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.

Objectives: Mental health problems as well as chronic stress and worries have been shown to have an established connection to sleep quality, but the individual effects of acute, stressful situations encountered in everyday life have received less attention. Rapid eye movement (REM) sleep has a hypothesized role in the processing of emotional memories and may therefore be affected by daytime acute stress. In experimental animal models and non-experimental human studies on healthy subjects acute stress has been associated with increases in REM sleep spectral power in the theta and beta ranges. The aim of this study was to investigate in an experimental setting utilizing virtual reality, whether an acute stress experience influences REM spectral power at these frequency ranges. Methods: Two groups of healthy young adults (N=31, 61 % female, mean age 25.5 years, SD = 3.46) underwent stress inducing or neutral virtual reality scenarios after which they spent the night at a sleep laboratory where their brain activity during sleep was measured with electroencephalography (EEG). To analyse the differences in theta and beta frequency activity during REM sleep, the EEG signal was Fourier transformed to yield power spectral density (PSD) values. Results: Statistical analysis of PSD values revealed that participants in the stress condition exhibited higher REM sleep theta power than controls when controlling for the effects of sex and age. Additionally, sex was found to have a statistically significant effect on REM sleep theta and beta power, with females exhibiting higher power. Age had a negative relationship with spectral power at the theta range, as well as with central low and high beta power. Conclusions: The finding that experimentally manipulated acute stress increases REM sleep theta power during the following night indicates the importance of REM sleep theta activity in the adaptive processing of acute stress, possibly due to the emotional processing of the stressful memory. This study also underlines the importance of sex and age in understanding the relationship between acute stress and REM sleep.

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.

Epilepsia on sairaus, joka ilmenee suurentuneena riskinä saada epileptisiä kohtauksia pitkällä aikavälillä. Tässä tutkielmassa selvitettiin, kuinka moni tutkimukseen otetuista potilaista sai epilepsiadiagnoosin ja näistä diagnooseista selvitettiin epilepsioiden etiologiat. Tutkittiin myös anamneesin tietojen ja tutkimustulosten yhteyttä epilepsian kehittymiseen. Tämän retrospektiivisen tutkimuksen potilaat olivat tulleet EEG-tutkimukseen Helsingin Uuteen lastensairaalaan ensikohtauksen tai kohtausepäilyn takia. Anamneesin tietojen ja tutkimustulosten yhteyttä arvioitiin khiin neliötestillä ja iän yhteyttä arvioitiin kahden riippumattoman otoksen t-testillä. Tutkimukseen otettiin mukaan 478 potilasta ja 115 näistä potilaista sai epilepsiadiagnoosin seuranta-aikana. Kehittyneistä epilepsioista geneettiset ja rakenteelliset syyt aiheuttivat suurimman osan epilepsioista. Varma epileptinen kohtausoire, akuutti altistava tekijä, akuuttilääkityksen tarve, neurologinen perussairaus, epänormaali EEG, piikit tai purkaukset EEG:ssä ja EEG:n aikainen epileptinen kohtaus olivat tilastollisesti merkittäviä epilepsian kehittymiselle. Epilepsiaan sairastuneet potilaat olivat keskimäärin vanhempia kuin ne, jotka eivät sairastuneet. Potilaille kehittyneiden epilepsiamuotojen jakauma eroaa maailmanlaajuisesta jakaumasta, mutta käytetyt tutkimusmenetelmät ja tutkimukseen sijainti selittävät paljolti tämän eron. Muut samasta aiheesta tehdyt tutkimukset tukevat tämän tutkimuksen tuloksia epilepsian riskiä kasvattavista tekijöistä. Yksikään näistä tekijöistä ei kuitenkaan ole varma viite epilepsian kehittymiselle.

Temporal lobe epilepsy (TLE) is a prevalent and debilitating neurological disorder that significantly impacts the quality of life of affected individuals. Despite advances in treatment, many patients remain resistant to current therapies, underscoring the need for novel diagnostic and therapeutic approaches. This study investigates the potential of functional ultrasound imaging (fUS) to characterise the dynamics of the pilocarpine model of TLE in mice, aiming to provide insights into acute seizure induction, latent stage progression, and antiepileptic drug (AED) screening. Using an optimised pilocarpine protocol, we induced status epilepticus in anaesthetised head-fixed mice and monitored the progression of epilepsy through various stages using fUS and telemetric EEG. Our findings demonstrate that fUS effectively captures cerebral blood volume changes and functional connectivity (FC) alterations during acute SE induction, with significant increases in specific brain regions such as the hippocampus, thalamus, and sensory-motor cortex. Notably, rhythmic peaks in the power Doppler (PD) signal were observed during pilocarpine administration, suggesting neuronal rhythmicity and increased synchronicity between brain regions. Despite a decrease in global PD signal following diazepam administration, FC remained elevated, indicating persistent network reorganisation. In the chronic TLE induction protocol, fUS revealed significant FC alterations during the latent stage, particularly between the hippocampus, thalamus, and cortical regions. These changes were not observed in the early latent stage, suggesting a delayed mechanism of network reorganisation. Our results also highlight variability in the development of spontaneous recurrent seizures among individual animals, emphasising the need for both group and individual analyses. This study demonstrates the first use of fUS in capturing real-time dynamics of the pilocarpine model of TLE progression and provides a novel methodology for AED screening. The findings help further characterise FC alterations in the pilocarpine model and underscore the potential of fUS as a powerful tool for investigating epilepsy and developing more effective treatments, ultimately benefiting patients with drug resistant TLE.