Magnetoencephalographic investigations of human primary auditory cortex responses to multiple amplitude modulated tones

Der zeitlichen Verläufe von Sprach- oder Musikklängen enthalten Amplitudenuktuationen mit unterschiedlichen Rhythmen die Träger der Information sind. Unsere Studie liefert wertvolle neue Erkenntnisse darüber, wie und in welcher Hirnregion komplexe Töne verarbeitet werden und mit anderen Komponenten des zentralen auditorischen Kortex interagieren. Die 40 Hz SSR hat sich dabei als wertvoller Parameter bei der Erforschung von Sprachverarbeitung und Störungen des zentralen Kortex erwiesen. Ein reiner Ton, mit zwei Sinusschwingungen von 38 und 40 Hz moduliert, wird wahrgenommen als eine 2 Hz Schwankung der Lautheit und eine Rauhigkeit, die den Modulationsfrequenzen bei 40 Hz entspricht. Korrespondierende SSRs bei 2, 38 und 40 Hz wurden mit dem MEG erfasst, das die Lokalisation überlappender Quellen im primären auditorischen Kortex ermöglichte. Der allgemeinere Fall mehrfacher AM Töne mit verschiedenen Trägerfrequenzen zeigte, dass die Antwort auf einen AM Ton unterdrückt wird, wenn ein zweiter AM Stimulus gleichzeitig dargeboten wird. Die Ergebnisse lassen eine zentrale Generierung der 40 Hz SSR annehmen

Modulations of neural activity in auditory streaming caused by spectral and temporal alternation in subsequent stimuli: a magnetoencephalographic study

Background: The aim of the present study was to identify a specific neuronal correlate underlying the preattentive auditory stream segregation of subsequent sound patterns alternating in spectral or temporal cues. Fifteen participants with normal hearing were presented with series’ of two consecutive ABA auditory tone-triplet sequences, the initial triplets being the Adaptation sequence and the subsequent triplets being the Test sequence. In the first experiment, the frequency separation (delta-f) between A and B tones in the sequences was varied by 2, 4 and 10 semitones. In the second experiment, a constant delta-f of 6 semitones was maintained but the Inter-Stimulus Intervals (ISIs) between A and B tones were varied. Auditory evoked magnetic fields (AEFs) were recorded using magnetoencephalography (MEG). Participants watched a muted video of their choice and ignored the auditory stimuli. In a subsequent behavioral study both MEG experiments were replicated to provide information about the participants’ perceptual state. Results: MEG measurements showed a significant increase in the amplitude of the B-tone related P1 component of the AEFs as delta-f increased. This effect was seen predominantly in the left hemisphere. A significant increase in the amplitude of the N1 component was only obtained for a Test sequence delta-f of 10 semitones with a prior Adaptation sequence of 2 semitones. This effect was more pronounced in the right hemisphere. The additional behavioral data indicated an increased probability of two-stream perception for delta-f = 4 and delta-f = 10 semitones with a preceding Adaptation sequence of 2 semitones. However, neither the neural activity nor the perception of the successive streaming sequences were modulated when the ISIs were alternated. Conclusions: Our MEG experiment demonstrated differences in the behavior of P1 and N1 components during the automatic segregation of sounds when induced by an initial Adaptation sequence. The P1 component appeared enhanced in all Test-conditions and thus demonstrates the preceding context effect, whereas N1 was specifically modulated only by large delta-f Test sequences induced by a preceding small delta-f Adaptation sequence. These results suggest that P1 and N1 components represent at least partially-different systems that underlie the neural representation of auditory streaming

DINAMICA PIEȚEI FORȚEI DE MUNCĂ ÎN BULGARIA

BACKGROUND. Bulgaria, as many countries in the world is experiencing a critical period for the health workforce. The shortage of qualified nurses is one of the biggest obstacles for improving the health-system performance. Lack of strategic planning based on profound market research and elaboration of scientifically based prognosis further deteriorate the current nursing labor market disequilibrium. THE AIM of the study is to explore the main factors influencing the nursing market disequilibrium in Bulgaria and to make an evidence-based forecast of the future needs for nurses in order to suggest relevant workforce development strategies. MATERIAL AND METHODS. The study employs a combination of sociological and statistical methods. The analysis is based on the official statistical data on Bulgarian nursing personnel up to 2012. Primary information is collected through self-administered questionnaires distributed among 337 practicing nurses from April 2007 to December 2012. Data are processed with the packages MS Office Excel 2010 and SPSS v. 13. RESULTS. Results indicate that a decrease in the demand for nursing labour caused large staff layoffs during the first stage of the restructuring period (1990-2000) followed by a severe drop in the number of nurses due to emigration and exodus from the profession. There are also educational and qualification problems along with unattractiveness of the nursing practice due to high workload and low remuneration. With the mean age of 49 severe nursing workforce’s deficit is expected in 10-15 years due to retirement. According to our estimations the deficit of nurses will account for 3162 specialists by 2030. CONCLUSION. The Bulgarian nursing labor market disequilibrium is due to long-term structural imbalances. As the market mechanism is unable to attain equilibrium Bulgarian government should be urgently involved in workforce planning and initiate actions and strategies for producing and retaining the highly qualified nurse professionals in Bulgaria.   Key words: nursing workforce market, Bulgaria, disequilibrium, factors.  CONTEXT. Similar multor state, Bulgaria traversează, de asemenea, o perioadă critică în ceea ce privește piața forței de muncă din sănătate. Lipsa de asistente medicale calificate este unul dintre cele mai mari obstacole pentru îmbunătățirea performanței sistemului de sănătate. Lipsa planificării strategice bazată pe cercetare amănunțită a pieței și lipsa prognozelor și proiecțiilor bazate pe argumente științifice conduc la dezechilibrul existent pe piața muncii asistentelor medicale, existent la momentul actual. SCOPUL studiului este de a explora factorii principali care influențează dezechilibrul de pe piața muncii asistentelor medicale în Bulgaria și de a face prognoze, bazate pe dovezi, ale nevoilor viitoare de asistente medicale, în scopul de a sugera strategii viitoare de dezvoltare a forței de muncă. MATERIAL ȘI METODE. Studiul  de față abordează o combinație de metode sociologice și statistice.  Analiza are la bază date statistice oficiale privind personalul medical din Bulgaria, date disponibile inclusiv pentru anul 2012. Informatiile primare au fost colectate cu ajutorul unor chestionare auto-administrate, distribuite unui număr de 337 asistente medicale practicante, în perioada aprilie 2007 - decembrie 2012. Datele sunt prelucrate cu pachetele de analiză MS Office Excel 2010 și SPSS v. 13. REZULTATE. Rezultatele indică faptul că scăderea cererii pentru asistentele medicale a cauzat  disponibilizările masive din timpul primei etape a perioadei de restructurare 1990-2000, urmată de o scădere severă a numărului de asistente medicale din cauza emigrării și exodul profesional. Există probleme educațiomale și de calificare, alături de lipsa de atractivitate a practicii de asistentă medicală din cauza volumului mare de muncă și a nivelului redus de salarizare. Cu o medie crescută a vârstei asistentelor medicale, de 49 de ani,  un deficit sever este așteptat în următorii 10+15 ani, din cauza fenomenului de pensionare. Conform estimărilor noastre, deficitul de asistente medicale, până în anul 2030, va fi de 3162 de specialiști. CONCLUZII. Dezechilibrul numeric de asistente medicale de pe piața forței de muncă din sănătate este cauza unor dezechilibre structurale pe termen lung. Cum mecanismul piaței nu este în măsură să rezolve acest dezechilibru, guvernul din Bulgaria va trebui urgent să  se implice în planificarea forței de muncă și să inițieze acțiuni și strategii de creare și menținere a asistentelor medicale calificate, în Bulgaria.  Cuvinte cheie: piața forței de muncă, asistente medicale, dezechilibru, factori frenatori, Bulgaria &nbsp

Electrophysiological correlates of selective attention: A lifespan comparison

<p>Abstract</p> <p>Background</p> <p>To study how event-related brain potentials (ERPs) and underlying cortical mechanisms of selective attention change from childhood to old age, we investigated lifespan age differences in ERPs during an auditory oddball task in four age groups including 24 younger children (9–10 years), 28 older children (11–12 years), 31 younger adults (18–25), and 28 older adults (63–74 years). In the Unattend condition, participants were asked to simply listen to the tones. In the Attend condition, participants were asked to count the deviant stimuli. Five primary ERP components (N1, P2, N2, P3 and N3) were extracted for deviant stimuli under Attend conditions for lifespan comparison. Furthermore, Mismatch Negativity (MMN) and Late Discriminative Negativity (LDN) were computed as difference waves between deviant and standard tones, whereas Early and Late Processing Negativity (EPN and LPN) were calculated as difference waves between tones processed under Attend and Unattend conditions. These four secondary ERP-derived measures were taken as indicators for change detection (MMN and LDN) and selective attention (EPN and LPN), respectively. To examine lifespan age differences, the derived difference-wave components for attended (MMN and LDN) and deviant (EPN and LPN) stimuli were specifically compared across the four age groups.</p> <p>Results</p> <p>Both primary and secondary ERP components showed age-related differences in peak amplitude, peak latency, and topological distribution. The P2 amplitude was higher in adults compared to children, whereas N2 showed the opposite effect. P3 peak amplitude was higher in older children and younger adults than in older adults. The amplitudes of N3, LDN, and LPN were higher in older children compared with both of the adult groups. In addition, both P3 and N3 peak latencies were significantly longer in older than in younger adults. Interestingly, in the young adult sample P3 peak amplitude correlated positively and P3 peak latency correlated negatively with performance in the Identical Picture test, a marker measure of fluid intelligence.</p> <p>Conclusion</p> <p>The present findings suggest that patterns of event-related brain potentials are highly malleable within individuals and undergo profound reorganization from childhood to adulthood and old age.</p

A Melodic Contour Repeatedly Experienced by Human Near-Term Fetuses Elicits a Profound Cardiac Reaction One Month after Birth

Human hearing develops progressively during the last trimester of gestation. Near-term fetuses can discriminate acoustic features, such as frequencies and spectra, and process complex auditory streams. Fetal and neonatal studies show that they can remember frequently recurring sounds. However, existing data can only show retention intervals up to several days after birth.Here we show that auditory memories can last at least six weeks. Experimental fetuses were given precisely controlled exposure to a descending piano melody twice daily during the 35(th), 36(th), and 37(th) weeks of gestation. Six weeks later we assessed the cardiac responses of 25 exposed infants and 25 naive control infants, while in quiet sleep, to the descending melody and to an ascending control piano melody. The melodies had precisely inverse contours, but similar spectra, identical duration, tempo and rhythm, thus, almost identical amplitude envelopes. All infants displayed a significant heart rate change. In exposed infants, the descending melody evoked a cardiac deceleration that was twice larger than the decelerations elicited by the ascending melody and by both melodies in control infants.Thus, 3-weeks of prenatal exposure to a specific melodic contour affects infants 'auditory processing' or perception, i.e., impacts the autonomic nervous system at least six weeks later, when infants are 1-month old. Our results extend the retention interval over which a prenatally acquired memory of a specific sound stream can be observed from 3-4 days to six weeks. The long-term memory for the descending melody is interpreted in terms of enduring neurophysiological tuning and its significance for the developmental psychobiology of attention and perception, including early speech perception, is discussed

Good vibrations, bad vibrations: Oscillatory brain activity in the attentional blink

The attentional blink (AB) is a deficit in reporting the second (T2) of two targets (T1, T2) when presented in close temporal succession and within a stream of distractor stimuli. The AB has received a great deal of attention in the past two decades because it allows to study the mechanisms that influence the rate and depth of information processing in various setups and therefore provides an elegant way to study correlates of conscious perception in supra-threshold stimuli. Recently evidence has accumulated suggesting that oscillatory signals play a significant role in temporally coordinating information between brain areas. This review focuses on studies looking into oscillatory brain activity in the AB. The results of these studies indicate that the AB is related to modulations in oscillatory brain activity in the theta, alpha, beta, and gamma frequency bands. These modulations are sometimes restricted to a circumscribed brain area but more frequently include several brain regions. They occur before targets are presented as well as after the presentation of the targets. We will argue that the complexity of the findings supports the idea that the AB is not the result of a processing impairment in one particular process or brain area, but the consequence of a dynamic interplay between several processes and/or parts of a neural network