RNA recoding in cephalopods tailors microtubule motor protein function.

RNA editing is a widespread epigenetic process that can alter the amino acid sequence of proteins, termed "recoding." In cephalopods, most transcripts are recoded, and recoding is hypothesized to be an adaptive strategy to generate phenotypic plasticity. However, how animals use RNA recoding dynamically is largely unexplored. We investigated the function of cephalopod RNA recoding in the microtubule motor proteins kinesin and dynein. We found that squid rapidly employ RNA recoding in response to changes in ocean temperature, and kinesin variants generated in cold seawater displayed enhanced motile properties in single-molecule experiments conducted in the cold. We also identified tissue-specific recoded squid kinesin variants that displayed distinct motile properties. Finally, we showed that cephalopod recoding sites can guide the discovery of functional substitutions in non-cephalopod kinesin and dynein. Thus, RNA recoding is a dynamic mechanism that generates phenotypic plasticity in cephalopods and can inform the characterization of conserved non-cephalopod proteins.

In Situ Local Imaging of Ferromagnetism and Superconductivity in RbEuFe4As4.

The coexistence of superconductivity and ferromagnetism is an intrinsically interesting research focus in condensed matter physics, but the study is limited by low superconducting (Tc) and magnetic (Tm) transition temperatures in related materials. Here, we used a scanning superconducting quantum interference device to image the in situ diamagnetic and ferromagnetic responses of RbEuFe4As4 with high Tc and Tm. We observed significant suppression of the superfluid density in the vicinity of the magnetic phase transition, signifying fluctuation-enhanced magnetic scatterings between Eu spins and Fe 3d conduction electrons. Intriguingly, we observed multiple ferromagnetic domains that should be absent in an ideal magnetic helical phase. The formation of these domains demonstrates a weak c-axis ferromagnetic component probably arising from the Eu spin-canting effect, indicative of possible superconductivity-driven domain Meissner and domain vortex-antivortex phases, as revealed in EuFe2(As0.79P0.21)2. Our observations highlight that RbEuFe4As4 is a unique system that includes multiple interplay channels between superconductivity and ferromagnetism.

Squid male alternative reproductive tactics are determined by birth date.

Alternative reproductive tactics (ARTs) are discontinuous phenotypes associated with reproduction, observed in males of many species. Typically, large males adopt a tactic of competing with rivals for mating, while small males adopt a tactic of stealing fertilization opportunities from the large males. The 'birth date hypothesis', proposing that the date of birth influences the determination of each male's reproductive tactic, has been tested only in teleost fish to date. Here, the birth date hypothesis was tested in ARTs of Japanese spear squid Heterololigo bleekeri (consort/sneaker) by analysing statolith growth increments. The birth date significantly differed between consorts (early-hatched) and sneakers (late-hatched). However, no differences were detected in growth history up to 100 days from hatching. Most immature males caught during the reproductive season were larger than sneakers, and their hatch date was similar to that of consorts, suggesting that these immature males had already been following a life-history pathway as a consort. These results indicate that ARTs of H. bleekeri are determined based on their hatch date in early life. This study firstly suggests that the birth date hypothesis applies to aquatic invertebrates, suggesting that the mechanism by which birth date determines the individual phenotype is a phenomenon more common than previously believed.

Corrected and republished from: "Vibrio fischeri Possesses Xds and Dns Nucleases That Differentially Influence Phosphate Scavenging, Aggregation, Competence, and Symbiotic Colonization of Squid".

Cells of Vibrio fischeri colonize the light organ of Euprymna scolopes, providing the squid bioluminescence in exchange for nutrients and protection. The bacteria encounter DNA-rich mucus throughout their transition to a symbiotic lifestyle, leading us to hypothesize a role for nuclease activity in the colonization process. In support of this, we detected abundant extracellular nuclease activity in growing cells of V. fischeri. To discover the gene(s) responsible for this activity, we screened a V. fischeri transposon mutant library for nuclease-deficient strains. Interestingly, only one strain, whose transposon insertion mapped to nuclease gene VF_1451, showed a complete loss of nuclease activity in our screens. A database search revealed that VF_1451 is homologous to the nuclease-encoding gene xds in Vibrio cholerae. However, V. fischeri strains lacking xds eventually revealed slight nuclease activity on plates upon prolonged incubation. This led us to hypothesize that a second secreted nuclease, identified through a database search as VF_0437, a homolog of V. cholerae dns, might be responsible for the residual nuclease activity. Here, we show that Xds and/or Dns are involved in essential aspects of V. fischeri biology, including natural transformation, aggregation, and phosphate scavenging. Furthermore, strains lacking either nuclease were outcompeted by the wild type for squid colonization. Understanding the specific role of nuclease activity in the squid colonization process represents an intriguing area of future research.IMPORTANCEFrom soil and water to host-associated secretions such as mucus, environments that bacteria inhabit are awash in DNA. Extracellular DNA (eDNA) is a nutritious resource that microbes dedicate significant energy to exploit. Calcium binds eDNA to promote cell-cell aggregation and horizontal gene transfer. eDNA hydrolysis impacts the construction of and dispersal from biofilms. Strategies in which pathogens use nucleases to avoid phagocytosis or disseminate by degrading host secretions are well-documented; significantly less is known about nucleases in mutualistic associations. This study describes the role of nucleases in the mutualism between Vibrio fischeri and its squid host Euprymna scolopes. We find that nuclease activity is an important determinant of colonization in V. fischeri, broadening our understanding of how microbes establish and maintain beneficial associations.

Stem-Cell-Regenerative and Protective Effects of Squid (Symplectoteuthis oualaniensis) Skin Collagen Peptides against H2O2-Induced Fibroblast Injury.

Recently, there has been a growing interest in collagen peptides derived from marine sources for their notable ability to protect skin cells against apoptosis induced by oxidants. Therefore, the current study aimed to investigate the fundamental properties of collagen peptides, including their physicochemical, thermal, structural, stem-cell-regenerative, and skin-cell-protective effects, in comparison to commercial collagen peptides. The acid-soluble (ASC) and pepsin-soluble (PSC) collagens exhibited three distinct bands on SDS-PAGE, namely α (α1 and α2), ß, and γ chains, confirming a type I pattern. The thermal profiles obtained from TG and DSC analyses confirmed the denaturation of PSC and ASC at temperatures ranging from 51.94 to 56.4 °C and from 52.07 to 56.53 °C, respectively. The purified collagen peptides were analyzed using SDS-PAGE and MALDI-TOF mass spectrometry, revealing a mass range of 900-15,000 Da. Furthermore, the de novo peptide sequence analysis confirmed the presence of the Gly-X-Y repeating sequence in collagen peptides. Collagen peptide treatments significantly enhanced HFF-1 cell proliferation and migration compared to the control group. ELISA results confirmed the potential interactions between collagen peptides and HFF-1 cells through α2ß1, α10ß1, and α11ß1 integrin receptors. Notably, collagen peptide treatment effectively restored the proliferation of HFF-1 cells damaged by H2O2. Consequently, the advantageous characteristics of squid skin collagen peptides highlight their promising role in regenerative medicine.

Protein Hydrolysis as a Way to Valorise Squid-Processing Byproducts: Obtaining and Identification of ACE, DPP-IV and PEP Inhibitory Peptides.

The industrial processing of Argentine shortfin squid to obtain rings generates a significant amount of protein-rich waste, including the skin, which is rich in collagen and attached myofibrillar proteins. This waste is generally discarded. In this study, skin was used as a source of proteins that were hydrolysed using Trypsin, Esperase® or Alcalase®, which released peptides with antioxidant potential and, in particular, antihypertensive (ACE inhibition), hypoglycemic (DPP-IV inhibition) and/or nootropic (PEP inhibition) potential. Among the three enzymes tested, Esperase® and Alcalase produced hydrolysates with potent ACE-, DPP-IV- and PEP-inhibiting properties. These hydrolysates underwent chromatography fractionation, and the composition of the most bioactive fractions was analysed using HPLC-MS-MS. The fractions with the highest bioactivity exhibited very low IC50 values (16 and 66 µg/mL for ACE inhibition, 97 µg/mL for DPP-IV inhibition and 55 µg/mL for PEP inhibition) and were mainly derived from the hydrolysate obtained using Esperase®. The presence of Leu at the C-terminal appeared to be crucial for the ACE inhibitory activity of these fractions. The DPP-IV inhibitory activity of peptides seemed to be determined by the presence of Pro or Ala in the second position from the N-terminus, and Gly and/or Pro in the last C-terminal positions. Similarly, the presence of Pro in the peptides present in the best PEP inhibitory fraction seemed to be important in the inhibitory effect. These results demonstrate that the skin of the Argentine shortfin squid is a valuable source of bioactive peptides, suitable for incorporation into human nutrition as nutraceuticals and food supplements.

Superconducting Quantum Magnetometer Based on Flux Focusing Effect for High-Sensitivity Applications.

A superconducting quantum magnetometer for high-sensitivity applications has been developed by exploiting the flux focusing of the superconducting loop. Unlike conventional dc SQUID magnetometers that use a superconducting flux transformer or a multiloop design, in this case, a very simple design has been employed. It consists of a bare dc SQUID with a large washer-shaped superconducting ring in order to guarantee a magnetic field sensitivity BΦ less than one nT/Φ0. The degradation of the characteristics of the device due to an inevitable high value of the inductance parameter ßL was successfully compensated by damping the inductance of the dc SQUID. The size of the magnetometer, coinciding with that of the washer, is 5 × 5 mm2 and the spectral density of the magnetic field noise is 8 fT/√Hz with a low frequency noise knee of two Hz. The excellent performance of this simple magnetometer makes it usable for all high-sensitivity applications including magnetoencephalography.

Chip-Integrated Vortex Manipulation.

The positions of Abrikosov vortices have long been considered as means to encode classical information. Although it is possible to move individual vortices using local probes, the challenge of scalable on-chip vortex-control remains outstanding, especially when considering the demands of controlling multiple vortices. Realization of vortex logic requires means to shuttle vortices reliably between engineered pinning potentials, while concomitantly keeping all other vortices fixed. We demonstrate such capabilities using Nb loops patterned below a NbSe2 layer. SQUID-on-Tip (SOT) microscopy reveals that the loops localize vortices in designated sites to a precision better than 100 nm; they realize "push" and "pull" operations of vortices as far as 3 µm. Successive application of such operations shuttles a vortex between adjacent loops. Our results may be used as means to integrate vortices in future quantum circuitry. Strikingly, we demonstrate a winding operation, paving the way for future topological quantum computing and simulations.

High Magnetic Field Stability in a Planar Graphene-NbSe2 SQUID.

Thin NbSe2 retains superconductivity at a high in-plane magnetic field up to 30 T. In this work we construct a novel atomically thin, all van der Waals SQUID, in which current flows between NbSe2 contacts through two parallel graphene weak links. The 2D planar SQUID remains uniquely stable at high in-plane field, which enables tracing critical current interference patterns as a function of the field up to 4.5 T. From these we extract the evolution of the current distribution up to high fields, demonstrating sub-nanometer sensitivity to deviation of current flow from a perfect atomic plane and observing a field-driven transition in which supercurrent redistributes to a narrow channel. We further suggest a new application of the asymmetric SQUID geometry to directly probe the current density in the absence of phase information.

Limitations of the Current-Phase Relation Measurements by an Asymmetric dc-SQUID.

Exotic quantum transport phenomena established in Josephson junctions (JJs) are reflected by a nonsinusoidal current-phase relation (CPR). The solidified approach to measuring the CPR is via an asymmetric dc-SQUID with a reference JJ that has a high critical current. We probed this method by measuring CPRs of hybrid JJs based on the 3D topological insulator (TI) Bi2Te2Se with a nanobridge acting as a reference JJ. We captured both highly skewed and sinusoidal critical current oscillations within single devices which contradict the uniqueness of the CPR. This implies that the widely used method provides inaccurate CPR measurement and leads to misinterpretation. It was shown that the accuracy of the CPR measurement is mediated by the asymmetry in derivatives of the CPRs but not in critical currents, as was previously thought. Finally, we provided considerations for an accurate CPR measurement via the most commonly used reference JJs.

Current-Phase Relation of a WTe2 Josephson Junction.

When a topological insulator is incorporated into a Josephson junction, the system is predicted to reveal the fractional Josephson effect with a 4π-periodic current-phase relation. Here, we report the measurement of a 4π-periodic switching current through an asymmetric SQUID, formed by the higher-order topological insulator WTe2. Contrary to the established opinion, we show that a high asymmetry in critical current and negligible loop inductance are not sufficient by themselves to reliably measure the current-phase relation. Instead, we find that our measurement is heavily influenced by additional inductances originating from the self-formed PdTex inside the junction. We therefore develop a method to numerically recover the current-phase relation of the system and find the 1.5 µm long junction to be best described in the short ballistic limit. Our results highlight the complexity of subtle inductance effects that can give rise to misleading topological signatures in transport measurements.

Spin Frustration in Organic Radicals.

Spin frustration, which results from geometric frustration and a systematical inability to satisfy all antiferromagnetic (AF) interactions between unpaired spins simultaneously, is under the spotlight for its importance in physics and materials science. Spin frustration is treated as the structural basis of quantum spin liquids (QSLs). Featuring flexible chemical structures, organic radical species exhibit great potential in building spin-frustrated molecules and lattices. So far, the reported examples of spin-frustrated organic radical compounds include triradicals, tetrathiafulvalene (TTF) radicals and derivatives, [Pd(dmit)2 ] compounds (dmit=1,3-dithiol-2-thione-4,5-dithiolate), nitronyl nitroxides, fullerenes, polycyclic aromatic hydrocarbons (PAHs), and other heterocyclic compounds where the spin frustration is generated intra- or intermolecularly. In this Minireview, we provide a brief summary of the reported radical compounds that possess spin frustration. The related data, including magnetic exchange coupling parameters, spin models, frustration parameters, and crystal lattices, are summarized and discussed.

Validation of liver quantitative susceptibility mapping across imaging parameters at 1.5 T and 3.0 T using SQUID susceptometry as reference.

PURPOSE: To validate QSM-based biomagnetic liver susceptometry (BLS) to measure liver iron overload at 1.5 T and 3.0 T using superconducting quantum interference devices (SQUID)-based BLS as reference. METHODS: Subjects with known or suspected iron overload were recruited for QSM-BLS at 1.5 T and 3.0 T using eight different protocols. SQUID-BLS was also obtained in each subject to provide susceptibility reference. A recent QSM method based on data-adaptive regularization was used to obtain susceptibility and R 2 * $$ {\mathrm{R}}_2^{\ast } $$ maps. Measurements of susceptibility and R 2 * $$ {\mathrm{R}}_2^{\ast } $$ were obtained in the right liver lobe. Linear mixed-effects analysis was used to estimate the contribution of specific acquisition parameters to QSM-BLS. Linear regression and Bland-Altman analyses were used to assess the relationship between QSM-BLS and SQUID-BLS/ R 2 * $$ {\mathrm{R}}_2^{\ast } $$ . RESULTS: Susceptibility maps showed high subjective quality for each acquisition protocol across different iron levels. High linear correlation was observed between QSM-BLS and SQUID-BLS at 1.5 T (r2 range, [0.82, 0.84]) and 3.0 T (r2 range, [0.77, 0.85]) across different acquisition protocols. QSM-BLS and R 2 * $$ {\mathrm{R}}_2^{\ast } $$ were highly correlated at both field strengths (r2 range at 1.5 T, [0.94, 0.99]; 3.0 T, [0.93, 0.99]). High correlation (r2  = 0.99) between 1.5 T and 3.0 T QSM-BLS, with narrow reproducibility coefficients (range, [0.13, 0.21] ppm) were observed for each protocol. CONCLUSION: This work evaluated the feasibility and performance of liver QSM-BLS across iron levels and acquisition protocols at 1.5 T and 3.0 T. High correlation and reproducibility were observed between QSM-BLS and SQUID-BLS across protocols and field strengths. In summary, QSM-BLS may enable reliable and reproducible quantification of liver iron concentration.

One size does not fit all: diversity of length-force properties of obliquely striated muscles.

Obliquely striated muscles occur in 17+ phyla, likely evolving repeatedly, yet the implications of oblique striation for muscle function are unknown. Contrary to the belief that oblique striation allows high force output over extraordinary length ranges (i.e. superelongation), recent work suggests diversity in operating length ranges and length-force relationships. We hypothesize oblique striation evolved to increase length-force relationship flexibility. We predict that superelongation is not a general characteristic of obliquely striated muscles and instead that length-force relationships vary with operating length range. To test these predictions, we measured length-force relationships of five obliquely striated muscles from inshore longfin squid, Doryteuthis pealeii: tentacle, funnel retractor and head retractor longitudinal fibers, and arm and fin transverse fibers. Consistent with superelongation, the tentacle length-force relationship had a long descending limb, whereas all others exhibited limited descending limbs. The ascending limb at 0.6P0 was significantly broader (P<0.001) for the tentacle length-force relationship (0.43±0.04L0; where L0 is the preparation length that produced peak isometric stress, P0) than for the arm (0.29±0.03L0), head retractor (0.24±0.06L0), fin (0.20±0.04L0) and funnel retractor (0.27±0.03L0). The fin's narrow ascending limb differed significantly from those of the arm (P=0.004) and funnel retractor (P=0.012). We further characterized the tentacle preparation's maximum isometric stress (315±78 kPa), maximum unloaded shortening velocity (2.97±0.55L0 s-1) and ultrastructural traits (compared with the arm), which may explain its broader length-force relationship. Comparison of obliquely striated muscles across taxa revealed length-force relationship diversity, with only two species exhibiting superelongation.

Lolliginicoccus levis gen. nov., sp. nov., a novel bacterium isolated from the brain of the Chiroteuthis picteti squid, and reclassification of two Hoyosella species as Lolliginicoccus suaedae comb. nov. and Lolliginicoccus lacisalsi comb. nov.

A Gram-stain-positive, non-motile, mesophilic, aerobic, coccus-shaped bacterium, designated strain Y7R2T, was isolated from the brain of a Chiroteuthis picteti squid living in mesopelagic water near Muroto, Kochi, Japan. Phylogenetic analyses based on 16S rRNA gene sequences showed that the strain was most closely related to the genus Hoyosella (96.1 % similarity to the type strain of the type species Hoyosella altamirensis) and formed a separate distinct cluster in a stable, deep-branching lineage with the type strains of Hoyosella suaedae and Hoyosella lacisalsi (98.7-99.5% similarities). The major fatty acids (>10 %) of strain Y7R2T were C17 : 1 ω8c, C15 : 0, C16 : 1 ω6c/C16 : 1 ω7c and C16 : 0, and the isoprenoid quinones were menaquinone-7 (57.8 %) and menaquinone-8 (42.2 %). The principal polar lipids were phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol and phosphatidylinositol, and the DNA G+C content was 68.0 %. These chemotaxonomic features, with the exception of the fatty acid composition, were similar to those of the phylogenetically clustered species (H. suaedae and H. lacisalsi) but different from those of core Hoyosella species (including H. altamirensis). These results suggested that Y7R2T, H. suaedae and H. lacisalsi strains should be assigned to a novel genus. Furthermore, strain Y7R2T showed low average nucleotide identity values (88.0-88.2 %) and low digital DNA-DNA hybridization values (34.3-34.7 %) to the type strains of H. suaedae and H. lacisalsi. These data indicated that strain Y7R2T should be assigned to a novel genus and species, for which the name Lolliginicoccus levis gen. nov., sp. nov. is proposed. The type strain is Y7R2T (=NBRC 114883T=KCTC 49749T). Accordingly, reclassification of H. suaedae and H. lacisalsi as Lolliginicoccus suaedae comb. nov. (type species) and Lolliginicoccus lacisalsi comb. nov. is also proposed.

A retrospective study of pathologic findings in cephalopods (extant subclasses: Coleoidea and Nautiloidea) under laboratory and aquarium management.

This retrospective study examines pathologic findings in 593 captive cephalopods (340 octopuses, 130 cuttlefish, 33 squid, and 90 nautiluses; 22 species in total) submitted to International Zoo Veterinary Group Pathology between May 2003 and August 2022. Common octopus, European common cuttlefish, hummingbird bobtail squid, and chambered nautilus were the most numerous species from the included orders of Octopoda, Sepiida, Sepiolida, and Nautilida, respectively. Commonly identified conditions included coccidiosis and renal dicyemid mesozoan infection in octopuses, amebiasis in squid, bacterial infections in cuttlefish, and idiopathic multisystemic inflammatory disease in nautiluses. Coccidiosis was most frequent in common octopuses, giant Pacific octopuses, and California 2-spot octopuses (present in 68.4%, 46.3%, and 23.8% of these species, respectively) and was the attributed cause of death in 32.3%, 36.0%, and 60.0% of such cases, respectively. Ulcerative dermatitis (UD) was common, affecting squid, cuttlefish, and octopuses, while many nautiluses exhibited black shell disease and/or UD. Notable differences in the prevalence of UD were detected between laboratory and aquaria-housed decapodiforms; 52.2% for laboratory squid versus 20.0% in aquaria; 51.3% in laboratory cuttlefish versus 11.0% in aquaria. All octopuses and nautiluses in the study were derived from aquaria. Semelparity-associated death in Coleoidea species was identified in 22.4% of octopuses, 11.5% of cuttlefish, and 6.1% of squid. This report aims to provide an overview and reassessment of species-specific disease patterns under aquarium and laboratory management as a starting point for future developments in husbandry and disease investigation.

Ocular lesions of captive cephalopods.

Ocular lesions are uncommonly reported and described in invertebrate species. In this study, cases from 2 diagnostic laboratories, in which lesions were noted in 33 diagnostic specimens from various species of cephalopods, including octopuses, squid, nautiluses, and cuttlefish, were reviewed. Clinical information and gross lesions were described in a minority of cases. The most common lesion was inflammation of varying severity and was most commonly within the anterior uvea (iris and ciliary papilla), followed by the posterior chamber and lens. More than half of the cases with inflammation had concurrent hyperplastic lesions of the iris and ciliary papilla, including posterior iris epithelial hyperplasia, cystic adenomatous hyperplasia, and/or posterior epithelial cysts. The most common clinical observation was cloudy eyes, which correlated histologically to anterior uveitis in all cases where it was documented. Dermatitis and cutaneous ulceration were the most frequent comorbidities in cases where clinical information was available.

A peer-led, school-based social network intervention for young people in the UK, promoting sexual health via social media and conversations with friends: intervention development and optimisation of STASH.

BACKGROUND: The quality of school-based sex and relationships education (SRE) is variable in the UK. Digitally-based interventions can usefully supplement teacher-delivered lessons and positively impact sexual health knowledge. Designed to address gaps in core SRE knowledge, STASH (Sexually Transmitted infections And Sexual Health) is a peer-led social network intervention adapted from the successful ASSIST (A Stop Smoking in Schools Trial) model, and based on Diffusion of Innovation theory. This paper describes how the STASH intervention was developed and refined. METHODS: Drawing on the Six Steps in Quality Intervention Development (6SQuID) framework, we tested a provisional programme theory through three iterative stages -: 1) evidence synthesis; 2) intervention co-production; and 3) adaptation - which incorporated evidence review, stakeholder consultation, and website co-development and piloting with young people, sexual health specialists, and educators. Multi-method results were analysed in a matrix of commonalities and differences. RESULTS: Over 21 months, intervention development comprised 20 activities within the three stages. 1) We identified gaps in SRE provision and online resources (e.g. around sexual consent, pleasure, digital literacy), and confirmed critical components including the core ASSIST peer nomination process, the support of schools, and alignment to the national curriculum. We reviewed candidate social media platforms, ruling out all except Facebook on basis of functionality restrictions which precluded their use for our purposes. 2) Drawing on these findings, as well as relevant behaviour change theories and core elements of the ASSIST model, we co-developed new content with young people and other stakeholders, tailored to sexual health and to delivery via closed Facebook groups, as well as face-to-face conversations. 3) A pilot in one school highlighted practical considerations, including around peer nomination, recruitment, awareness raising, and boundaries to message sharing. From this, a revised STASH intervention and programme theory were co-developed with stakeholders. CONCLUSIONS: STASH intervention development required extensive adaptation from the ASSIST model. Although labour intensive, our robust co-development approach ensured that an optimised intervention was taken forward for feasibility testing. Evidencing a rigorous approach to operationalising existing intervention development guidance, this paper also highlights the significance of balancing competing stakeholder concerns, resource availability, and an ever-changing landscape for implementation. TRIAL REGISTRATION: ISRCTN97369178.

Yttrium-Iron Garnet Magnetometer in MEG: Advance towards Multi-Channel Arrays.

Recently, a new kind of sensor applicable in magnetoencephalography (MEG) has been presented: a solid-state yttrium-iron garnet magnetometer (YIGM). The feasibility of yttrium-iron garnet magnetometers (YIGMs) was demonstrated in an alpha-rhythm registration experiment. In this paper, we propose the analysis of lead-field matrices for different possible multi-channel on-scalp sensor layouts using YIGMs with respect to information theory. Real noise levels of the new sensor were used to compute signal-to-noise ratio (SNR) and total information capacity (TiC), and compared with corresponding metrics that can be obtained with well-established MEG systems based on superconducting quantum interference devices (SQUIDs) and optically pumped magnetometers (OPMs). The results showed that due to YIGMs' proximity to the subject's scalp, they outperform SQUIDs and OPMs at their respective noise levels in terms of SNR and TiC. However, the current noise levels of YIGM sensors are unfortunately insufficient for constructing a multichannel YIG-MEG system. This simulation study provides insight into the direction for further development of YIGM sensors to create a multi-channel MEG system, namely, by decreasing the noise levels of sensors.

A New Generation of OPM for High Dynamic and Large Bandwidth MEG: The 4He OPMs-First Applications in Healthy Volunteers.

MagnetoEncephaloGraphy (MEG) provides a measure of electrical activity in the brain at a millisecond time scale. From these signals, one can non-invasively derive the dynamics of brain activity. Conventional MEG systems (SQUID-MEG) use very low temperatures to achieve the necessary sensitivity. This leads to severe experimental and economical limitations. A new generation of MEG sensors is emerging: the optically pumped magnetometers (OPM). In OPM, an atomic gas enclosed in a glass cell is traversed by a laser beam whose modulation depends on the local magnetic field. MAG4Health is developing OPMs using Helium gas (4He-OPM). They operate at room temperature with a large dynamic range and a large frequency bandwidth and output natively a 3D vectorial measure of the magnetic field. In this study, five 4He-OPMs were compared to a classical SQUID-MEG system in a group of 18 volunteers to evaluate their experimental performances. Considering that the 4He-OPMs operate at real room temperature and can be placed directly on the head, our assumption was that 4He-OPMs would provide a reliable recording of physiological magnetic brain activity. Indeed, the results showed that the 4He-OPMs showed very similar results to the classical SQUID-MEG system by taking advantage of a shorter distance to the brain, despite having a lower sensitivity.