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Induced oscillatory brain responses under virtual reality conditions in the context of repetition priming
In the human electroencephalogram (EEG), induced oscillatory responses in various frequency bands are regarded as valuable indices to examine the neural mechanisms underlying human memory. While the advent of virtual reality (VR) drives the investigation of mnemonic processing under more lifelike settings, the joint application of VR and EEG methods is still in its infancy (e.g., due to technical limitations impeding the signal acquisition). The objective of the present EEG study was twofold. First, we examined whether the investigation of induced oscillations under VR conditions yields equivalent results compared to standard paradigms. Second, we aimed at obtaining further insights into basic memory-related brain mechanisms in VR. To these ends, we relied on a standard implicit memory design, namely repetition priming, for which the to-be-expected effects are well-documented for conventional studies. Congruently, we replicated a suppression of the evoked potential after stimulus onset. Regarding the induced responses, we observed a modulation of induced alphaband in response to a repeated stimulus. Importantly, our results revealed a repetition-related suppression of the high-frequency induced gammaband response (>30 Hz), indicating the sharpening of a cortical object representation fostering behavioral priming effects. Noteworthy, the analysis of the induced gammaband responses required a number of measures to minimize the influence of external and internal sources of artefacts (i.e., the electrical shielding of the technical equipment and the control for miniature eye movements). In conclusion, joint VR–EEG studies with a particular focus on induced oscillatory responses offer a promising advanced understanding of mnemonic processing under lifelike conditions.
Journal Article
Repetition, recurrence, returns : how cultural renewal works
\"Repetition is constitutive of human life. Unlike simple recall, repetition is permeated by the past and the present and is oriented toward the future. This book investigates the significance of different forms of repetition in literature, culture, and society through studies of the function and importance of an array of repetitive phenomenon.\" -- Provided by publisher.
BOOK
High repetition rate Petawatt lasers
Petawatt lasers are now available in a number of facilities around the world and are becoming a very useful tool in physics and engineering. Some of such lasers are able -or will be able soon- to fire at high repetition rates (one shot per second or more). Experiments at such repetition rates have certain peculiarities that are to be briefly exposed here, based on the author’s experience with the Salamanca VEGA-3 laser. VEGA-3 is a 30 fs PW laser, firing one shot per second.
Journal Article
Synchronized multi-wavelength soliton fiber laser via intracavity group delay modulation
Locking of longitudinal modes in laser cavities is the common path to generate ultrashort pulses. In traditional multi-wavelength mode-locked lasers, the group velocities rely on lasing wavelengths due to the chromatic dispersion, yielding multiple trains of independently evolved pulses. Here, we show that mode-locked solitons at different wavelengths can be synchronized inside the cavity by engineering the intracavity group delay with a programmable pulse shaper. Frequency-resolved measurements fully retrieve the fine temporal structure of pulses, validating the direct generation of synchronized ultrafast lasers from two to five wavelengths with sub-pulse repetition-rate up to ~1.26 THz. Simulation results well reproduce and interpret the key experimental phenomena, and indicate that the saturable absorption effect automatically synchronize multi-wavelength solitons in despite of the small residual group delay difference. These results demonstrate an effective approach to create synchronized complex-structure solitons, and offer an effective platform to study the evolution dynamics of nonlinear wavepackets.
The coherence degradation of pulses synchronized to optical cavities is an issue for ultrahigh-repetition-rate lasing. Here the authors demonstrate synchronized multi-wavelength mode-locked soliton fiber lasers generating ultrafast outputs from two to five wavelengths with a high sub-pulse repetition rate.
Journal Article
Over and over : exploring repetition in popular music
From the Tin Pan Alley 32-bar form, through the cyclical forms of modal jazz, to the more recent accumulation of digital layers, beats, and breaks in Electronic Dance Music, repetition as both an aesthetic disposition and a formal property has stimulated a diverse range of genres and techniques. From the angles of musicology, psychology, sociology, and science and technology, Over and Over reassesses the complexity connected to notions of repetition in a variety of musical genres. The first edited volume on repetition in 20th- and 21st-century popular music, Over and Over explores the wide-ranging forms and use of repetition - from large repetitive structures to micro repetitions - in relation to both specific and large-scale issues and contexts. The book brings together a selection of original texts by leading authors in a field that is, as yet, little explored. Aimed at both specialists and neophytes, it sheds important new light on one of the fundamental phenomena of music of our times.
Book
Glutamatergic correlates of gamma-band oscillatory activity during cognition: A concurrent ER-MRS and EEG study
Frequency specific synchronisation of neuronal firing within the gamma-band (30–70Hz) appears to be a fundamental correlate of both basic sensory and higher cognitive processing. In-vitro studies suggest that the neurochemical basis of gamma-band oscillatory activity is based on interactions between excitatory (i.e. glutamate) and inhibitory (i.e. GABA) neurotransmitter concentrations. However, the nature of the relationship between excitatory neurotransmitter concentration and changes in gamma band activity in humans remains undetermined. Here, we examine the links between dynamic glutamate concentration and the formation of functional gamma-band oscillatory networks. Using concurrently acquired event-related magnetic resonance spectroscopy and electroencephalography, during a repetition-priming paradigm, we demonstrate an interaction between stimulus type (object vs. abstract pictures) and repetition in evoked gamma-band oscillatory activity, and find that glutamate levels within the lateral occipital cortex, differ in response to these distinct stimulus categories. Importantly, we show that dynamic glutamate levels are related to the amplitude of stimulus evoked gamma-band (but not to beta, alpha or theta or ERP) activity. These results highlight the specific connection between excitatory neurotransmitter concentration and amplitude of oscillatory response, providing a novel insight into the relationship between the neurochemical and neurophysiological processes underlying cognition.
•Evoked gamma-band activity changes in response to both object and abstract stimuli.•Glutamate levels in the LOC differ in response to distinct visual stimuli.•Glutamate levels correlate with concurrently measured gamma-band oscillatory power.•ER-MRS can quantify neurochemical concentration changes related to the EEG signal.
Journal Article
What do test scores miss?
Teachers affect a variety of student outcomes through their influence on both cognitive and noncognitive skill. I proxy for students’ noncognitive skill using non–test score behaviors. These behaviors include absences, suspensions, course grades, and grade repetition in ninth grade. Teacher effects on test scores and those on behaviors are weakly correlated. Teacher effects on behaviors predict larger impacts on high school completion and other longer-run outcomes than their effects on test scores. Relative to using only test score measures, using effects on both test score and noncognitive measures more than doubles the variance of predictable teacher impacts on longer-run outcomes.
Journal Article