The research, published in Frontiers in Neuroimaging, is a trans-disease meta-analysis led by a team at Tianjin Medical University General Hospital in China. The investigators pooled voxel-based morphometry studies published between 2001 and 2024, assembling neuroimaging data from 2,070 patients with multiple sclerosis against 1,625 healthy controls, and 1,624 patients with Alzheimer’s disease against 1,607 healthy controls, drawn from 84 articles. Voxel-based morphometry is a technique that compares grey matter volume across the whole brain voxel by voxel, allowing researchers to detect regional shrinkage that often precedes symptoms. By statistically combining the peak coordinates of significant grey matter clusters from dozens of independent studies using the Seed-based Mapping software, the team produced disease-level atrophy maps of unusual statistical power.

The maps revealed a striking split. Multiple sclerosis-specific atrophy localized to the bilateral dorsomedial thalamic nucleus and the precentral gyrus — the deep grey matter and sensorimotor cortex that reflect the disease’s demyelinating character. Alzheimer’s-specific atrophy, in the age-unadjusted comparisons, centered on the bilateral hippocampus-amygdala complex, the medial temporal structures long known as the disease’s earliest casualties. Cytoarchitectonic mapping using the probabilistic Julich Brain Atlas added anatomical precision: the left hippocampal peak in Alzheimer’s disease was assigned to the CA1 subfield with a 52.5 percent probability, while the right parahippocampal peak fell within the laterobasal amygdala. The team also found that some of these between-disease differences, particularly in the thalamus and hippocampal-amygdala regions, were attenuated after age adjustment — a reminder that the twenty-year gap in typical onset age between the two conditions shapes part of the anatomical picture.

But the more consequential finding was the overlap. When the investigators computed the conjunction of the two atrophy maps, common grey matter loss emerged in the bilateral superior temporal gyrus, the insulae, the posterior cingulate cortex, the amygdalae, the right rectus gyrus, and striatal components including the caudate nucleus and putamen. These regions form the backbone of two major brain networks: the auditory-language network, anchored by the superior temporal gyrus, and the emotional processing network, a circuit spanning the amygdala, insula, orbitofrontal cortex, and striatum. Neurosynth decoding — a cross-sample spatial correlation between the atrophy map and thousands of brain activation maps for cognitive terms — confirmed the functional relevance, with the top terms encompassing speech production, auditory processing, face recognition, pain perception, and emotional regulation.

The convergence is not merely anatomical. Postmortem studies cited in the paper have documented pronounced cortical microglial activation in both multiple sclerosis and Alzheimer’s disease with closely similar patterns, and Alzheimer’s-type pathology, including beta-amyloid plaques and neurofibrillary tangles, has been identified in a subset of multiple sclerosis cases. Case reports have described patients with multiple sclerosis and progressive cognitive impairment who proved amyloid-positive and were subsequently diagnosed with coexisting Alzheimer’s disease. Conversely, recent work suggests that certain aspects of multiple sclerosis biology, or specific genetic factors in those patients, may offer unexpected protection against amyloid pathology — hinting at undiscovered neuroprotective crosstalk between the two conditions.

To probe the molecular underpinnings of the shared atrophy pattern, the team turned to spatial transcriptomics. They extracted gene expression profiles from the Allen Human Brain Atlas, a postmortem dataset mapping genome-wide expression across the adult human brain, and linked each tissue sample to the grey matter Z-value at its corresponding coordinate in the meta-analytic atrophy map. A partial least squares regression model then identified gene-expression patterns spatially associated with the atrophy profile. Of the five components estimated, PLS2 explained 13.10 percent of the variance and was the only one to survive a spatial autocorrelation-preserving permutation test — a critical safeguard, because brain maps are spatially smooth and naive statistics can inflate gene-imaging correlations. The PLS2 score correlated positively with the Z-scores of the overlapping atrophy regions, and 834 genes emerged as significantly associated with the common atrophy pattern, split into a positive set of 290 genes and a negative set of 544.

Functional enrichment analysis of these gene sets converged on four core biological themes: neurodegenerative injury, immune-inflammatory regulation, energy metabolic homeostasis, and synaptic-axonal maintenance. The positive-weighted genes predominantly encode how cells respond to internal and external stress — genomic damage, metabolic and energy challenges — and determine cellular fate through DNA stability maintenance, cell cycle arrest, metabolic remodeling, and quality control mechanisms such as mitophagy and apoptosis. This theme resonates deeply with established pathology. Mitochondrial dysfunction has been identified as a cause of axonal degeneration in multiple sclerosis, where energy deficits in demyelinated axons disrupt transport and promote cell death, while reduced mitochondrial density in Alzheimer’s disease signals an oxidative stress burden. The positive gene set also showed significant enrichment in adaptive immune cell differentiation and activation pathways, including T-cell receptor signaling — the very processes that drive inflammatory lesion formation in multiple sclerosis, where T-cell migration across the blood-brain barrier is a precondition for demyelination.

The negative-weighted genes tell the complementary story. They are functionally characterized by active suppression of excessive inflammation — inhibiting the production of interleukin-1 beta, interferon-beta, and interleukin-6 — along with specification of immune cell subsets such as marginal zone B cells and follicular dendritic cells, and maintenance of fundamental processes like DNA replication and synaptic vesicle transport. Cell-type-specific expression analysis showed the negative set was specifically expressed in immune cells, Pnoc-positive neurons of cortex, the habenula, and the hypothalamus, while the positive set was significantly expressed in the striatum. In other words, the shared atrophy pattern is spatially aligned with genes that both execute stress responses and actively restrain them — an immunological homeostasis imbalance that may represent the common molecular soil in which grey matter loss grows under two very different etiologies.

The authors are careful about what these findings do and do not mean. The spatial correlations link normative postmortem gene expression to disease-related atrophy; they are not evidence of differential gene expression in patients or direct causal effects of the identified genes on grey matter loss. Multiple sclerosis clinical subtypes carry distinct neurobiological features, and genetic heterogeneity across them could influence the results. Most importantly, because the two diseases have different primary neuropathological mechanisms, the shared atrophy regions and transcriptomic patterns may represent phenotypic outcomes induced by different disease processes rather than proof of a shared pathogenic mechanism — and the results cannot replace existing clinical diagnostic criteria for either condition.

Even with those caveats, the implications are considerable. The identification of a shared cortical-limbic-striatal atrophy nexus, validated across more than 6,900 brain scans and anchored to 834 genes spanning stress response, immune regulation, and energy metabolism, offers a template for transdiagnostic biomarkers of cognitive impairment and for therapeutic targets with relevance across disorders. The authors suggest that neuromodulation targeting the amygdala-insula-striatum circuit, such as transcranial magnetic stimulation, might simultaneously improve emotional symptoms in both conditions. As people with multiple sclerosis live longer and age into the risk window for neurodegenerative disease, the boundary between the two illnesses may matter less than the molecular machinery they share — and that machinery, this study argues, is now mapped.

Subject of Research: Neuroscience

Article Title: Grey matter atrophy signatures and their genetic associations: a trans-disease study of Alzheimer’s disease and multiple sclerosis

Article References: Zhao, Y., Sun, J., Reheman, B., Bai, X., Zhang, C., Ding, W., Zou, B., Zhang, H., Zhang, Z., & Zhang, N. (2026). Grey matter atrophy signatures and their genetic associations: a trans-disease study of Alzheimer’s disease and multiple sclerosis. Frontiers in Neuroimaging, 5, Article 1917609. https://doi.org/10.3389/fnimg.2026.1917609

Image Credits: AI Generated

DOI: 10.3389/fnimg.2026.1917609

Keywords: Alzheimer's disease, multiple sclerosis, grey matter atrophy, meta-analysis, spatial transcriptomics, Allen Human Brain Atlas, neuroimaging, neurodegeneration, gene expression, Frontiers in Neuroimaging, Grey, matter

Yet modern transient surveys have begun to uncover a handful of nearby PISN candidates, and SN 2018ibb stands out as one of the best identified to date. This Type Ic supernova exhibited a rise time exceeding 100 days and a peak luminosity around 10^44 erg s^-1, both consistent with theoretical PISN light-curve predictions. Its spectroscopic properties also matched expectations, including the strong [O III] emission characteristic of pair-instability explosions. However, late-phase spectra revealed an unexpected blue flux excess below approximately 5000 Å, a feature not predicted in standard PISN models. This excess was suggested to originate from the interaction between the supernova ejecta and dense circumstellar matter (CSM) surrounding the progenitor, implying an additional luminosity source beyond the radioactive decay of nickel-56.

To investigate this puzzle, a team led by Takashi J. Moriya of the National Astronomical Observatory of Japan developed synthetic light-curve models of PISNe interacting with dense CSM. The researchers adopted a PISN progenitor model computed with the KEPLER hydrodynamical stellar evolution code, using a bare helium star whose explosion energy and nickel-56 mass were determined self-consistently rather than treated as free parameters. The subsequent light curves were computed with the STELLA multi-frequency radiation hydrodynamics code, which solves hydrodynamic equations coupled with radiative transfer using the variable Eddington factor method across 100 wavelength bins. Based on the estimated metallicity of the host galaxy, they identified a model whose bolometric light curve matched the overall behavior of SN 2018ibb around peak luminosity, with properties consistent with previous independent estimates.

The team attached a wind-like CSM density structure on top of the ejecta, characterized by a mass-loss rate and CSM velocity. They assumed a CSM velocity of 1,000 km s^-1, corresponding to typical terminal wind speeds of Wolf-Rayet stars, and varied the mass-loss rate to adjust the CSM density. Within the investigated range, the CSM interaction had little effect on the light curve near peak. However, after approximately 150 days since explosion, the synthetic light curves with CSM began to deviate from those without, with increasing CSM density producing higher luminosity at later times.

The critical breakthrough came from matching the observed luminosity evolution of SN 2018ibb from 150 days after peak. The researchers found that a mass-loss rate of 0.01 (v_CSM/1,000 km s^-1) M_sun yr^-1 reproduced the bolometric luminosity well in the 300-day window following that epoch. More strikingly, SN 2018ibb showed a distinct luminosity break at around 300 days from peak. By varying the CSM radius while keeping the mass-loss rate fixed, the team demonstrated that this break is determined by the CSM radius, and the observed break could be reproduced by setting the dense CSM radius at 8.5×10^16 cm.

This radius carries profound implications for the progenitor’s final moments. Assuming a wind velocity of 1,000 km s^-1, the mass-loss rate must have increased to the inferred value for a period of 28 (v_CSM/1,000 km s^-1)^-1 years before explosion to place the CSM at the required distance. After the luminosity break, the synthetic light curves returned to the CSM-free prediction, indicating that the ejecta had swept past the dense material. However, the observed bolometric light curve of SN 2018ibb showed a flattening after the break, suggesting the supernova began interacting with less dense CSM beyond that boundary.

The team validated their numerical results using an analytic model of interaction-powered supernova luminosity, approximating the ejecta density structure with two power-law components. They found that the combined luminosity of the CSM-free PISN and the analytic interaction contribution reproduced the overall evolution until the break, with a kinetic-to-radiative conversion efficiency that matched the numerical model well. Notably, the CSM interaction luminosity contributed negligibly around peak, meaning PISN properties and CSM properties can be independently constrained from different phases of the light curve. The photospheric velocity evolution was also largely unaffected by CSM interaction, with the model’s g-band velocities roughly consistent with Fe II absorption-line measurements from SN 2018ibb.

The inferred mass-loss rate is far higher than expected from hot stellar winds of hydrogen-free stars, and if sustained over long timescales, the progenitor would have been stripped below the mass threshold required for a PISN explosion. The enhancement must therefore have occurred only in the final short period before detonation, consistent with the light-curve-derived timescale. Intriguingly, the progenitor model was found to trigger carbon shell burning after core contraction approximately 30 years before explosion, matching the estimated enhancement timescale. The core contraction with shell burning initiates progenitor expansion, which may drive the mass-loss enhancement. Alternatively, as the star approaches the dynamically unstable configuration triggered by pair creation, it may also enter a state conducive to enhanced mass loss.

Other mechanisms remain possible. The CSM could have formed through eruptive mass loss or binary mass transfer rather than a steady wind. Another intriguing possibility is that the mass-loss rate was not actually enhanced, but material lost from the progenitor accumulated near the stellar surface due to strong magnetic fields confining the stellar wind. Such magnetically confined material could remain close to the star and affect the PISN light curve in the manner observed. Further investigation is needed to determine whether magnetically confined CSM can extend to the inferred radius.

As PISN candidates accumulate, signatures of unexpected CSM interaction are emerging repeatedly. SN 2023vbw, another recent PISN candidate, also shows CSM interaction features. Because PISN progenitors require low overall mass loss to sustain their enormous masses, they were not expected to be surrounded by dense CSM. However, a significant fraction of supernovae from massive stars are now recognized to experience mass-loss enhancement within decades before explosion. PISN progenitors may undergo similar short-term enhanced mass loss, affecting their observational properties. Most predicted PISN characteristics to date ignore dense CSM, but models likely require updating. The presence of dense CSM is expected to make PISNe bluer than previously predicted, which could influence expected discovery rates at high redshifts and reshape our understanding of how the most massive stars die across cosmic time.

Subject of Research: Properties of the circumstellar matter around the pair-instability supernova candidate SN 2018ibb revealed by its light curve

Article Title: Properties of the circumstellar matter around the pair-instability supernova candidate SN 2018ibb revealed by its light curve

Article References: Moriya, T. J., Schulze, S., Heger, A., Blinnikov, S. I., & Potashov, M. S. (2026). Properties of the circumstellar matter around the pair-instability supernova candidate SN 2018ibb revealed by its light curve. Frontiers in Astronomy and Space Sciences, 13, Article 1944397. https://doi.org/10.3389/fspas.2026.1944397

Image Credits: AI Generated

DOI: 10.3389/fspas.2026.1944397

Keywords: pair-instability supernovae, SN 2018ibb, circumstellar matter, mass loss, massive stars, light curves, supernova ejecta interaction, stellar evolution, Properties, circumstellar, matter, around

The browning of coastal waters has emerged as one of the more visually striking signatures of global change in the marine realm. Across large stretches of the Northern Hemisphere, increasing runoff from land delivers terrigenous dissolved organic matter to the sea, staining coastal waters a tea-like amber colour and fundamentally altering the physics and chemistry of the underwater environment. This material, collectively referred to as coloured dissolved organic matter, or CDOM, originates largely from the decomposition of plant material in soils, wetlands, and forests. As precipitation patterns intensify and permafrost thaws, the flux of this terrestrial organic carbon into rivers and ultimately the coastal ocean is expected to rise substantially. While limnologists have studied lake browning for decades, its consequences for marine plankton communities have received comparatively less attention, partly because the open ocean has traditionally been viewed as too distant from terrestrial influences to be affected. The new mesocosm findings underscore that this assumption no longer holds for many coastal seas, where the interplay between land-derived organic matter and trace metal chemistry can reorganise the base of the food web.

The experimental approach behind these findings deserves particular attention because of the realism it offers. Mesocosm experiments occupy a valuable middle ground between laboratory cultures and field observations, allowing researchers to manipulate single variables while keeping an otherwise natural plankton community intact. In this study, large enclosed volumes of coastal seawater received additions of a humic substance as a source of CDOM and deferoxamine B, a strong iron-binding ligand, as a means of manipulating the speciation of dissolved iron. Deferoxamine B is a siderophore produced naturally by bacteria to acquire iron, and its use in experiments allows researchers to control how much iron remains biologically available. By combining these two treatments in a fully crossed design over 22 days, the team could separate the effects of light attenuation caused by browning from the effects of altered iron chemistry, and crucially, examine their interactions. This is important because in the real ocean these two stressors do not arrive independently; humic substances are themselves complexing agents that bind trace metals, meaning that increased terrigenous organic matter input changes not only the light field but also the chemical form and availability of iron.

The optical consequences of browning are more nuanced than simple darkening. CDOM absorbs strongly in the ultraviolet and blue portions of the spectrum, the very wavelengths that penetrate deepest in clear water and that many phytoplankton pigments exploit most efficiently. As terrigenous CDOM accumulates, the euphotic zone shoals, the spectral quality of available light shifts toward the green, and total photons reaching photosynthetic organisms decline. For large, slowly sinking phytoplankton species that depend on well-lit surface layers, these changes can be directly detrimental. Yet the experiment revealed a paradox: during the first eight days, small-sized phytoplankton actually increased their biomass under browning despite these unfavourable light conditions. The explanation lies in the dual nature of dissolved organic matter as both a screen and a substrate. Small phytoplankton and mixotrophic organisms can exploit dissolved organic compounds directly as a supplementary carbon and nutrient source, a capacity that compensates for reduced photosynthetic income. At the same time, the biomass gains suggest that growth under these conditions outpaced the grazing pressure exerted by microzooplankton, indicating that the net effect of browning on the smallest primary producers was initially positive rather than negative.

Iron chemistry sits at the heart of why this matters for ocean biogeochemistry. Iron is an essential micronutrient for phytoplankton, required for photosynthetic electron transport chains, nitrogen assimilation enzymes, and respiratory proteins. In vast regions of the ocean, iron availability limits primary production, and even in coastal waters where total iron concentrations are higher, the fraction that is truly bioavailable is governed by complexation with organic ligands. More than 99 percent of dissolved iron in seawater is typically bound to organic ligands, and the identity and origin of these ligands strongly influence whether microorganisms can access the metal. Terrestrial humic substances are increasingly recognised as important coastal ligands for iron. The experimental use of deferoxamine B to manipulate dissolved iron speciation therefore mimics a natural process: as browning intensifies, the organic ligand pool in coastal waters is augmented with terrigenous compounds that can hold iron in solution and potentially deliver it across microbial cell membranes. The finding that both phytoplankton succession and microzooplankton dynamics responded to altered iron speciation demonstrates that climate-driven changes in organic matter inputs propagate through the food web partly via trace metal chemistry, a pathway that is often overlooked in favour of purely optical or carbon-centric framing.

The temporal structure of the observed responses carries its own lessons. The benefits of browning for small phytoplankton were confined to roughly the first half of the experiment; during the second half, no changes attributable to browning were detected. This transient response pattern likely reflects the exhaustion of labile components of the added organic matter, adaptive adjustments by grazers, or the reorganisation of the community toward a new quasi-equilibrium. It also echoes a recurring theme in mesocosm research: the earliest days of a manipulation often capture the most dramatic effects, while communities buffer and reorganise over time. For ecosystem managers and modellers, this suggests that the consequences of pulsed terrigenous organic matter inputs, such as those following storm-driven runoff events, may be most pronounced in the days immediately following the pulse, even if the standing community recovers subsequently.

Perhaps the most consequential phase of the experiment came with the crash of both phytoplankton and microzooplankton populations under intense mesozooplankton grazing. This top-down control illustrates a fundamental feature of plankton ecosystems: the fate of bottom-up stimulation, whether from nutrient enrichment or organic matter subsidisation, is ultimately determined by the grazing community. Copepods and other mesozooplankton graze not only the phytoplankton directly but also, through their consumption of microzooplankton, exert cascading control over the microbial loop. The authors’ hypothesis that browning and altered iron availability could favour the vertical migration of mesozooplankton toward the surface in a darkening ocean adds a behavioural dimension to these biogeochemical and optical effects. Zooplankton vertical migration is among the largest organised animal movements on Earth, and it plays a central role in the biological carbon pump through the active transport of carbon to depth. If darker surface waters alter the trade-off between feeding opportunity in the surface and predation risk in the illuminated layer, the depth, timing, and intensity of migration could shift, with cascading consequences for carbon export, food web coupling, and the efficiency of energy transfer to fish larvae that depend on grazing zooplankton.

The broader climatic context amplifies the significance of these coastal findings. Coastal seas disproportionately matter for global biogeochemical cycling relative to their area; they host a large share of global fisheries landings, bury substantial amounts of organic carbon in sediments, and mediate the transfer of terrigenous material to the open ocean. Changes in the structure of coastal plankton communities therefore ripple outward, affecting carbon sequestration, the productivity of commercially important stocks, and the transport of organic matter and metals across the shelf. Furthermore, browning interacts with other simultaneous stressors, including ocean warming, acidification, deoxygenation, and eutrophication. Darker waters warm differently because absorbed radiation is trapped nearer the surface, stratification patterns change, and the balance between heterotrophic and autotrophic processing of carbon may tip toward respiration and CO2 outgassing. The demonstration that CDOM and iron jointly reshape phytoplankton succession and zooplankton behaviour provides an empirical foundation for incorporating these linkages into Earth system models, which historically represent coastal processes in highly simplified ways.

Finally, the study highlights the value of long-running European mesocosm infrastructure and international collaboration in addressing questions that no single nation or discipline could resolve alone. The combination of expertise in algal physiology, trace metal chemistry, optical ecology, and zooplankton behaviour was essential to disentangle the mechanisms at play. As climate change continues to intensify the hydrological cycle and mobilise terrigenous carbon from soils, experiments of this kind, conducted over ecologically meaningful timescales with realistic manipulations, will be indispensable for anticipating how the microscopic communities at the base of the marine food web will reorganise. The picture that emerges is one of an ocean whose colour is not merely an aesthetic signature of change but an active driver of ecological and biogeochemical transformation, mediated as much by metal-ligand chemistry and animal behaviour as by the amount of light reaching the cells that anchor nearly all marine food webs.

Subject of Research: …

Article Title: Coloured Dissolved Organic Matter and Iron Rewire the Marine Plankton Food Web in a Changing Climate

Article References: Segovia, M., Ramírez, L., Vázquez, V., Arnone, V., González-Santana, D., León, P., Santana-González, C., Santana-Casiano, M., González-Dávila, M., Tsagaraki, T. M., Smerdou, C., López-Parages, M., Macías, M., Nejstgaard, J. C., Cañete, S., Berger, S. A., Egge, J. K., & Larsen, A. (2026). Coloured Dissolved Organic Matter and Iron Rewire the Marine Plankton Food Web in a Changing Climate. Microbial Ecology. https://doi.org/10.1007/s00248-026-02856-6

Image Credits: AI Generated

DOI: 10.1007/s00248-026-02856-6

Keywords: Coloured, Dissolved, Organic, Matter, Iron, Rewire, Marine, Plankton, Food, Changing, Climate, scientific research