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Can memories truly be read from the brain’s structure alone? A global survey of neuroscientists reveals surprising agreement on some points, and sharp divides on others, with implications for future brain preservation and emulation.

Survey: What are memories made of? A survey of neuroscientists on the structural basis of long-term memory. Image Credit: Vitalii Vodolazskyi  / Shutterstock

A recent paper published in the journal PLOS One surveyed neuroscientists to evaluate their beliefs about how memories are stored.

Recall of long-term memories enables one’s behaviors to be shaped by a lifetime’s experience. Earlier experiences must create some form of a memory trace in the brain for this to be possible.

Evidence suggests that long-lived memories are retained by relatively static and stable neurophysiological aspects. Moreover, long-term memories could be recalled even after prolonged global neuronal inactivity and depolarization, for example, during deep hypothermic circulatory arrest.

This distinction highlights that memory formation and recall rely on different processes, with formation disrupted by protein synthesis inhibition but recall largely unaffected once memories are established.

This means that the retention of long-term memories does not require ongoing global electrophysiological activity. Neuroscientists have suggested structural candidates for the physical basis of long-term memory, such as synaptogenesis, synaptic strength alterations, neuronal excitability alterations, intracellular phosphorylation, epigenetic modifications, and axonal myelination changes, as well as perineuronal net and extracellular matrix modifications.

Engrams, the neurophysiological substrates responsible for long-term memory, have been actively pursued over the past decade. Despite technological advances in the artificial manipulation of engrams and claims of a consensus that memories are stored in ensembles of synaptic connections, the extent of unanimity in the neuroscientific community about the neurophysiological basis of long-term memory is unclear.

The study and findings

In the present study, researchers surveyed neuroscientists on the structural basis of long-term memories. The survey was conducted between August and October 2024 in two cohorts of neuroscientists: 1) Computational and Systems Neuroscience (COSYNE) attendees with an abstract listed in conference booklets between 2022 and 2024, and 2) researchers with publications related to the neurophysiology of memory, i.e., engram experts.

The survey comprised 28 questions across six domains: demographics, theoretical implications of memory storage, structural basis of long-term memories, whole-brain emulation feasibility, brain preservation, and familiarity and comfort with topics discussed. A rank correlation analysis evaluated the relationships between participants’ responses to different questions. In total, 312 neuroscientists responded, with approximately three-quarters completing all mandatory sections of the survey.

They were initially asked if they believed extracting information of a specific, non-trivial long-term memory from a static synaptic connectivity map was theoretically possible. Over 45% of respondents agreed this would be possible, but 32.1% disagreed. When multiple choices were presented for what additional information might be needed for memory readout, “measurements of dynamically changing neuronal activity” was the most common choice. Other common selections included contextual information about experiences and mental states, as well as sensory input and motor output.

Further, most participants (70.5%) agreed that long-term memories are maintained by synaptic strengths and neuronal connectivity patterns. Besides, participants were asked to provide subjective probability estimates on whether memory-related information could be theoretically extracted from brains preserved using available techniques, e.g., aldehyde-stabilized cryopreservation (ASC). The median subjective probability estimate for this question was 41%. However, the distribution was bimodal, with peaks near 75% and 10%, showing that views were sharply divided rather than clustered around the median.

Beliefs about the physical basis of memory. a) Responses to the question ‘To what extent do you agree with the following statement: “Given the scientific knowledge assumed in Point A existed, it would be theoretically possible to read out the information corresponding to at least one specific non-trivial memory from a static snapshot of the structure (including biomolecules) of an organism’s entire brain.” b) Responses to the question ‘Some neuroscientists have suggested that, while molecular and subcellular details play a role, the majority of information for long-term memories is likely physically stored in the brain at the level of neuronal connectivity patterns and ensembles of synaptic strengths (e.g., Poo et al., 2016). To what extent do you agree with the following statement: “The structural basis of long-term memories primarily consists of lasting changes in neuronal connectivity and ensembles of synaptic strengths, rather than in molecular or subcellular details.” c) Participants’ views on the critical scale for memory encoding in the brain. 

In addition, the median probability estimate was 40% for the question asking whether a whole-brain emulation was theoretically possible using a preserved brain, assuming only the generic knowledge of neuronal subtypes’ electrophysiological properties. The median probability increased to 62% in a scenario where active recordings could be taken before brain preservation.

To the question asking by which year a whole-brain emulation would exist for mouse, human, or Caenorhabditis elegans, the median estimate predicted that a brain would be emulated around 2045 for C. elegans, 2065 for a mouse, and 2125 for a human. The researchers found that participants’ views did not vary by their primary approach to neuroscience, i.e., theoretical, wet-lab, or both.

Besides, participants’ education level had no significant effect. Nevertheless, there were significant relationships between the theoretical views of respondents and their practical predictions. That is, the probability estimates for extracting information on long-term memories from a preserved brain were associated with the theoretical viewpoints of participants.

These probability estimates were robustly correlated with participants’ belief in the theoretical possibility of memory extraction from static brain structure and the possibility of whole-brain emulation without dynamic recordings. However, preservation expertise, neural modeling expertise, or memory expertise did not correlate with ASC probability estimates. A small but significant negative correlation was observed with age (ρ = −0.23), indicating that older participants tended to assign lower probabilities to successful memory extraction from preserved brains.

Conclusions

In sum, the findings shed light on the beliefs of the neuroscientific community regarding the physical basis of long-term memory. Most participants endorsed that long-term memories are maintained by synaptic strengths and neuronal connectivity patterns rather than subcellular or molecular details. Nevertheless, there was no consensus on which neurophysiological scale or feature is critical for storing memory.

Some boundaries emerged, such as a general agreement that atomic-level biomolecular states are irrelevant, while subcellular structures at ~500 nm resolution would need to be included. Between these scales, however, no clear consensus was reached.

Correlation analyses further demonstrated that beliefs about whole-brain emulation and memory extraction were closely linked, showing internal consistency between theoretical stances and practical predictions.

Overall, these findings have implications for theoretical neuroscience and technological developments aimed at preserving and extracting memory-related information.

The authors also noted important limitations, including low survey response rates, the assumption of ideal preservation conditions, and the restricted cohorts studied. They further emphasized that potential ethical and societal implications, such as mental privacy and life extension via brain emulation, warrant careful consideration.

Eating disorders can affect anybody, no matter their age, gender, ethnicity, socioeconomic status or body size. Yet the myth that eating disorders are “diseases of affluence” persists, and can mean those from wealthier backgrounds are more likely to receive a diagnosis and be able to access treatment.

In fact, people who experience socioeconomic disadvantage may be more at risk of developing eating disorder symptoms, such as excessive dieting, fasting or binge eating.

A new study from the United Kingdom followed 7,824 children, roughly half male and half female, from birth to 18 years. It found those born into financial hardship were more likely than others to later experience eating disorder symptoms as teens.

This means the stereotype that eating disorders only affect the rich is simply not true. And it shows we need to better understand the risk for children from lower-income families, so we can recognise and treat their symptoms earlier.

What the study looked at

Previous research has shown eating disorders can affect people from all socioeconomic backgrounds, not just those with higher economic status. But this new study is one of the first to show deprivation in childhood could be a risk factor for eating disorder symptoms in adolescence.

This new large, long-term study collected data from thousands of people over an 18-year period to investigate the impact of social and financial hardship.

Researchers looked at parents’ education, job type and where they lived. They also examined income, which was split into five groups from low to high. These were more aspects of social studies than previous research had considered.

To assess financial hardship, mothers rated how much they struggled to afford daily expenses such as food, heating, clothing, rent and baby items. They used a scale from 0-15, with higher scores indicating greater hardship.

When the children grew up to be teenagers, researchers assessed eating disorder symptoms in all the young people across the study.

Patterns of disordered eating included excessive dieting, binge eating, vomiting or using laxatives to get rid of food, and fasting. The teens were also asked how they felt about their bodies – for example, how satisfied they were with their appearance, weight and shape.

What the study found

Eating disorder symptoms were higher in young people aged 14–18 whose parents had suffered greater financial hardship when they were babies. For patterns of disordered eating, this meant a 6% higher likelihood for every one point increase between 0 and 15 on the financial-hardship scale.

The study also found teens whose parents completed less formal education (meaning only compulsory schooling) were 80% more likely to experience disordered eating patterns than those whose parents went to university. For teens with parents in the lowest fifth and fourth income band, the risk was 34–35% higher than those in the top band of income.

These results are different to other studies on eating disorders, because they show people from low socioeconomic backgrounds have a higher chance of developing eating disorder symptoms.

The researchers suggest this difference may be because other studies only included participants with a diagnosis or who have sought help. Research has shown those experiencing financial hardship are less likely to be formally diagnosed or access treatment.

While this study is impressive in its size and results, it has a few limitations. Only around half the participants (55.9%) completed the full study, which may have affected the results.

Among those who did complete the study, some of their data was missing. This may also have influenced the findings.

The study also did not measure whether young people had a diagnosed eating disorder – only whether they had symptoms.

So, it may have captured a wider range of eating disorder experiences, including from those who wouldn’t seek formal support. But it means more research is needed to understand the link between socioeconomic status and formal diagnosis.

What does this mean?

People who are born into financial hardship may be more likely to struggle with disordered eating and body image issues in their teenage years than those who are not.

This not only debunks the stereotype that eating disorders occur only in people from affluent backgrounds, it shows disadvantage can be a risk factor.

The study sheds light on the inequalities and barriers in recognising and treating eating disorders.

Rates of people seeking help for an eating disorder are already low – and even lower among people from disadvantaged backgrounds.

The researchers suggested this could be because people from lower socioeconomic backgrounds may also believe eating disorders mainly affect people from wealthier backgrounds.

Another reason may be that lower income is linked to higher rates of obesity and being overweight, and this might limit referrals for eating disorder symptoms.

Eating disorders not associated with thinness, such as bulimia and binge eating disorder, are often less visible and go undetected.

Better education about eating disorders – in schools and for families and health-care professionals – may help us recognise and treat them earlier.

But treatment also needs to be more affordable. In Australia, people can access eating disorder treatment sessions under Medicare, but this typically still involves a gap fee which can be up to A$100 or more, depending on the service. More no- or low-cost services are needed to reach everyone who needs them.

If you have a history of an eating disorder or suspect you may have one, you can contact the Butterfly Foundation’s national helpline on 1800 334 673 (or via their online chat).

Experts have urged swift action to address the impact of plastic additives on declining sperm counts and fertility rates worldwide, The Guardian reports.

What’s happening?

Earlier this month, a sixth round of United Nations-convened talks to address the plastics crisis fell apart.

Since 2022, countries have worked to reach an agreement on a legally binding plastic treaty facilitated by the U.N. Plastic production relies on fossil fuels, and oil-producing nations, such as the United States, have resisted proposed caps on manufacturing.

As tense treaty negotiations persisted, a second, perhaps seemingly unrelated, issue remained in the news: rapidly dwindling fertility rates. 

In June, the BBC covered a report from the United Nations Population Fund, concerning “an unprecedented decline” in rates of reproduction. It focused in part on socioeconomic challenges to birth rates, but scientists say these aren’t the only contributing factors.

Shanna Swan, a professor at the Icahn School of Medicine in New York City, has been investigating links between environmental conditions and reproductive issues for years.

She told The Guardian that a notable decline in sperm counts can be attributed “largely, but not entirely … to toxins in the environment that have the ability to interfere with steroid hormones.”

With such chemicals found in many plastics, the publication noted that average sperm counts have fallen “at a rate of about 1% a year for the past 50 years,” with human fertility more broadly shown to be “diminishing at a similar rate.” 

Swan emphasized that sperm counts haven’t been dropping steadily, though — the decrease has appeared to be accelerating.

“If you looked at all of the studies going back to 1973 you [would] see a 1% per year decline. But if you look at studies published after 2000, you see an over 2% decline,” she explained.

Why is plastic pollution a concern related to fertility?

In the UNFPA’s June report on fertility rates, the organization emphasized global instability and the rising cost of living as two factors influencing voluntary reproduction. It also identified “fear for the future,” including climate concerns, to be a reason cited by 19 percent of survey respondents as figuring into family planning decisions. 

Meanwhile, environmental issues seem to be playing another role in the matter.

Swan noted that additives used to soften plastic (phthalates) and harden it (bisphenols) are known endocrine disruptors. “Phthalates lower testosterone and the bisphenols increase estrogen,” she told The Guardian. Past research from Swan and her colleagues also found that prenatal exposure to phthalates could impact the development of the male reproductive tract, leading to lower sperm counts later in life.

“When you see that total sperm count going down worldwide, what I believe is you’re seeing an important effect of early exposure to these chemicals,” she concluded.

What’s being done about it?

As a part of its fertility report, the UNFPA recommended improving equitable access to “comprehensive reproductive health services,” which could include care that takes environmental research and factors into account.

And while the U.N.’s plastic treaty efforts have yet to result in an agreement, contacting lawmakers to demand action that curbs plastic production globally is one way to address the issue. 

Consumers voting with their dollars can help too. At an individual level, using less plastic and replacing one’s most-used items with plastic-free alternatives could reduce direct exposure to endocrine-disrupting chemicals.

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