetic resonance imaging (fMRI) were used explore music listening strategies in relation to mental health. Participants (n = 123) were assessed for depression, anxiety and Neuroticism, and uses of Music in Mood Regulation (MMR). Neural responses to music were measured in the medial prefrontal cortex (mPFC) in a subset of participants (n = 56). Discharge, using music to express negative emotions, related to increased anxiety and Neuroticism in all participants and particularly in males. Males high in Discharge showed decreased activity of mPFC during music listening compared with those using less Discharge. Females high in Diversion, using music to distract from negative emotions, showed more mPFC activity than females using less Diversion. These results suggest that the use of Discharge strategy can be associated with maladaptive patterns of emotional regulation, and may even have long-term negative effects on mental health. This finding has real-world applications in psychotherapy and particularly in clinical music therapy.Peer reviewe

Interoception in the sensory sensitivities: Evidence from the auditory domain

In his Discussion paper, Ward brakes important ground for the development of a framework for understanding the mechanisms underlying individual differences in sensory sensitivities across sensory domains. In this commentary, we would like to elaborate and highlight the role of interoception in sensory sensitivities focusing on the latest neuroimaging evidence drawn from research on sensitivities to auditory stimulation

On the Association Between Musical Training, Intelligence and Executive Functions in Adulthood

Converging evidence has demonstrated that musical training is associated with improved perceptual and cognitive skills, including executive functions and general intelligence, particularly in childhood. In contrast, in adults the relationship between cognitive performance and musicianship is less clear and seems to be modulated by a number of background factors, such as personality and socio-economic status. Aiming to shed new light on this topic, we administered the Wechsler Adult Intelligence Scale III (WAIS-III), the Wechsler Memory Scale III (WMS-III), and the Stroop Test to 101 Finnish healthy adults grouped according to their musical expertise (non-musicians, amateurs, and musicians). After being matched for socio-economic status, personality traits and other demographic variables, adult musicians exhibited higher cognitive performance than non-musicians in all the mentioned measures. Moreover, linear regression models showed significant positive relationships between executive functions (working memory and attention) and the duration of musical practice, even after controlling for intelligence and background variables, such as personality traits. Hence, our study offers further support for the association between cognitive abilities and musical training, even in adulthood.Peer reviewe

Intelligence and Music: Lower Intelligent Quotient Is Associated With Higher Use of Music for Experiencing Strong Sensations

Intelligence is a key psychological feature associated to emotion and perception. Listening to music is often linked to emotional experience and sensation seeking (SS), traits that have been shown overall negatively correlated with intelligence. In a sample of 53 musicians and 54 non-musicians, we assessed the use of music for experiencing strong emotions through the Music in Mood Regulation (MMR) and the intelligence quotient (IQ) by using the Wechsler Adult Intelligence Scale III (WAIS-III). We found a negative correlation between the full IQ score and the use of music for SS in both musician and non-musician groups. Furthermore, the use of music for SS was negatively correlated with Verbal IQ in musicians, and with Performance IQ in non-musicians. Our findings indicate that less intelligent individuals make a higher use of music for experiencing strong sensations than more intelligent ones. Furthermore, this association is modulated by the individual musical expertise