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The technique, called non-invasive electrical brain stimulation, involves applying an electrical current to the surface of a patient’s head to stimulate brain cells, altering the patient’s brain activity. It is being trialled for a range of neurological problems including recovery from stroke, traumatic brain injury, dementia, and depression, but research to date has found the effects to be inconsistent

Now, a team led by researchers at Imperial College London has shed more light on why these inconsistencies occur and may provide physical evidence for why some patients respond better than others — because of the fine structure of their brain tissue. The new research suggests it may be possible to target the therapy to those patients most likely to benefit.

They found that differences in the makeup of the brain’s white matter — the tissue deep in the brain and rich in the branching ‘tails’ of nerve cells — were key. The research revealed that those who had more connectivity in the regions being stimulated were more likely to respond better to the treatment.

According to the team, the findings, published in the journal Brain, could help to personalise the non-invasive electrical brain stimulation, targeting the treatment to patients who are most likely to gain clinical benefits.

Dr Lucia Li, a clinical lecturer in neurology in the Department of Brain Sciences at Imperial College London, and lead author of the study, said: “With all the current buzz around brain stimulation for altering brain activity, it’s important to understand who will benefit most from this technique in the clinic.

“Problems with white matter structure are a feature of a range of different neurological conditions. Our study is a step towards more personalised use of brain stimulation, which will improve the outcomes using this technique, as well as reduce the number of people treated un-necessarily.”

In the study, researchers looked at 24 healthy patients and 35 patients recovering from a moderate or severe traumatic brain injury (TBI). Participants performed a task inside an MRI scanner (see ‘The Stop Signal Task’ in notes to editors) while receiving small amounts of electrical current through electrodes on the surface of the scalp or a placebo. They were unable to tell whether they were receiving brain stimulation or not.

They found that healthy participants who received brain stimulation performed better in the task than when they didn’t receive the treatment. For patient with TBI, task performance in response to stimulation varied widely.

However, when they analysed MRI scans, they found that those participants with highly-connected white matter in the brain region being stimulated responded best to the treatment, and those who had damaged or less-connected regions of white matter showed less improvement.

They also found that brain stimulation could partially reverse some of the abnormalities in brain activity caused by TBI.

The team cautions that while more work is needed to confirm the findings, it could mean brain stimulation might prove a useful treatment approach for other neurological conditions with abnormal brain activity as a feature, such as dementia.

“We found that people with stronger white matter connections in their brain had better improvement with stimulation,” Dr Li explained. “This might be an important reason why previous studies have found that some people benefit from stimulation, whilst others don’t and means we can start using brain stimulation in a more personalised way.”

According to the researchers, the study is limited in that in that they only investigated one type of cognitive behaviour and would need to be replicated in other types of behaviour to show if the findings apply more generally. In addition, they only stimulated one region of the brain, so they don’t know whether the effects are specific to this region, or whether other regions can be stimulated.

Dr Li explains the team will now focus on larger studies with more participants to investigate what other factors influence someone’s response to brain stimulation. They will also apply the technique to other conditions with abnormalities in brain activity to see if they can alter activity and improve brain function.

The work was supported by the Wellcome Trust and the National Institute for Health Research. Patients were predominantly recruited from St Mary’s Hospital (Imperial College Healthcare NHS Trust) and imaged at the Imperial College Clinical Imaging Facility.

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Researchers at the University of Cambridge, who led the study published today in the journal Physiological Reports, say the findings reinforce the importance of an active lifestyle when planning pregnancy.

In the UK, more than a half of all women of reproductive age and almost a third of pregnant women are overweight or obese. This is particularly concerning, as being overweight or obese during pregnancy increases the risk of complications in the mother, such as gestational diabetes, and predisposes both her and her infant to develop metabolic diseases such as type 2 diabetes in the years after pregnancy.

Exercise is known to improve how the body manages blood sugar levels and thereby reduce the risk of type-2 diabetes and metabolic syndrome in non-pregnant women. It also has positive effects prior to and during pregnancy, with beneficial outcomes for both mother and her child, preventing excessive gestational weight gain and the development of gestational diabetes, and the need for insulin use in women who have already developed gestational diabetes. However, little is known about the changes that exercise causes to the tissues of obese pregnant mother.

To answer this questions, researchers at the University of Cambridge fed mice a sugary, high fat diet such that they become obese and then the obese mice were exercised. The mice exercised on a treadmill for 20 minutes a day for at least a week before their pregnancy and then for 12.5 minutes a day until day 17 of the pregnancy (pregnancy lasts for around 20 days in mice).

Mice are a useful model for studying human disease as their biology and physiology have a number of important characteristics in common with those of humans, including showing metabolic changes with obesity/obesity-causing diets and in the female body during pregnancy.

The researchers found that the beneficial effects on metabolic health in obese mothers related to changes in how molecules and cells communicate in maternal tissues during pregnancy.

“A moderate level of exercise immediately before and then during pregnancy leads to important changes in different tissues of the obese mother, effectively making the tissues more like those seen in non-obese mothers,” says Dr Amanda Sferruzzi-Perri, a Royal Society Dorothy Hodgkin Research Fellow from the Centre for Trophoblast Research in the Department of Physiology, Development and Neuroscience at the University of Cambridge, who co-led the study.

“We believe these changes may explain how exercise improves the metabolism of the obese mother during pregnancy and, in turn, may prevent her babies from developing early signs of type 2 diabetes after birth.”

The key organs of the mother that were affected by exercise were:

• white adipose tissue — the fatty tissue that stores lipids and can be found in different parts around the body, including beneath the skin and around internal organs;
• skeletal muscle — muscle tissue that uses glucose and fats for contraction and movement;
• the liver — the organ that stores, as well as syntheses lipids and glucose.

Exercise affected key signalling pathways — the ways that molecules and cells within tissue communicate — involved in responding to insulin (the hormone that stimulates glucose uptake by white adipose tissue and skeletal muscle), in storage and breakdown of lipids (fats found in the blood and tissue) and in growth and the synthesis of proteins.

White adipose tissue showed the greatest number of changes in response to exercise in the obese pregnant mouse, being restored to a state similar to that seen in the tissue of non-obese mothers. This suggests that insulin resistance of the mother’s white adipose tissue may be the cause of poor glucose-insulin handling in obese pregnancies. The findings are different to that seen in non-pregnant animals, whereby exercise typically affects insulin signalling in the skeletal muscle.

In addition, the team’s previous work showed that exercise improves sensitivity to insulin and glucose handling throughout the whole body in the obese mother. It also prevents the development of insulin resistance in the offspring of obese mothers after birth. Low insulin sensitivity/insulin resistance requires larger amounts of insulin to control blood glucose levels.

“Our findings reinforce the importance of having an active lifestyle and eating a healthy balanced diet when planning pregnancy and throughout for both the mother and her developing child,” says co-lead Professor Susan Ozanne from the Wellcome Trust-Medical Research Council Institute of Metabolic Science at the University of Cambridge.

“This is can be important in helping to reduce the risk of adverse health problems in the mother and of later health problems for her child.”

However, there exists a strange anomaly in the North Pacific Subtropical Gyre ecosystem that has puzzled scientists for years. In this region that occupies the Pacific Ocean between China and the United States, the chemistry changes periodically. There’s a particularly notable fluctuation in the levels of phosphorus and iron, which affects the overall nutrient composition and ultimately impacts biological productivity.

In a new study published in the Proceedings of the National Academy of Sciences, a group of researchers uncovered the reason behind these variations in the North Pacific Subtropical Gyre ecosystem. The group includes Matthew Church, a microbial ecologist with the University of Montana’s Flathead Lake Biological Station, as well as Oregon State University’s Ricardo Letelier and the University of Hawaii’s David Karl, among others.

“Variations in ocean climate appear to regulate iron supply, altering the types of plankton growing in these waters, which ultimately controls ocean nutrient concentrations,” Church said. “My laboratory has worked on questions related to the role of plankton in controlling ocean nutrient availability for many years, and this study places much of that work in context. As a result of sustained, long-term observations, our work confirms how tightly coupled plankton biology is to the supply of nutrients, specifically iron, delivered from the atmosphere.”

Using three decades of observational data from Station ALOHA, a six-mile area in the Pacific Ocean north of Hawaii dedicated to oceanographic research, the team discovered that the periodic shift in iron levels result from iron input from Asian dust, accounting for the chemical variances and providing varying amounts of nutrients to sustain life.

The key to the variance is the Pacific Decadal Oscillation, an ocean-atmosphere relationship that varies between weak and strong phases of atmospheric pressure in the northeast Pacific Ocean.

In years when the low pressure weakens in the northeast Pacific, winds from Asia become stronger and move in a more southern direction. This brings more dust from the Asian continent, “fertilizing” the ocean surrounding Station ALOHA. When the pressure strengthens, the opposite occurs.

The supply of nutrients is a fundamental regulator of ocean productivity, and phosphorus and iron are key components for life. Typically, the ocean’s upper water column is fertilized by nutrient-rich water mixing up from the deep. This is a difficult process in the North Pacific Subtropical Gyre ecosystem because the waters are very stratified and little mixing actually takes place.

When strong Asian winds bring in significant amounts of iron, organisms are allowed to grow and use phosphorus in the upper layers of the ocean. When Asian winds weaken and iron input is reduced, organisms are forced to return to a deep-water-mixing nutrient delivery system. This creates the periodic ebb and flow of iron and phosphorus levels in the North Pacific Gyre.

Church said the findings from this study emphasize the critical need to include both atmospheric and ocean circulation variability when forecasting how climate change might impact ocean ecosystems.

“It reaffirms the need to think about how tightly connected plankton biology is to changes in climate and ultimately also to changes in land use, which can directly impact dust supply to the sea,” he said.

As Earth’s temperature continues to warm, researchers expect to see long-term changes in wind patterns across the North Pacific. The evolution of land use and pollution driven by human activity in Asia also will affect the sources and magnitude of iron and other nutrients carried by wind across the ocean.

Further research is needed to better understand how these changes ultimately will impact ecosystems in this ocean region, as well as others around the world.