Global and local complexity of intracranial EEG decreases during NREM sleep

Key to understanding the neuronal basis of consciousness is the characterisation of the neural signatures of changes in level of consciousness during sleep. Here we analysed three measures of dynamical complexity on spontaneous depth electrode recordings from 10 epilepsy patients during wakeful rest and different stages of sleep: (i) Lempel-Ziv complexity, which is derived from how compressible the data are; (ii) amplitude coalition entropy, which measures the variability over time of the set of channels active above a threshold; (iii) synchrony coalition entropy, which measures the variability over time of the set of synchronous channels. When computed across sets of channels that are broadly distributed across multiple brain regions, all 3 measures decreased substantially in all participants during early-night non-rapid eye movement (NREM) sleep. This decrease was partially reversed during late-night NREM sleep, while the measures scored similar to wakeful rest during rapid eye movement (REM) sleep. This global pattern was in almost all cases mirrored at the local level by groups of channels located in a single region. In testing for differences between regions, we found elevated signal complexity in the frontal lobe. These differences could not be attributed solely to changes in spectral power between conditions. Our results provide further evidence that the level of consciousness correlates with neural dynamical complexity

Overcoming cross-cultural group work tensions: mixed student perspectives on the role of social relationships

As universities worldwide rapidly internationalise, higher education classrooms have become unique spaces for collaboration between students from different countries. One common way to encourage collaboration between diverse peers is through group work. However, previous research has highlighted that cross-cultural group work can be challenging and has hinted at potential social tensions. To understand this notion better, we have used robust quantitative tools in this study to select 20 participants from a larger classroom of 860 students to take part in an in-depth qualitative interview about cross-cultural group work experiences. Participant views on social tensions in cross-cultural group work were elicited using a unique mediating artefact method to encourage reflection and in-depth discussion. In our analysis of emergent interview themes, we compared student perspectives on the role of social relationships in group work by their academic performance level. Our findings indicated that all students interviewed desired the opportunity to form social relationships with their group work members, but their motivations for doing so varied widely by academic performance level

Tunable multi-wavelength third-harmonic generation using exposed-core microstructured optical fiber

We demonstrate that exposed-core microstructured optical fibers offer multiple degrees of freedom for tailoring third-harmonic generation through the core diameter, input polarization, and nanofilm deposition. Varying these parameters allows control of the phase-matching position between an infrared pump wavelength and the generated visible wavelengths. In this Letter, we show how increasing the core diameter over previous experiments (2.57 μm compared to 1.85 μm) allows the generation of multiple wavelengths, which can be further controlled by rotating the input pump polarization and the deposition of dielectric nanofilms. This can lead to highly tailorable light sources for applications such as spectroscopy or nonlinear microscopy.Stephen C. Warren-Smith, Kay Schaarschmidt, Mario Chemnitz, Erik P. Schartner, Henrik Schneidewind, Heike Ebendorff-Heidepriem and Markus A. Schmid

High precision pH measurements in biological environments using a portable optical fibre pH sensor

Abstract not availableGeorgina M. Sylvia, Erik P. Schartner, Hanna J. McLennan, Avishkar Saini, Kylie R. Dunning, Malcolm S. Purdey, Andrew D. Abell, Jeremy G. Thompso

Are there islands of awareness?

Ordinary human experience is embedded in a web of causal relations that link the brain to the body and the wider environment. However, there might be conditions in which brain activity supports consciousness even when that activity is fully causally isolated from the body and its environment. Such cases would involve what we call ‘islands of awareness’: conscious states that are neither shaped by sensory input nor able to be expressed by motor output. This paper considers conditions in which such islands might occur, including ex cranio brains, hemispherotomy, and in cerebral organoids. We examine possible methods for 2 detecting islands of awareness, and consider their implications for ethics and for the nature of consciousness

Complexity of multi-dimensional spontaneous EEG decreases during propofol induced general anaesthesia

Emerging neural theories of consciousness suggest a correlation between a specific type of neural dynamical complexity and the level of consciousness: When awake and aware, causal interactions between brain regions are both integrated (all regions are to a certain extent connected) and differentiated (there is inhomogeneity and variety in the interactions). In support of this, recent work by Casali et al (2013) has shown that Lempel-Ziv complexity correlates strongly with conscious level, when computed on the EEG response to transcranial magnetic stimulation. Here we investigated complexity of spontaneous high-density EEG data during propofol-induced general anaesthesia. We consider three distinct measures: (i) Lempel-Ziv complexity, which is derived from how compressible the data are; (ii) amplitude coalition entropy, which measures the variability in the constitution of the set of active channels; and (iii) the novel synchrony coalition entropy (SCE), which measures the variability in the constitution of the set of synchronous channels. After some simulations on Kuramoto oscillator models which demonstrate that these measures capture distinct ‘flavours’ of complexity, we show that there is a robustly measurable decrease in the complexity of spontaneous EEG during general anaesthesia

Taming the light in microstructured optical fibers for sensing

In this review, we examine recent developments in the field of chemical and biological sensing utilizing suspended-core, exposed-core, and hollow-core microstructured optical fibers. Depending on the intended application, a host of sensing modalities have been utilized including labelled fluorescence techniques, and label-free methods such as surface plasmon resonance, fiber Bragg gratings, and Raman scattering. The use of various functionalization techniques adds specificity to both chemical ions and biological molecules. The results shown here highlight some of the important benefits that arise with the use of microstructured optical fibers compared to traditional techniques, including small sample volumes, high sensitivity, and multiplexing.Erik P. Schartner, Georgios Tsiminis, Alexandre François, Roman Kostecki, Stephen C. Warren-Smith, Linh Viet Nguyen, Sabrina Heng, Tess Reynolds, Elizaveta Klantsataya, Kris J. Rowland, Andrew D. Abell, Heike Ebendorff-Heidepriem, Tanya M. Monr

Perspective: biomedical sensing and imaging with optical fibers - innovation through convergence of science disciplines

The probing of physiological processes in living organisms is a grand challenge that requires bespoke analytical tools. Optical fiber probes offer a minimally invasive approach to report physiological signals from specific locations inside the body. This perspective article discusses a wide range of such fiber probes developed at the Australian Research Council Centre of Excellence for Nanoscale BioPhotonics. Our fiber platforms use a range of sensing modalities, including embedded nanodiamonds for magnetometry, interferometric fiber cavities for refractive index sensing, and tailored metal coatings for surface plasmon resonance sensing. Other fiber probes exploit molecularly sensitive Raman scattering or fluorescence where optical fibers have been combined with chemical and immunosensors. Fiber imaging probes based on interferometry and computational imaging are also discussed as emerging in vivo diagnostic devices. We provide examples to illustrate how the convergence of multiple scientific disciplines generates opportunities for the fiber probes to address key challenges in real-time in vivo diagnostics. These future fiber probes will enable the asking and answering of scientific questions that were never possible before.Jiawen Li ... Heike Ebendorff-Heidepriem ... Mark R. Hutchinson ... Roman Kostecki ... Erik P. Schartner ... Georgios Tsiminis ... Stephen C. Warren-Smith ... et al

Partitioning variability in animal behavioral videos using semi-supervised variational autoencoders

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