Physicists Overturn a 100-Year-Old Assumption on How Brains Work

The human brain contains a little over 80-odd billion neurons, each joining with other cells to create trillions of connections called synapses.

The numbers are mind-boggling, but the way each individual nerve cell contributes to the brain’s functions is still an area of contention. A new study has overturned a hundred-year-old assumption on what exactly makes a neuron ‘fire’, posing new mechanisms behind certain neurological disorders.

A team of physicists from Bar-Ilan University in Israel conducted experiments on rat neurons grown in a culture to determine exactly how a neuron responds to the signals it receives from other cells.

To understand why this is important, we need to go back to 1907 when a French neuroscientist named Louis Lapicque proposed a model to describe how the voltage of a nerve cell’s membrane increases as a current is applied.

Once reaching a certain threshold, the neuron reacts with a spike of activity, after which the membrane’s voltage resets.

What this means is a neuron won’t send a message unless it collects a strong enough signal.

Lapique’s equations weren’t the last word on the matter, not by far. But the basic principle of his integrate-and-fire model has remained relatively unchallenged in subsequent descriptions, today forming the foundation of most neuronal computational schemes.

Image credit: NICHD/Flickr

According to the researchers, the lengthy history of the idea has meant few have bothered to question whether it’s accurate.

“We reached this conclusion using a new experimental setup, but in principle these results could have been discovered using technology that has existed since the 1980s,” says lead researcher Ido Kanter.

“The belief that has been rooted in the scientific world for 100 years resulted in this delay of several decades.”

The experiments approached the question from two angles – one exploring the nature of the activity spike based on exactly where the current was applied to a neuron, the other looking at the effect multiple inputs had on a nerve’s firing.

Their results suggest the direction of a received signal can make all the difference in how a neuron responds.

A weak signal from the left arriving with a weak signal from the right won’t combine to build a voltage that kicks off a spike of activity. But a single strong signal from a particular direction can result in a message.

This potentially new way of describing what’s known as spatial summation could lead to a novel method of categorising neurons, one that sorts them based on how they compute incoming signals or how fine their resolution is, based on a particular direction.

Better yet, it could even lead to discoveries that explain certain neurological disorders.

It’s important not to throw out a century of wisdom on the topic on the back of a single study. The researchers also admit they’ve only looked at a type of nerve cell called pyramidal neurons, leaving plenty of room for future experiments.

But fine-tuning our understanding of how individual units combine to produce complex behaviours could spread into other areas of research. With neural networks inspiring future computational technology, identifying any new talents in brain cells could have some rather interesting applications.

This research was published in Scientific Reports.

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Researchers Break a 100-Year-Old Fundamental Limitation of Physics

Breaking Limits

Researchers working at the École Polytechnique Fédérale de Lausanne (EPFL) have successfully challenged a fundamental law that’s limited the physics of storing electromagnetic energy for the past 100 years. This breakthrough, which the researchers have published in the journal Science, frees up physicists and engineers to develop technologies that rely on resonant and wave-guiding systems.

First formulated in 1914, the fundamental principle known as the Lorentz reciprocity posits an inversely proportional relationship between the length of time a wave could be stored to the bandwidth (or the range of frequencies transmitted in a given signal) of resonant or wave-guiding systems. For a resonator to store energy for a longer time, it has to decrease its bandwidth. In other words, limited bandwidth translates to limited data.

The researchers managed to find a work around to the 100-year-old limitation by developing a hybrid resonant/wave-guiding system using a magno-optic material. When a magnetic field is applied, it can contain the wave for a longer period of time, while also maintaining a large bandwidth.

Opening Possibilities

The researchers broke the time-bandwidth restriction by a factor of 1,000 — but they think it may be possible that there’s no limit to how high it could go. “It was a moment of revelation when we discovered that these new structures did not feature any time-bandwidth restriction at all. These systems are unlike what we have all been accustomed to for decades, and possibly hundreds of years” said lead author Kosmas Tsakmakidis in a press release. “Their superior wave-storage capacity performance could really be an enabler for a range of exciting applications in diverse contemporary and more traditional fields of research.”

By breaking the restriction, the EPFL research will have a major impact on wide range of engineering and physics applications. “The reported breakthrough is completely fundamental – we’re giving researchers a new tool. And the number of applications is limited only by one’s imagination,” Tsakmakidis explained.

These applications could also extend to telecommunications, optical detection systems, and broadband energy harvesting, the press release noted. Essentially, any technology that uses waves to store information now has access to a wider bandwidth. That could be anything from on-chip spectroscopy, light harvesting and energy storage using broadband to broadband optical camouflaging — such as an invisibility cloak.

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100-Year-Old Drug May Be the Key to Treating Autism

Old Drug, New Tricks

A small clinical trial from the University of California, San Diego, has just yielded some promising results for those living with autism spectrum disorder (ASD). The results indicate that suramin, a 100-year-old drug used to treat African sleeping sickness, can measurably, albeit transiently, improve ASD symptoms in children.

This has led the research team to conclude that ASD in many children may be caused by a treatable metabolic syndrome and that, for some people with ASD, the right treatment can improve symptoms since they are not necessarily permanent.

*4* 100-Year-Old Drug May Be the Key to Treating Autism
Image Credit: Abhijit Bhaduri / Flickr

ASD is just that — a spectrum, and many children fall somewhere on that spectrum. According to the World Health Organization, about one in 160 children worldwide have ASD, although the CDC estimates that number to be one in 68. While it is not entirely clear whether the incidence of ASD is increasing, or detection of ASD is changing, or some other mechanism is at work making the numbers grow, there is no doubt that many people are affected.

The UCSD team is now focusing on metabolism — the shared language of the brain, immune system, and gut which allows the three linked systems to communicate. In people with ASD, each of these systems works differently, and the communication between them is altered.

The researchers chose to test suramin because it inhibits purinergic signaling, a cell communications process that takes place in metabolism. Within seven days, all five of the children treated with suramin showed a steady improvement of symptoms, with no change at all shown in the placebo group.

New Approaches To ASD

These results mark the first time any drug has shown the potential to actually alter symptoms of ASD. Of course this is a small first trail, and the treatment may never be available depending on further research outcomes. Even so, these results are likely to prompt a major shift in the way we think about autism.

If the researchers are right, abnormally persistent cell danger response (CDR) is what’s producing the metabolic syndrome causing ASD. Both environment and genes are factors in the CDR, so it’s possible that genetic causes alone might produce the metabolic syndrome and ASD. However, if a metabolic syndrome is what’s behind ASD symptoms, it can be treated, even though the genes can’t be.

This research also provides the first real unifying theory for the root cause of ASD. The lack of such a theory has been a huge factor in pharmacologic failures in treating aspects ASD. Treatments weren’t targeting the aspect of autism that could lower people’s quality of life and were sometimes worse than symptoms.

However, if this unifying theory is right that CDR and problems in purinergic signaling play an important role in some forms of ASD, then doctors should be able to treat some symptoms of ASD — such as difficulties with verbal communication, fear of changes in routine, and social anxiety — without suppressing the traits that sometimes make people with ASD exceptional.

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