Toolkit for Oscillatory Real-time Tracking and Estimation (TORTE)

Closing the loop between brain activity and behavior is one of the most active areas of development in neuroscience. There is particular interest in developing closed-loop control of neural oscillations. Many studies report correlations between oscillations and functional processes. Oscillation-informed closed-loop experiments might determine whether these relationships are causal and would provide important mechanistic insights which may lead to new therapeutic tools. These closed-loop perturbations require accurate estimates of oscillatory phase and amplitude, which are challenging to compute in real time. We developed an easy to implement, fast and accurate Toolkit for Oscillatory Real-time Tracking and Estimation (TORTE). TORTE operates with the open-source Open Ephys GUI (OEGUI) system, making it immediately compatible with a wide range of acquisition systems and experimental preparations. TORTE efficiently extracts oscillatory phase and amplitude from a target signal and includes a variety of options to trigger closed-loop perturbations. Implementing these tools into existing experiments is easy and adds minimal latency to existing protocols. Most labs use in-house lab-specific approaches, limiting replication and extension of their experiments by other groups. Accuracy of the extracted analytic signal and accuracy of oscillation-informed perturbations with TORTE match presented results by these groups. However, TORTE provides access to these tools in a flexible, easy to use toolkit without requiring proprietary software. We hope that the availability of a high-quality, open-source, and broadly applicable toolkit will increase the number of labs able to perform oscillatory closed-loop experiments, and will improve the replicability of protocols and data across labs.

Numerical Analysis of a Water-Cooled Condenser at Startup Conditions for Refrigeration Applications Supported with Experiments

Refrigeration for commercial purposes is one of the industrial sectors with the largest energy consumption in the global market. Therefore, research and development of more efficient components such as compressors, condensers, and refrigerants continue to render promising results in terms of GWP and operational costs. However, Due to the urgency typically found in industry to develop prototypes, finding scalable solutions can be challenging. Arguably, this is the case for condenser and evaporators that are designed and assembled under the assumption that refrigeration systems operate at steady condition, where in real circumstances such systems operate under transients based on ambient temperatures or unfavorable startup conditions. The aim of this study is to characterize the thermal and fluid dynamics behavior of refrigerant R404a in a water-cooled condenser at startup conditions. The boundary conditions to solve the CFD simulations are taken from experimental values and set as user defined functions in a commercial software. The results displayed the time dependent oscillatory phase-transition details of the refrigerant throughout the domain.

Test-retest reliability of neural entrainment in the human auditory system

Auditory stimuli are often rhythmic in nature. Brain activity synchronizes with auditory rhythms via neural entrainment, and entrainment seems to be beneficial for auditory perception. However, it is not clear to what extent neural entrainment in the auditory system is reliable over time – a necessary prerequisite for targeted intervention. The current study aimed to establish the reliability of neural entrainment over time and to predict individual differences in auditory perception from associated neural activity. Across two different sessions, human listeners detected silent gaps presented at different phase locations of a 2-Hz frequency modulated (FM) noise while EEG activity was recorded. As expected, neural activity was entrained by the 2-Hz FM noise. Moreover, gap detection was sinusoidally modulated by the phase of the 2-Hz FM into which the gap fell. Critically, both the strength of neural entrainment as well as the modulation of performance by the stimulus rhythm were highly reliable over sessions. Moreover, gap detection was predictable from pre-gap neural 2-Hz phase. Going beyond previous work, we found that stimulus-driven behavioral modulation was better predicted by the interaction between delta and alpha phase than by delta or alpha phase alone, both within and across sessions. Taken together, our results demonstrate that neural entrainment in the auditory system and the resulting behavioral modulation are reliable over time. In addition, both entrained delta and non-entrained alpha oscillatory phase contribute to near-threshold stimulus perception.

Quantum fluctuations and cosmological particle creation from oscillating massive scalar field in two-mode quantum optical states

In this paper, by the use of entangled and nonentangled coherent and squeezed state formalism of two-mode nonclassical states, we studied the chaotic inflationary model of a massive scalar field with quadratic potential in the semiclassical gravity, derived from canonical quantum gravity. It was found that the semiclassical quantum gravity leads to the same power-law expansion of the universe as that of the matter-dominated era [Formula: see text] in an oscillatory phase of the scalar field in all the nonclassical quantum states considered. The coherently oscillating scalar field in the expanding universe suffers from the phenomenon of particle creation which restricts the duration of stable coherent oscillations of the scalar field dependent on the parameters of the states considered and affect in a certain way the abundant particle production owing to the parametric resonance of bosonic fields coupled to this coherently oscillating scalar field.

Time-Series Prediction of the Oscillatory Phase of EEG Signals Using the Least Mean Square Algorithm-Based AR Model

Neural oscillations are vital for the functioning of a central nervous system because they assist in brain communication across a huge network of neurons. Alpha frequency oscillations are believed to depict idling or inhibition of task-irrelevant cortical activities. However, recent studies on alpha oscillations (particularly alpha phase) hypothesize that they have an active and direct role in the mechanisms of attention and working memory. To understand the role of alpha oscillations in several cognitive processes, accurate estimations of phase, amplitude, and frequency are required. Herein, we propose an approach for time-series forward prediction by comparing an autoregressive (AR) model and an adaptive method (least mean square (LMS)-based AR model). This study tested both methods for two prediction lengths of data. Our results indicate that for shorter data segments (prediction of 128 ms), the AR model outperforms the LMS-based AR model, while for longer prediction lengths (256 ms), the LMS- based AR model surpasses the AR model. LMS with low computational cost can aid in electroencephalography (EEG) phase prediction (alpha oscillations) in basic research to reveal the functional role of the oscillatory phase as well as for applications for brain-computer interfaces.

Oscillatory entrainment mechanisms and anticipatory predictive processes in Autism Spectrum Disorder (ASD)

ABSTRACTAnticipating near-future events is fundamental to adaptive behavior, whereby neural processing of predictable stimuli is significantly facilitated relative to non-predictable inputs. Neural oscillations appear to be a key anticipatory mechanism by which processing of upcoming stimuli is modified, and they often entrain to rhythmic environmental sequences. Clinical and anecdotal observations have led to the hypothesis that people with Autism Spectrum Disorder (ASD) may have deficits in generating predictions in daily life, and as such, a candidate neural mechanism may be failure to adequately entrain neural activity to repetitive environmental patterns. Here, we tested this hypothesis by interrogating rhythmic entrainment both behaviorally and electrophysiologically. We recorded high-density electroencephalography in children with ASD (n=31) and Typically Developing (TD) age- and IQ-matched controls (n=20), while they reacted to an auditory target as quickly as possible. This auditory event was either preceded by predictive rhythmic visual cues, or not. Results showed that while both groups presented highly comparable evoked responses to the visual stimuli, children with ASD showed reduced neural entrainment to the rhythmic visual cues, and altered anticipation of the occurrence of these stimuli. Further, in both groups, neuro-oscillatory phase coherence correlated with behavior. These results describe neural processes that may underlie impaired event anticipation in children with ASD, and support the notion that their perception of events is driven more by instantaneous sensory inputs and less by their temporal predictability.

Spike timing in the attention network predicts behavioral outcome prior to target selection

ABSTRACTThere has been little evidence linking changes in spiking activity that occur prior to a spatially predictable target (i.e., prior to target selection) to behavioral outcomes, despite such preparatory changes being widely assumed to enhance the sensitivity of sensory processing. We simultaneously recorded from frontal and parietal nodes of the attention network, while macaques performed a spatial-cueing task. When anticipating a spatially predictable target, different patterns of coupling between spike timing and oscillatory phase in local field potentials—but not changes in spike rate—were predictive of different behavioral outcomes. These behaviorally relevant differences in local and between-region synchronization occurred among specific cell types that were defined based on their sensory and motor properties, providing insight into the mechanisms underlying enhanced sensory processing prior to target selection. We propose that these changes in neural synchronization reflect differential, anticipatory engagement of the network nodes and functional units that shape attention-related sampling.

Oscillating inflaton power-law cosmology in two-mode quantum optical states

In this paper, we study the semiclassical evolution of a “coherently oscillating massive scalar field”. This field is nominally linked to the spatially levelled Friedmann–Robertson–Walker (FRW) metric. By use of two-mode quantum optical states formalism, we evaluated the power-law cosmology with scale factor as a power function of cosmic time. In the oscillatory phase of scalar field, it was found that, in all the four different combinations of quantum states, quantum scalar field obeying the time-dependent Schrödinger equation leads to the power-law expansion, in good agreement with that of the matter-dominated era. However, in the semiclassical theory of gravity in contrary to the classical description of gravity, we obtained two behavioral solutions corresponding to two different pattern evolution of the scale factor. This behavioral pattern evolution of scale factor of the universe has an important quantum implication associated with it.

Quantum fluctuations and particle production in the oscillatory phase of a thermal inflaton in a FRW universe

By the use of coherent and squeezed thermal states formalism, we analyzed the phenomena of particle creation when coherently oscillating a homogeneous scalar field (Inflaton) in semi-classical gravity. We also obtained an estimated solution for the semi-classical Einstein equation in non-classical thermal states formalism perturbatively, which is similar to the power-law expansion of classical Einstein equation. This solution, apart from a particular condition, shows oscillatory behavior in nature. We also analyzed a coherently oscillating homogeneous scalar field, in a thermal vacuum, coherent thermal, squeezed thermal vacuum and coherent squeezed thermal states, suffering from particle creation, and created particles are showing oscillatory behavior. Particle production can be raised due to thermal and quantum effects. We also studied quantum fluctuations of a homogeneous scalar field in the above-mentioned non-classical thermal states.