Browsing by Subject "EEG"

Objectives. There are only a few prior studies about brain functions while listening to live and improvised music. Yet, an EEG frequency band called alpha (8-10 Hz) has been shown to be connected to listening of music improvisation, but the connections between alpha and listening to improvised music are largely unknown. The progress of wireless mobile EEG devices makes recording EEG in this kind of tasks now easier. In this study we examine the feasibility of measuring EEG in a situation like this and the connection between alpha power and listening to partly improvised or familiar live music. Methods. In this study, EEG of 14 professional musicians and amateur musicians was recorded while they listened to familiar and unfamiliar pieces of music and partly improvised versions of those pieces performed live by a chamber trio. The subjects rated how improvised and interesting each of the four performances sounded. Data from posterior and midline electrodes were analyzed to define alpha power. Results and conclusions. There were no differences in alpha power between the performances. Listeners rated partly improvised performances more improvisatory, but there was no difference in how interesting the performances were rated. Studying music improvisation may help us to expand the knowledge of creativity. According to this study it is possible to study listeners’ brain functions with EEG during live music improvisation performances also outside the laboratory.

Objective: To contribute to the theory-building on hypnosis by studying the possible changes that hypnosis causes in the electroencephalographic (EEG) spectral power in highly hypnotisable individuals. In accordance with previous literature, hypnosis was hypothesised to cause an increase in theta (4–8 Hz) power and a change in gamma (25–45 Hz) power. Methods: Nine highly hypnotisable individuals (8 females) participated. Continuous EEG was recorded at ten electrodes during four conditions: prehypnosis, neutral hypnosis, hypnotic suggestion, and posthypnosis. During all conditions, the participants watched a monotonous video while sinusoidal tones following an oddball paradigm played silently in the background. The participants were instructed not to pay any attention to the tones, and in the suggestion-condition a suggestion to hear all tones as similar in pitch was given. Nine repeated-measures analyses of variance, one for each frequency range, were performed. For research questions 2 and 3, the participants were divided into two groups depending on their responsiveness to a hallucinatory suggestion in the screening phase, and the analyses were then run again. Results: No differences between conditions were found in the theta range, but a decrease was found in the gamma range during hypnosis compared with wakefulness (posthypnosis). Spectral power differences depending on responsiveness to the hallucinatory suggestion were also found. Conclusions: The findings support the hypothesis of changed gamma-frequency power during hypnosis, but not the theory of increased theta frequencies as a marker of hypnosis. A tentative theoretical connection between reduced peripheral awareness and reduced gamma power in hypnosis is presented.

Aim: So far, most of the cognitive neuroscience studies investigating the development of brain activity in childhood have made comparisons between different age groups and ignored the individual stage of cognitive development. Given the wide variation in the rate of cognitive development, this study argues that chronological age alone cannot explain the developmental changes in brain activity. This study demonstrates how Piaget's theory and information on child's individual stage of development can complement the age-related evaluations of brain oscillatory activity. In addition, the relationship between cognitive development and working memory is investigated. Method: A total of 33 children (17 11-year-olds, 16 14-year-olds) participated in this study. The study consisted of behavioural tests and an EEG experiment. Behavioral tests included two Piagetian tasks (the Volume and Density task, the Pendulum task) and Raven's Standard Progressive Matrices task. During EEG experiment, subjects performed a modified version of the Sternberg's memory search paradigm which consisted of an auditorily presented memory set of 4 words and a probe word following these. The EEG data was analyzed using the event-related desynchronization / synchronization (ERD/ERS) method. The Pendulum task was used to assess the cognitive developmental stage of each subject and to form four groups based on age (11- or 14-year-olds) and cognitive developmental stage (concrete or formal operational stage). Group comparisons between these four groups were performed for the EEG data. Results and conclusions: Both age- and cognitive stage-related differences in brain oscillatory activity were found between the four groups. Importantly, age-related changes similar to those reported by previous studies were found also in this study, but these changes were modified by developmental stage. In addition, the results support a strong link between working memory and cognitive development by demonstrating differences in memory task related brain activity and cognitive developmental stages. Based on these findings it is suggested that in the future, comparisons of development of brain activity should not be based only on age but also on the individual cognitive developmental stage.

Rapid learning or fast mapping reflects the human brain’s ability to form new memory traces to novel words during exposure without the need for a long overnight consolidation period before the word can be used in conversation. This ability to acquire new words almost instantaneously may very well reflect how well-tuned the human language systems are to the phonemes of the native language. However, the neural basis of rapid learning has been largely unknown until recent neuroimaging studies. In this study on adult learners (n = 15), I recorded brain’s event-related potentials elicited by three different types of auditory bi-syllabic stimuli (native words, native pseudowords and pseudowords with unfamiliar phonemes, all acoustically closely matched) in a passive EEG-recording session before and after subjects participated in two types of training conditions. In the attend condition, subjects listened to a flow of stimuli while pressing a button when a target stimulus appeared. In the articulation condition subjects repeated out loud the heard stimuli. An auditory memory recognition test was administered after training to allow the comparison of neural learning effects to observable change in behaviour. Larger evoked responses were expected to correlate with better performance in the recognition task. All analyses were time-locked to the onset of the second syllable (critical disambiguation point/recognition point). A two-peak waveform was observed to all stimuli after both conditions, with the earlier peak appearing circa 40 ms and the later peak circa 140 ms after second syllable onset. Unlike in similar previous studies where responses increased as a result of learning, all responses decreased in magnitude. No statistically significant differences between the conditions were observed. This may have been due to either the small sample size, test subject fatigue or suppression effects due to repetition, masking any possible learning effects. For the late peak, native pseudowords evoked significantly stronger responses than native words or non-native pseudowords. Performance in the memory recognition task was good (above chance for all stimuli in both conditions), and as such learning cannot be excluded even though statistically significant differences in the evoked responses were not found. Further research and re-exploration of the data acquired here utilising source modelling might enable to assess in more detail the effect of attentive listening vs. articulation in rapid learning.

Abstract: The EEG measurement protocol is standardized and in use globally. The skull is measured to ensure that the electrodes are placed in the correct position. Measurements are necessary because skull sizes and shapes are different. Studies for placing electroencephalograph (EEG) electrodes on a human head are typically introduced theoretically before students are granted the opportunity to practice. Due to the limited availability of EEG equipment and supervisory staff, students encounter shortened practical training sessions and lengthy waiting periods transitioning from theory to practical components. The main aim of this project was to create a learning environment with game technologies to help students study electrode placement during the idle time between theory lessons and practical training. We set out to determine whether students experienced some learning gain and if they had a positive experience with the learning environment. We simultaneously assessed if fuzzy feedback is preferred over exact feedback. Additionally, the aim was to make use of a design-based approach with the information from a User Experience Questionnaire (UEQ) the EEG-simulator. Our group developed and tested a digital learning application that provides a 3D model of a human head, on which learners can practice placing EEG electrodes. We followed a user-centric design science approach to ensure our application appeals to our target audience. We used an observational post-test only design with two experimental groups and a control group. We applied a widely accepted user experience questionnaire to ascertain which of our two feedback systems elicited the best user experience. We also qualitatively analyzed diaries the students kept, as they worked with the learning environment, to better understand future development options for further maximizing the environment’s learning benefit. The overall application was well-received, and students opined that the application significantly enhanced their practical session experience. Although the post-test evaluation showed no difference between the two experimental groups, the user experience questionnaire showed that the fuzzy feedback system was preferred over the exact feedback. Furthermore, it was evident that students who had not used the learning environment struggled more to come to terms with the practical session. The personal experience recording by the students revealed several suggested improvements to the learning environment. We conclude that, with further development, this EEG placement learning application could address the idle period between demonstration lessons and practical training. We also venture to state that fuzzy feedback is preferred because of the high-fidelity mimicry of real teacher feedback. The last part of the research was to develop the EEG simulator so that it will increase theory learning with a simulator, that works, and this is ongoing. We have developed the last EEG simulator version with AR (augmented reality) mobile version that can be used with any smart devices. The future work is to test EEG application and does application influence student's theory learning process.

Poor quality of sleep and the following health problems affecting daily life are in many cases caused by cognitive and physiological arousal resulted from a stressful event. Such stress detrimental to sleep may originate from psychosocial factors such as feelings of shame and social rejection. Our goal was to elucidate the impact of acute psychosocial stress occurring before bedtime on sleep macrostructure and the early night non-rapid eye movement sleep (NREMS). In addition, virtual reality solutions are emerging as options to simulate social threats in laboratory environments. We studied whether a virtual reality variation of a public speaking scenario was sufficient in producing a physiological stress response evident in heart rate variability (HRV) parameters. We compared two experimental groups of healthy young adults (n=34), which differed in the scenario completed within the virtual reality. The stress condition involved a public speaking simulation in front of an attentive virtual audience whereas the control condition involved listening to a neutral presentation in the same but empty virtual seminar room. The participants’ physiological responses were measured with a HRV monitor for 38 hours and the quality of sleep during the laboratory night following stress induction with electroencephalography (EEG). The examined early sleep period was divided into two separate cycles of NREMS, whose results were juxtaposed. For analysing frequency band activity during sleep, we processed the data from EEG with Fourier transformation to yield power spectral density values i.e. frequency activity values. Comparing the two conditions, we observed a distinct effect of stress both during the virtual public speaking scenario and in the subsequent early sleep in the participants from the stress group. We found a significant increase in heart rate and rising fluctuations in the LF/HF (HRV power spectrum high frequency/low frequency) ratio around the stress task period contrasting the results of the control condition, reflecting increased sympathetic tone in the stress group. In the following night, the percentage of stage N3 sleep significantly increased at the cost of N2 sleep during the first NREMS cycle in the stress condition, but this effect resolved in the second NREMS cycle where group differences were absent. As a key finding, the stress group exhibited higher beta frequency activity in proportion to delta activity throughout both cycles and sleep stages. This effect was significantly magnified in N3 sleep where the delta/beta activity ratio decreased in the stress group from cycle 1 to 2, indicating worsening quality of sleep as the night progressed. We reflected our results through a homeostatic point of view, where the increased high frequency beta activity at sleep onset and early sleep in the stress group might explain their increased N3 sleep duration in the first NREMS cycle. A stronger affinity for the important N3 sleep may be a sleep protective mechanism to counter the stress induced abnormally high frequency EEG activity at sleep onset and early sleep to ensure the restorative benefits of slow-wave activity.

Objectives. Perception of auditory pitch can be divided in to two dimensions of height and chroma. Tones of the same chroma, one or more octave intervals apart, sound similar. The octave interval is defined as the doubling of a tones fundamental frequency. However, in humans the perceptual octave slightly exceeds its mathematical counterpart. The objective of this study was to clarify the neural underpinnings responsible for the subjective experience of chroma and the enlarged octave. Methods. During all experiments adapter tones followed by probing tones were sequentially presented to participants (n=18). Adapter tones were used to activate neural populations and probing tones were used for measuring amplitude reductions (adaptation) in EEG derived event related potentials (ERPs) signalling overlapping neural population responses to adapter and probing tones. Participants were divided in to two groups with either sine tones or complex tones as adapters. 7 pitch separations between adapter and probe were used. Differences between different interval ERPs and effects of musical proficiency in both groups were analysed with mixed repeated measures analyses of variance. Measurements were fitted to a combined sinusoidal and linear pitch helix function. Source magnitude estimation was calculated to investigate hemispheric asymmetry. Results and conclusions. There was greater neural overlap between tones sharing the same chroma compared to tones one semitone apart. Periodicity independent adaptation indicated that pitch is not co-represented with stimulus spectrum in the human auditory cortex. Source magnitude analyses showed that N1 responses were stronger on the right auditory cortex. P2 amplitude showed stronger adaptation to enlarged octave intervals in comparison to exact mathematical octave intervals.

Tässä pro gradu -tutkielmassa on tarkasteltu aivosähkö- ja aivomagneettikäyrien amplitudien vaihteluiden vastaavuussuhteita koehenkilön suoriutumiseen audiovisuaalisten ärsykkeiden tarkkaavaisuustehtävissä. Aikaisemmista tutkimuksista tiedetään, että koehenkilön osumatarkkuus ei pysy vakiona koko tehtävän ajan, vaan on monesti jaksottunut valppauden ja herpaantumisen jaksoihin. Lisäksi osumatarkkuus koko kokeen ajalta on alhaisempi kuin lyhyen kalibraatiojakson ajalta mitattuna. Tämän intuitiiviseltä tuntuvan keskittymiskyvyn järkkymisen taustalla on esitetty olevan henkilön introspektiiviset ja mielenvaelteluun liittyvät kognitiiviset toiminnot. Ennen tätä tutkimusta on jäänyt kuitenkin osoittamatta osumatarkkuuden ailahtelun yhteys aivokuoren hermostollisen aktiivisuuden pitkällä ajalla autokorreloiviin muutoksiin lähdemallintamisella. Tämän pro gradun tutkimustulokset osoittavat, että näiden kahden lajin välillä on olemassa merkittävä korrelaatioyhteys. Lisäksi lepovaiheen aivotoiminnasta modaliteettispesifeillä tarkkaavaisuus- ja oletustilan verkoston alueilla voidaan ennustaa psykofyysisen suoriutumisen vaihteluja jatkuvan audiovisuaalisen ärsykekynnyksen tarkkaavaisuustehtävän aikana. Keskittymiskyvyn vaihtelun muutoksia hermostollisella tasolla ja näitä mahdollisesti ilmentäviä käyttäytymisen ailahteluja psykofyysisinä parametreinä, kuten osumatarkkuutena ja reaktionopeutena, voidaan luonnehtia skaalauslakianalyysilla. Ilmiön skaalaton käyttäytyminen heijastelee monimutkaisen järjestelmän taipumusta luoda sisäisiä vastaavuussuhteita eli autokorrelaatioita, jotka heikkenevät hitaammin ja ulottuvat kauemmaksi ajassa ja/tai paikassa kuin mitä alla piilevistä mekanismeista voidaan suoraan ennustaa. On havaittu, että osumatarkkuuden jaksottuminen ja spontaani aivotoiminta noudattavat potenssilain skaalauskäyttäytymistä ajan suhteen. Psykofyysisen ja hermostollisen skaalauslain mukaisen käyttäytymisen kvantifioimiseksi tässä opinnäytetyössä on käytetty vaihtelun ikkunallista autokorrelaatioanalyysiä, DFA:ta. DFA paljastaa ilmiön sisällä olevien peräkkäisten tapahtumien autokorrelaatioiden kestävyyden tarkasteluvälin kasvaessa. Skaalausluvut eli DFA-eksponentit on johdettu tässä kokeessa jatkuvan audiovisuaalisen ärsykekynnyksen tarkkaavaisuustehtävän ja levon aikana rekisteröidyistä aivosähkö- ja aivomagneettikäyräsignaalien verhokäyrästä sekä psykofyysisen osuma/huti -binäärisekvenssistä rakennetusta keinotekoisesta satunnaiskulun kaltaisesta käyrästä. Jatkuvat ärsykekynnystehtävät soveltuvat hyvin tarkkaavaisuuden top-down mekanismien tutkimiseen, koska heikoista, vain juuri ja juuri havaintokyvyn säteellä olevista ärsykkeistä seuraa verraten heikko bottom-up hermostovaste. Näin keskittymiskykyyn vaikuttavat top-down säätelymekanismit kuten motivaatio, päämäärät tai mielenvaeltelu eli spontaanilta vaikuttava aivotoiminta edustuu selkeämmin aivosähkö- ja -magneettikäyrissä. Aivokuoren kokonaisvaltaisen skaalautumisen lisäksi ollaan kiinnostuneita psykofyysisten ja hermostollisten vastaavuussuhteiden jakaumamallista tietyille aivoalueille. Mitattujen hermostollisten signaalien paikantaminen tarkalleen tietyille aivokuoren alueille aiheuttaa käänteisen ongelman, joka on ratkaistu tässä MNE -lähdemallintamisella. Lähdemallintamisen algoritmit tuottavat todennäköisimmän mallin aivokuoren alueista, joiden aktiivisuudella voidaan selittää mitatut MEEG signaalit. Mallintaminen on työn kriittinen vaihe, koska sillä yhdistetään neuroanatominen tieto fysiologisen ja psykofyysisen tiedon kanssa. Yksilötason data on käsitelty lopuksi ryhmätasolla tilastollisin menetelmin korrelaatiotulosten merkittävyyksien arvioimiseksi.

Objectives. Improvisation has so far been studied mainly from the perspective of the musicians and less is known about how improvisation affects the audience. The main objective of the present study is to find out how using an improvisatory approach in classical music performance affects 1) the subjective ratings for the music given by the audience, and 2) neural frontal theta activity of the audience, this activity being previously linked to attention, processing of surprising stimuli, and pleasant and strong emotional processes. We are also interested in how expertise in music affects the above mentioned reactions. Methods. Twelve participants, all of whom had received a considerable amount of musical training, took part in the study. A professional chamber music trio performed two versions of the same baroque music piece: once in a standard way without improvisation, and once with an improvisatory approach. The audience was familiar with the original piece in advance. The audience rated the pieces by their musical features (improvisatory, innovative, emotional, musical, brave and interesting). The participants’ EEG activation was measured during music, and theta band power was analyzed from the frontal midline electrodes of each participant. Results and conclusions. In line with hypothesis, the improvisatory piece was rated as more improvisatory and innovative, compared to the standard piece. In contrast, the standard piece was rated as more musical, this finding approaching statistical significance. Supporting the original hypothesis, the frontal theta power was stronger during the improvisatory piece almost statistically significantly across all members of the audience and significantly among the musicians (N=8). Stronger frontal theta power may reflect more focused attention as well as stronger and more pleasant emotional reactions among the listeners during improvisation. According to the present study, using an improvisatory approach in classical music performance seems to have a somewhat unique effect on the live audience, compared to a score-based performance. It seems that professional musicians may react to improvisatory music even more sensitively than the regular audience.

Objectives. This study aimed to clarify the brain-level processing of face stimuli by examining event related potentials. The purpose was to examine whether it is appropriate to make conclusions about the localization of brain-level processing of face expression and identity. Additionally, the study wanted to clarify whether there are observable differences between expression processing and does the intensity of the expression affect on the brain-level differentiation of expressions. Prior studies about the perception of face stimuli have been heavily focused on the modular view of the information processing system, in which every cognitive function has its own anatomical correlates and where the modules are clearly distinguishable from each other. The opposing view to this is the network-assumption in which the confines between modules are vague. Knowledge about these cognitive processes is crucial when new rehabilitation forms are being developed for people, from whom face perception is abnormal. Methods. 17 healthy test subjects took part in the study. In total, subjects were presented with 112 face stimuli, in which face expression and identity varied systematically. Based on prior studies, the event related potentials, which are known to be present in the perception of face stimuli were especially studied: the positive or negative fluctuations that occur 100, 170 and 250 milliseconds after the presentation of face stimulus (so called P1, N170 and N250 components). The effects of expressions and identities on the event related potentials were examined with traditional one-variable analysis (comparison of averages) as well as with multiple variable methods (comparison of correlations of distributions), which better expose the changes caused by face stimuli manipulations. Results and conclusions. The average amplitude and latency of event related potentials did not differe across conditions. The complex interactions between test conditions were exposed by forming 112 x 112 dissimilarity matrices of event related potentials. General linear model, which included eight regressors, was fitted into dissimilarity matrices. Fitted models were also compiled. In those, every every regressor was weighted with beta-coefficients at the time points of P1, N170 and N250 components. Based on the results, it is possible to assume that expression processing happens in an earlier phase than identity processing. Additionally, there was a robust interaction between expression and identity, which clarified the variation in the data. These results give support to the network-assumption in the perception of faces. However, the network-assumption does not deny modularity completely.