Consciousness Signature: Awareness Warnings during surgery

Anaesthesia wearing off mid-operation is not just the stuff of nightmares – it occurs in around 0.2 per cent of surgeries globally. Keeping tabs on the brain during surgery could stop this.

Indirect signs of consciousness such as changes in heart rate, blood pressure and muscle tone can be tracked during surgery but more reliable indicators are not currently available.

"It's slightly frightening that millions are given anaesthesia every year and the anaesthetist has no way of knowing with certainty that the patient is unconscious," says Tony Absalom at the University of Groningen in the Netherlands.

To look for a more concrete signature that could be monitored during surgery, Emery Brown at the Massachusetts Institute of Technology and his team attached an EEG cap with 64 electrodes to the heads of 10 adults.

They used this to measure changes in brain activity across multiple brain regions as unconsciousness was induced using a general anaesthetic.

As the volunteers lost and regained consciousness they were asked to press a button whenever they heard a click or a spoken word, allowing brain activity to be matched to different stages of wakefulness.

By constructing a montage of the activity from different parts of the brain, the team identified recognisable patterns that corresponded to different levels of consciousness, allowing them to tell when someone was waking up.

Mysterious sleep
EEG monitoring during surgery is carried out in about 2 per cent of hospitals in the UK, but only three or four electrodes are used, in a strip across the forehead.

This looks at just one brain region, however, and so can only give you a probability of unconsciousness, not a conclusive answer, says Absalom.

"You don't want something that says a patient is probably asleep. You want to know 'Are they or aren't they?'"

Using more electrodes, as Brown has done, should shore this up. Although applying more electrodes means the patient's head must be shaved and a conductive gel applied.

"The mechanisms underlying anaesthesia remain a mystery," says Ram Adapa at the University of Cambridge. But these results support the idea that anaesthesia affects the communication and synchronisation between brain regions, he says. "It is yet another piece of the jigsaw puzzle."

However, Adapa notes that it may be a while before the technique can be used in a clinical setting. EEG measurements are very sensitive to mechanical and electrical interference, he says, "and the operating room environment is unfortunately burdened by both."

Journal reference: 
Electroencephalogram signatures of loss and recovery of consciousness from propofol PNAS, 10.1073/pnas.1221180110

Chronic stress during pregnancy prevents brain benefits of motherhood

A new study in animals shows that chronic stress during pregnancy prevents brain benefits of motherhood, a finding that researchers suggest could increase understanding of postpartum depression.

Rat mothers showed an increase in brain cell connections in regions associated with learning, memory and mood.

In contrast, the brains of mother rats that were stressed twice a day throughout pregnancy did not show this increase.

The researchers were specifically interested in dendritic spines – hair-like growths on brain cells that are used to exchange information with other neurons.

Previous animal studies conducted by lead author Benedetta Leuner of Ohio State University showed that an increase of dendritic spines in new mothers’ brains was associated with improved cognitive function on a task that requires behavioral flexibility – in essence, enabling more effective multitasking.

The dendritic spines increased by about 20 percent in these brain regions in new mothers, according to her findings.

The stress in this new study negated those brain benefits of motherhood, causing the stressed rats’ brains to match brain characteristics of animals that had no reproductive or maternal experience.

The stressed rats also had less physical interaction with their babies than did unstressed rats, a behaviour observed in human mothers who experience postpartum depression.

“Animal mothers in our research that are unstressed show an increase in the number of connections between neurons. Stressed mothers don’t,” said Leuner, assistant professor of psychology and neuroscience at Ohio State.

“We think that makes the stressed mothers more vulnerable. They don’t have the capacity for brain plasticity that the unstressed mothers do, and somehow that’s contributing to their susceptibility to depression.”


Previous research has suggested that there are a number of risk factors for postpartum depression, including hormone fluctuations, prior history of mental illness and environmental factors such as smoking or low socioeconomic status.

One of the strongest predictors, however, is chronic stress during pregnancy, so Leuner sought to create an animal model that could help explain brain changes linked to postpartum depression.

“It’s devastating not only for the mother, because it affects her well-being, but previous research also has shown that children of depressed mothers have impaired cognitive and social development, may have impaired physical development, and are more likely as adults to have depression or anxiety,” she said.

“A better understanding of postpartum depression is important to help the mother but also to prevent some of the damaging effects that this disorder can have on the child.”

The researchers exposed pregnant rats to stress twice a day by limiting their mobility on some days and on other days placing them in water. For three weeks after the rats gave birth, Leuner and colleagues monitored the rats.

The animals showed classic signs of the effects of stress, including lower than normal weight gain and enlarged adrenal glands, a sign of high stress-hormone production. The mothers stressed during pregnancy also gave birth to smaller pups.

“And they were not very good mothers,” Leuner said. After separation from pups for 30 minutes, unstressed mothers would gather up their babies, put them in the nest and nurse them. Stressed mother rats left the pups scattered around, wandered around the cage and fed the babies less frequently.

The stressed mother rats also exhibited more floating than unstressed rats in a water test; animals that float rather than swim are showing depressive-like symptoms.

“These findings in rats mimic some of the symptoms that are seen in women with postpartum depression,” Leuner said.

An examination of the animals’ brains showed that the rats exposed to chronic stress did not grow the additional dendritic spines in the hippocampus and prefrontal cortex that the unstressed mother rats did.

The stressed rats’ brains more closely resembled the brains of control rats that had never been mothers.

“We don’t yet know what the exact trigger is for the increase in spines in motherhood, but we know that the increase goes away with stress,” Leuner said.

She is continuing the work by investigating whether the beneficial effects of motherhood on cognitive functions are also blocked in mothers who are exposed to pregnancy stress as well as whether hormonal factors play a role.

Kuiper Belt Researchers Study Object During A Stellar Occultation

First Team To Study A Kuiper Belt Object During A Stellar Occultation

Until now, astronomers have used telescopes to find Kuiper Belt objects (KBOs), moon-sized bodies, and obtain their spectra to determine what types of ices are on their surface.

They have also used thermal-imaging techniques to get a rough idea of the size of KBOs, but other details have been difficult to glean.

While astronomers think there are about 70,000 KBOs that are larger than 100 kilometers in diameter, the objects' relatively small size and location make it hard to study them in detail.

One method that has been has been proposed for studying KBOs is to observe one as it passes briefly in front of a bright star; such events, known as stellar occultations, have yielded useful information about other planets in the solar system.

By monitoring the changes in starlight that occur during an occultation, astronomers can determine the object's size and temperature, whether it has any companion objects and if it has an atmosphere.

The trick is to know enough about the orbit of a KBO to be able to predict its path and observe it as it passes in front of a star. This was done successfully for the first time last October when a team of 18 astronomy groups led by James Elliot, a professor of planetary astronomy in MIT's Department of Earth, Atmospheric and Planetary Sciences, observed an occultation by an object named "KBO 55636."

As Elliot and his colleagues report in a paper published to be published June 17 in Nature, the occultation provided enough data to determine the KBO's size and albedo, or how strongly it reflects light. The surface of 55636 turns out to be as reflective as snow and ice, which surprised the researchers because ancient objects in space usually have weathered, dull surfaces.

The high albedo suggests that the KBO's surface is made of reflective water-ice particles, and that would support a theory about how the KBO formed. Many researchers believe there was a collision that occurred one billion years ago between a dwarf planet in the Kuiper Belt known as Haumea and another object that caused Haumea's icy mantle to break into a dozen or so smaller bodies, including 55636.

More importantly, the research demonstrates that astronomers can predict occultations accurately enough to contribute to a new NASA mission known as the Stratospheric Observatory For Infrared Astronomy (SOFIA) that completed its first in-flight observations in May.