Juvenile Great Hammerhead Sharks Rely On South Florida’s Biscayne Bay

Catherine Macdonald, Ph.D., a co-author of the study and director of the Shark Research and Conservation Program at the University of Miami Rosenstiel School, reviews a mark-recapture tag as part of the data collected during the study. CREDIT: University of Miami Shark Research and Conservation Program

 June 17, 2025  0 Comments

By Eurasia Review

A new study from the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science finds that juvenile great hammerhead sharks (Sphyrna mokarran), a critically endangered species, rely heavily on the resources of Florida’s Biscayne Bay as a nursery habitat during their earliest and most vulnerable years.

Nestled within the heart of the Miami metropolitan area, Biscayne Bay is a shallow, subtropical estuary known for its clear waters and ecological richness. However, in recent decades, the bay has suffered from declining water quality, reduced freshwater inflow, and physical degradation—largely driven by urban development and rapid population growth—posing growing risks to the species that depend on it.

“We analyzed the feeding and habitat use patterns of 62 great hammerheads sampled between 2018 and 2025,” said John Hlavin, the lead author of the study and a doctoral student in the Department of Environmental Science and Policy at the Rosenstiel School. “Our team employed a research technique called multi-tissue stable isotope analysis to track both short and long-term resource use, allowing us to gain new insights into the species’ dietary habits across different life stages.”

The findings indicate that young sharks rely on Biscayne Bay’s shallow inshore habitats and prey species year-round for the first two years of their life. After age two, subadult hammerheads shift to foraging on coastal reefs, but return to Biscayne Bay seasonally, from late spring through early summer. Many adult hammerheads continue to feed on bay resources, indicating that nearshore habitats remain important throughout the great hammerhead’s life cycle.

“Juvenile great hammerheads show a constrained diet and habitat use, potentially feeding heavily on small inshore stingrays early in life,” said Catherine Macdonald, a research associate professor in the Department of Environmental Science and Policy, and the director of the Shark Research and Conservation Program at the Rosenstiel School. “This reliance on a narrow range of prey and habitats makes juvenile great hammerheads particularly vulnerable to human activity and environmental change.”

Miami is a popular recreational fishing destination; however, great hammerheads are exceptionally sensitive to capture stress. The study’s findings point to a need for responsible fishing practices, especially from March through July, when both juveniles and subadults inhabit the bay.

“Reducing interactions with these sharks—particularly avoiding catch-and-release fishing in key nursery areas—can dramatically improve survival for this endangered species,” said Hlavin. “If a shark is accidentally caught, the best action is a quick, in-water release, without photographs that delay the release process.”

Methodology

Researchers used stable isotope ratios of carbon and nitrogen in muscle and blood plasma samples to evaluate great hammerhead diet and habitat use across age classes and seasons. This non-lethal method provides insights into both recent and long-term feeding behaviors, revealing how their reliance on Biscayne Bay changes as these sharks mature.

A call for increased conservation measures

This study offers critical data to inform conservation strategies and marine policy in Florida and beyond. Protecting essential nursery habitats like Biscayne Bay are vital to giving great hammerheads a fighting chance in the face of environmental degradation, habitat loss and overfishing.

This research was supported by the National Geographic Society, Nature Trust of the Americas, Florida Sea Grant-Guy Harvey Fellowship, and the Annual Mary Roche Fellowship at the University of Miami Rosenstiel School.

The study titled, “Nursery resource use dynamics in great hammerheads (Sphyrna mokarran) across ontogeny,” was published in the journal Ecology and Evolution on June 15, 2025. The authors are John F. Hlavin*1,2, Catherine C. Macdonald1,2

Notes:

1.Shark Research and Conservation Program, University of Miami Rosenstiel School for Marine, Atmospheric, and Earth Science, Miami, Florida. 

2. Field School Scientific Training, Coconut Grove, Florida.

 

Krill Fishing In The Antarctic: Overlaps With Consequences

In search of krill, fishing vessels in the Southern Ocean encounter penguins during their main breeding season in the immediate vicinity of their breeding colonies. CREDIT: Alfred-Wegener-Institut / Dominik Bahlburg

 June 17, 2025  

By Eurasia Review

Antarctic krill is a key species in the Antarctic marine ecosystem: it is an important food source for many species, such as whales, seals and penguins. However, the small crustaceans are increasingly becoming the focus of fishing, which can incur significant consequences for the entire Southern Ocean ecosystem. Therefore, concepts that minimize the negative effects of fishing on the krill themselves and on the animals that feed on krill are required urgently.

A research team from the Alfred Wegener Institute and the Norwegian Institute of Marine Research in Bergen has now been able to use acoustic recordings, that fishing vessels routinely record, to identify areas and periods in which there is an increased overlap between fishing and krill predators. The results can contribute to developing effective management strategies to protect the Antarctic ecosystem. The study will be published in the Proceedings of the National Academy of Sciences journal.

“In conducting our study, together with our colleagues from Norway, we analyzed more than 30,000 hours of echo sounder recordings collected by three krill fishing vessels in the Southern Ocean over a period of six years,” as Dominik Bahlburg from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), stated. Using a segmentation model and artificial intelligence, the researchers were able to filter out signals that whales, penguins and seals emit when they dive under fishing vessels. “During such encounters, ships and krill predators pursue the same krill swarms. This allowed us to systematically analyse the spatial and temporal dynamics of this competition in order to identify locations and time periods where the interaction between the two groups is particularly intensive.”

This showed up distinct seasonal patterns that were specific to the various krill predators. For example, the fishery encountered penguins and fur seals in summer and winter, particularly in the South Orkney Islands and South Georgia, while only rarely encountering whales. “The South Orkney Islands seem to be a real hotspot for encounters with penguins,” says Dominik Bahlburg. “Compared to the Antarctic Peninsula, they have received far less attention in the debate on the impact of krill fishing and many of the colonies affected there are currently not regularly monitored.” This, however, would be ecologically significant, as fishing vessels encounter penguins here in summer during their main breeding season, in the immediate vicinity of their breeding colonies. This furthermore suggests that restriction zones on the Antarctic Peninsula, that have been established voluntarily by the fishery, do not really minimize the encounters of penguins and vessels and thus the direct competition for krill during the breeding season, but rather shifted them to the South Orkney Islands.

Another aspect took the authors by surprise: “We were able to show that fisheries and penguins as well as fur seals encounter each other just as frequently in the winter as in the summer season.” As the animals are not tied to their colonies at this time and are often widely dispersed, the fact that krill fishing has increasingly focussed on the wintertime was previously seen as a positive development. “However, the fact that the animals are now also encountering ships so frequently at this time may require a reassessment of this development.” Compared to the South Orkney Islands, seals and penguins were rarely encountered in the echo sounder data from the Antarctic Peninsula. Especially in the autumn, fishing here competes intensively with whales for krill. At this time, whales build up their fat reserves for their subsequent migrations to their breeding grounds towards the equator.

Reliable data for better protection of the Antarctic Ocean ecosystem 

“Remarkably, these patterns were quite stable for seals, penguins and whales over a six-year period,” as Sebastian Menze from the Norwegian Institute of Marine Research related. “Consequently, our results show that acoustic data from fishing vessels and machine learning can act as a reliable foundation for rapid and convenient assessments of fisheries’ interaction with the ecosystem.” They offer tremendous temporal and spatial coverage, as the vessels are travelling in different locations in the Southern Ocean almost all year round. What’s more, recording the data is particularly cost-effective, as it can be collected as a kind of “by-product” of fishing. The data used in this study by the largest krill fishing company (Aker Biomarine) is even accessible via a public data platform (HUBOcean).

To date, echo sounder data from krill fishery has only been used sporadically for scientific purposes, for example to estimate the biomass of krill. “Thanks to our approach, we are expanding the potential uses for ecological questions and demonstrating new, cost-effective ways in which fishing vessels can actively contribute to krill fishery management,” emphasises Bettina Meyer, scientist at the AWI and German scientific representative in the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). “Acoustic data make it possible to quickly draw an initial picture of how changes in fishery management or fleet behaviour impact on the Antarctic ecosystem. This is particularly significant for periods of time or areas that are not well covered by existing research programmes.”

The study was funded by the German Federal Ministry of Food and Agriculture in order to effectively contribute the findings to CCAMLR’s efforts to improve the management of krill fisheries. In future, such analyses can also help to evaluate the effectiveness of existing and future management measures and optimise them where necessary.

 

Climate Change And Interactions Between Species Are Changing Distribution Of Brown Bears In Europe

Brown bear (Ursus arctos) feeding on fruit in a mixed forest CREDIT: Vincenzo Penteriani

 June 17, 2025 

By Eurasia Review

An international team led by the University of Seville, La Sapienza University of Rome and the Institute of Nature Conservation in Poland has studied how interactions between species affect the distribution of brown bears in Europe and Turkey.

It has been found that the distribution of bears on a continental scale is largely explained by interaction with other species: specifically, bears occupy areas where the species that form part of their diet are distributed. The research, published in the journal Global Change Biology, shows the importance of interactions between species on a continental scale, using the brown bear as a case study. 

Understanding how global changes – such as climate change or land use transformation – affect species is critical to conserving biodiversity and maintaining the benefits that nature provides, such as clean water, soil fertility and pollination.

For example, as a result of climate change, the distribution of some species is shifting to higher altitudes or towards the poles, where climatic conditions remain within the species’ tolerances. Until now, most studies have focused only on the importance of direct changes, such as changes in temperature, rainfall or agricultural use, on species distributions. However, this work has turned the spotlight on indirect effects through interactions between species.

“The bears showed a very varied diet: we detected 276 species in their diet. Bears living in warmer places, such as sub-populations in the Cantabrian Mountains, Greece or Turkey, have a more vegetarian diet, while in colder areas such as Scandinavia and Finland, bears are more carnivorous. This means that the role of bears in the ecosystem/food chain is different, varying between herbivore and apex predator,” explains US researcher Pablo M. Lucas.

“Thanks to our large international team, we had more than three million bear locations, corresponding to some 3,000 bears and, very importantly, data from the 14 European and Turkish sub-populations, which inhabit very different environments. This allowed us to study the effects of local interactions over a continental area. We observed that bears occupy those places where the most energy from the species in their diet is available. For example, in the Cantabrian Mountains, the presence of oak and beech trees, which are the main food source for this sub-population, makes the presence of bears more likely; in other sub-populations where bears are more carnivorous, the presence of bears is better explained by the distribution of wild ungulates such as wild boar and deer.”

This information is particularly important for predicting where species will live in the future and what roles they play in ecosystems, in a context of climate change and land use transformation, and for understanding that in order to protect species, we must conserve the ecosystems where they live. ‘Changes in the distribution of the species they feed on may affect the bear’s position in the food chain and the viability of the species at the local level,’ the researcher points out.

Other species with characteristics different from those of brown bears – such as a more specialised diet, less ability to move, or the ability to live only in very specific environmental conditions – may react differently to climate change, land use transformation, and changes in the species with which they interact. Improving this knowledge is essential for designing more effective strategies for conserving biodiversity and the services that nature provides us.

This work was carried out by a team of 87 researchers from 75 institutions in 26 countries, led by a researcher from the University of Seville (US). In addition to the US, other Spanish institutions are involved, such as the National Museum of Natural Sciences (MNCN-CSIC), the Doñana Biological Station (EBD-CSIC) and the University of Huelva. 

 

Jamaat-E-Islami’s Ideological Deep State: A Theocratic Undercurrent In South Asia’s Secular Crises – Analysis

Protestors with the Bangladesh flag. Photo Credit: Tasnim News Agency

 June 17, 2025

By Observer Research Foundation

By Soumya Awasthi and Mehraj Bhat

In a politically charged move, Bangladesh may soon witness the re-entry of Jamaat-e-Islami (JeI) into electoral politics, according to a recent media report. Despite being banned from contesting polls since 2013 due to its theocratic foundations and the role of its leaders in the 1971 genocide, JeI now seeks re-legitimisation by floating new proxies.

This development comes amid growing political instability and rising pressure on former Prime Minister (PM) Sheikh Hasina’s government, creating a fertile ground for reactivating ideological forces that were once considered defanged. However, to view this merely as a case of electoral opportunism would mean turning a blind eye to a far more insidious reality: JeI is not just a political party—it is a civilisational project, an ambitious ideological paradigm intent on transfiguring socio-political infrastructure into a theocentric order.

Despite decades of state repression, juridical proscription, and robust political opposition, JeI exhibits an extraordinary capacity for strategic reinvention and doctrinal persistence across Pakistan, Bangladesh, and Jammu & Kashmir. Its ideological tenacity, institutional elasticity, and subterranean influence form a complex web of geopolitical implications that regional powers—particularly India—cannot afford to underestimate. This article explores JeI’s theocratic infrastructure, subterranean operations, and civilisational agenda, arguing that it represents not a peripheral radical outfit but a structured ideological insurgency.

The Theocratic Blueprint: Maududi’s Doctrine and JeI’s Civilisational Mission

Established in 1941 by Maulana Abul A’la Maududi, Jamaat-e-Islami has rarely been content with mere electoral participation. Its ambitions have always been more expansive: to reorder society along divine lines, subordinating law, education, the economy, and governance to a theocentric order. JeI’s approach is distinct from conventional jihadist outfits, which primarily rely on militancy. Instead, it follows a meticulous and long-term strategy of ideological subversion—what Maududi observed as a ‘cultural revolution from below’. By embedding its doctrine into societal institutions—such as schools, mosques, welfare trusts, and student organisations—JeI has created an enduring epistemic infrastructure.

Its rejection of secular modernity is foundational. Democracy, in JeI’s cosmology, is heretical unless it aligns with divine jurisprudence. Yet paradoxically, JeI often enters democratic spaces not to participate in them sincerely but to hollow them out from within. It leverages democratic legitimacy to launch a critique of democracy itself, advancing a vision that ultimately seeks to dissolve the constitutional order in favour of a divine polity.

Pakistan: Parasitic Partnership with the Military Establishment

Nowhere is the symbiosis between JeI and the state apparatus more entrenched than in Pakistan. While it has never commanded significant electoral clout, JeI has long been an ideological arm of Pakistan’s military elite. During General Zia-ul-Haq’s Islamisation drive, JeI embedded itself in the state’s intellectual and educational bloodstream—producing curricula, occupying key bureaucratic posts, and controlling a vast network of madrasas.

Its student wing—Islami Jamiat-e-Talaba (IJT)—remains a formidable force in universities, functioning both as an enforcer of moral orthodoxy and a recruiter of ideological cadres. This deep ideological encapsulation has allowed JeI to shape public discourse, sustain Islamist narratives, and perpetuate a shadow state that survives regardless of electoral fortunes. As Islamabad oscillates between military and civilian rule, JeI’s ideological machinery remains impervious, lubricated by state patronage and religious populism.

Bangladesh: Rebranding After Repression

JeI’s history in Bangladesh is indelibly marked by its role in the 1971 genocide, during which its paramilitary wing—Al-Badr—collaborated with the Pakistan Army. Although JeI was banned after independence, it was rehabilitated later through political compromises and shifting geopolitical priorities. The war crimes tribunalinitiated by the Awami League after 2008 aimed to amputate JeI’s political legacy, culminating in the execution of several top leaders.

Nonetheless, the core ideology endured. Chhatra Shibir, its student front, remains active in educational institutions, while JeI-controlled businesses and charities offer social services in rural and underserved areas. The recent move to field candidates under new banners is not a deviation but a continuation of JeI’s strategy of ideological camouflage. Despite constitutional embargoes, JeI has never truly exited the political field; it has merely changed its apparel. As Hasina’s regime grapples with economic discontentment and political backlash, JeI’s re-entry signifies more than opportunism—a potential re-ignition of theological politics in the region.

Jammu & Kashmir: Theology as Resistance

In India’s Jammu & Kashmir, JeI has played an integral role in transforming a political conflict into an Islamic civilisational struggle. It capitalised on post-1987 electoral disillusionment to propagate an Islamist narrative that delegitimised secular resistance and promoted a religiously encoded insurgency. JeI’s strategy involved setting up a parallel civil infrastructure—mosques, schools, welfare trusts—that challenged state authority and redefined societal norms.

Despite being banned multiple times—most recently in 2019—JeI’s intellectual grammar remains intertwined with the region’s socio-political psyche. Its methodical proliferation of mosque networks, madrasa systems, and welfare apparatuses created a parallel civil society, functioning as a state-in-waiting and a normative re-educator. It is not simply an organisation to be banned; it is an ideological matrix that recalibrates the Kashmiri identity around theological nationalism. The persistence of this epistemic framework poses long-term security and integration challenges for India, especially as new political voids emerge.

Geopolitical Ramifications: India’s Strategic Dilemma

The reactivation of JeI in Bangladesh, its ideological penetration in Pakistan, and its subterranean resilience in Kashmir constitute a tripartite challenge to India’s regional security architecture. Unlike transnational jihadist networks, JeI operates through localised institutions with global ideological ties. Its soft power—via educational outreach, social welfare, and religious discourse—allows it to remain undetected by conventional counter-terrorism frameworks.

Furthermore, JeI serves as a conduit for larger pan-Islamist currents that find resonance in other ideological outfits across South and Central Asia. Its resurgence in Bangladesh—particularly during a politically vulnerable moment—may destabilise the region and recalibrate the strategic calculus of both Delhi and Dhaka. India’s counter-insurgency efforts in Kashmir will also remain incomplete without addressing the ideological ecosystem that JeI has cultivated over the decades.

Conclusion: An Embedded Worldview, Not Just a Banned Outfit

To view Jamaat-e-Islami as a radical party is to fundamentally misunderstand its essence. It is a paradigmatic insurgency nested within civil society, functioning like an ideological deep state that erodes the foundations of secular constitutionalism. Its operatives are not merely political activists but cultural engineers working to transform state institutions from within. The challenge it poses cannot be countered by electoral disqualification or organisational bans alone.

Policymakers must confront the full spectrum of JeI’s operational vectors—its student fronts, welfare agencies, publishing houses, and educational networks. The ideological war must be waged in classrooms, community halls, religious forums, and policy debates. Any attempt to co-opt, moderate, or ignore JeI will only play into its strategies of mimetic legitimacy and long-term infiltration. JeI thrives not in open confrontation but in subtle subversion.

Its endurance across disparate political systems—military authoritarianism in Pakistan, democratic authoritarianism in Bangladesh, and constitutional democracy in India—underscores a disturbing reality: this is not a political party; it is the resilience of a worldview. Dislodging it will require more than strategy—it will require ideological courage.

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About the authors:

• Soumya Awasthi is a Fellow with the Centre for Security, Strategy, and Technology at Observer Research Foundation.
• Mehraj Bhat is a Srinagar-based expert on Islamic studies. He is studying the role of Jamaat-e-Islami in South Asian Politics.

Source: This article was published by Observer Research Foundation

Observer Research Foundation

ORF was established on 5 September 1990 as a private, not for profit, ’think tank’ to influence public policy formulation. The Foundation brought together, for the first time, leading Indian economists and policymakers to present An Agenda for Economic Reforms in India. The idea was to help develop a consensus in favour of economic reforms.

Scientists Are Getting Closer to Finding Evidence of the Fifth Force

If it’s out there, could we observe it soon?

By Darren Orf

Published: Jun 14, 2025

 Popular Mechanics

 


Here’s what you’ll learn when you read this story:Some physicists believe that a fifth fundamental force could be the cause of some observational anomalies.
A study is investigating ways to closely examine the trajectories of well-documented asteroids to hopefully detect anomalies that could provide evidence of such a force.
Although the study shows no fifth force anomaly present in the asteroid Bennu, future explorations of the asteroid Apophis could provide an even better chance to find this elusive force—if it exists at all.

According to the current Standard Model, four fundamental forces underpin all known physics: electromagnetism, gravity, and the strong and weak nuclear forces. However, since the mid-1980s, physicists have wondered if a fifth fundamental force could exist, which would help to explain some observational anomalies. And since then, many studies have boldly claimed discovery of this elusive force.

In 1986, for example, scientists at MIT thought that antigravity could maybe could be a fifth force, and in 2000, another group named the force “quintessence” as a way to explain dark energy. In 2015, a study by the Hungarian Academy of Sciences discovered a particle 30 times heavier than an electron that could form the basis of a fifth force, and the U.S.-based Fermilab stated boldly that they were on the cusp of discovering this mysterious force in 2023.

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And, of course, there’s a strong contingent of physicists who think a fifth force doesn’t exist at all.

One proposed way of examining if such a force could exist is by closely monitoring asteroid trajectories, and few near-Earth asteroids are as well observed as Bennu. A study by an international team of scientists analyzes Bennu to try and placing constraints on a possible fifth fundamental force in the search of ultralight dark matter.

Bennu, one of the most dangerous near-Earth objects, has been meticulously tracked by optical and radar astrometric data since it was discovered in 1999. As the destination for the OSIRIS-REx asteroid retrieval mission, additional X-band radiometric and optical navigation tracking data added even more trajectory precision.

The idea is that any deviation in the expected trajectory of the asteroid could be the result of an unknown fifth force at work. The results of the study were published in the journal Nature Communications Physics.

“Interpreting the data we see from tracking Bennu has the potential to add to our understanding of the theoretical underpinnings of the universe, potentially revamping our understanding of the Standard Model of physics, gravity and dark matter,” Yu-Dai Tsai, the lead author on the paper, said in a press statement. “The trajectories of objects often feature anomalies that can be useful in discovering new physics.”

The trajectories of heavenly objects have yielded incredible discoveries before. Neptune, for example, was first “discovered” not through a telescope, but by the meticulous calculations of Uranus’ orbit and discovery of gravitational anomalies therein. However, such a technique isn’t foolproof, as some scientists also believed that a planet named Vulcan existed between the Sun and Mercury. This, obviously, turned out to be false.
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“These results highlight the potential for asteroid tracking as a valuable tool in the search for ultralight bosons, dark matter, and several well-motivated extensions of the Standard Model,” Sunny Vagnozzi, assistant professor at the University of Trento in Italy and study co-author, said in a press statement.

While this study didn’t find “evidence in the data for the presence of a fifth force affecting the motion of Bennu,” the ORSIRIS-REx’s sequel, OSIRIS-APEX, could provide even more data as the mission zooms onward toward the asteroid Apophis. Because this asteroid will zoom by Earth in 2029, a detailed study of its trajectory will deliver even further restrictions on the fifth force than what Bennu could provide.

So, while the ongoing exploration of the fifth force continues in accelerator labs around the world, some scientists are turning toward space to answer the deepest mysteries of physics.

Darren Orf
Contributing Editor
Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.

Psilocybin induces large-scale brain network reorganization, offering insights into the psychedelic state

by Eric W. Dolan
June 14, 2025
 PsyPost .



A new study published in Translational Psychiatry has provided the most detailed look yet at how psilocybin affects brain activity in rodents. Researchers found that psilocybin produces widespread changes in brain network organization, disrupting normal patterns of communication between brain regions and creating a unique state of high-frequency neural connectivity. These effects varied depending on dose and time, revealing two distinct phases of brain dynamics.

Psilocybin is the active compound found in certain mushrooms and has gained attention for its potential to treat conditions such as depression, anxiety, and addiction. When consumed, psilocybin is converted into psilocin, a substance that binds to serotonin receptors in the brain and produces profound changes in perception, emotion, and sense of self. In humans, psilocybin is known to temporarily alter how different parts of the brain interact, but less is known about how these effects emerge over time or whether animal models can capture the complexity of the psychedelic state.

“We use neurochemical and neurophysiological approaches, including brain network changes, to understand the mechanistic basis of different states of consciousness and our ongoing work with psychedelics is another step in that direction,” explained study author Dinesh Pal, an associate professor at the University of Michigan.

“One of the primary challenges of studying psychedelics in animal models is the lack of a verbal report, but that also makes it fascinating, because any evidence (e.g., EEG based metrics) for a ‘psychedelic’ state in animal models, akin to what occurs in humans, would bring us closer to the idea that consciousness is a universal phenomenon; it just manifests in different ways in different species.”

To address this, the researchers used high-resolution electroencephalography (EEG) to monitor brain activity across 27 sites in the rat cortex. EEG is a noninvasive technique that measures electrical activity in the brain using sensors placed on the scalp. It records the brain’s natural oscillations, or “brain waves,” which reflect patterns of neural communication across different regions. The goal was to map how psilocybin changes the organization of brain networks and to identify specific patterns of activity that might reflect altered states of consciousness.

The study involved 12 adult Sprague Dawley rats—six male and six female—that were surgically implanted with EEG electrodes. Each rat received intravenous infusions of psilocybin at three different doses (0.1, 1, and 10 milligrams per kilogram), as well as a saline control, on separate days. The researchers recorded EEG data before, during, and after each 60-minute infusion and also monitored behavior through video recordings and movement sensors. By using a continuous infusion method rather than a single injection, the researchers were able to observe gradual changes in brain activity as the drug took effect.


The team focused on three specific frequency bands in the EEG data: theta (4–10 Hz), medium gamma (70–110 Hz), and high gamma (110–150 Hz). These frequencies are thought to play a role in coordinating communication between brain regions. Psilocybin altered both the strength and organization of activity in these bands, but not in a simple or linear way.

At moderate doses (1 mg/kg), psilocybin increased activity in the posterior theta network and strengthened communication between frontal and parietal brain areas in the gamma bands. This state was marked by widespread increases in high gamma activity in the frontal cortex and greater connectivity across distant brain regions. The researchers also found that psilocybin disrupted the normal relationship between theta and gamma activity, a phenomenon known as phase-amplitude coupling. This decoupling was most evident in frontal areas and occurred in a dose-dependent fashion.

At higher doses (10 mg/kg), a different pattern emerged. Early in the infusion, the brain showed a similar increase in gamma connectivity, but as the dose accumulated, theta connectivity in posterior regions decreased, and the gamma network in the frontal cortex became more dominant. These changes unfolded over time, revealing a shift from one state of brain organization to another as psilocybin levels rose. Notably, these effects occurred even as the rats became less physically active, suggesting the brain changes were not simply a result of movement or arousal.


The behavioral data supported this nonlinear pattern. Moderate doses of psilocybin increased the number of head-twitch responses—a common indicator of psychedelic activity in rodents—and briefly heightened movement. But at the highest dose, movement decreased significantly after about 30 minutes, even though gamma connectivity continued to increase. This suggests that the changes in brain dynamics were not just reflections of behavior but may correspond to a unique internal state.

“It was a bit surprising to note that the changes in EEG gamma connectivity – shown to be closely linked to states of consciousness – occurred in the absence of any behavioral activity or after the psilocybin-induced locomotion and/or head twitches ceased,” Pal told PsyPost. “This dissociation suggests the need for a careful assessment of head twitch response as a surrogate for psychedelic or non-ordinary states induced by psychedelic drugs in rodents.”

To quantify brain network organization, the researchers used measures such as node degree (the number of connections a brain region has) and the strength of synchronization between regions. These metrics showed that psilocybin reorganized networks in both frequency-specific and region-specific ways. The theta network, typically involved in memory and attention, became stronger in posterior regions at moderate doses but weakened at higher doses. In contrast, the high gamma network, which is thought to reflect localized activity and potentially neuroplasticity, became stronger in frontal areas as the dose increased.


One of the most striking findings was the decoupling of gamma activity from the theta phase. Under normal conditions, gamma bursts tend to occur at specific points in the theta rhythm, a coupling that is thought to help organize information flow in the brain. Psilocybin disrupted this timing relationship, particularly at higher doses, suggesting a breakdown in the usual coordination between local and long-range neural signals. This kind of decoupling has been observed in other psychedelic states and is believed to reflect a loosening of the brain’s typical constraints, allowing for more flexible or unusual patterns of thought and perception.

While the study does not prove that rats experience anything like a human psychedelic trip, the results suggest that the psilocybin state is marked by identifiable changes in brain network architecture that can be studied in animal models. These findings align with reports from human studies showing increased connectivity between distant brain regions and decreased segregation of functional networks during psychedelic experiences.

“Our findings related to brain network changes in this study, along with the data from other laboratories showing cellular and molecular level neural changes, show that rodents could indeed be a good model system to study non-ordinary states of consciousness such as a psychedelic state,” Pal said.


But there are important limitations to consider. Because rodents cannot report their subjective experiences, the researchers could not directly link changes in brain activity to changes in perception or emotion. Also, although the results support a role for serotonin receptor signaling, the study did not manipulate specific receptors to determine their causal role. Additionally, the EEG method used in this study does not measure deep brain structures like the thalamus or claustrum, which are also thought to be involved in the psychedelic state.

Despite these caveats, the findings have important implications for future research. The ability to map dynamic changes in brain networks during a psychedelic experience opens new avenues for understanding how these drugs affect consciousness and cognition. The study also provides a foundation for testing how different psychedelics might produce similar or distinct patterns of brain activity.

“One of our main focus areas is to understand if there is any unique neurophysiological or neurochemical signature that can be associated with a ‘psychedelic’ state in animal models,” Pal explained. “To that end, we have completed studies using diverse psychedelics, including subanesthetic ketamine, nitrous oxide, N’N-dimethyltryptamine, and psilocybin in the recent paper. We intend to mine these datasets for shared EEG signatures across psychedelics. In addition, we are conducting animal studies to determine the therapeutic potential of psychedelics in alleviating chronic pain (PMID: 38113836).”


The study, “Intravenous psilocybin induces dose-dependent changes in functional network organization in rat cortex,” was authored by Brian H. Silverstein, Nicholas Kolbman, Amanda Nelson, Tiecheng Liu, Peter Guzzo, Jim Gilligan, UnCheol Lee, George A. Mashour, Giancarlo Vanini, and Dinesh Pal.

LA REVUE GAUCHE - Left Comment: Search results for psychedelics

LA REVUE GAUCHE - Left Comment: Search results for LSD