London: British neuroscientists have identified the brain network system that causes us to stumble and stall, which may have a disastrous effect on our performance.
Scientists at the University of Sussex’s Sackler Centre and Brighton and Sussex Medical School were able to pinpoint the brain area that causes the performance mishaps during an experiment using functional magnetic resonance neuroimaging (fMRI).
Previous study has shown that people tend to exert more force when they know they are being watched. For example, pianists unconsciously press keys harder when they play in front of an audience compared to when playing alone.
In the new study, participants’ brain activity was monitored while carrying out a task that required them to exert a precise amount of force when gripping an object.
During the experiment, they viewed video footage of two people whom they believed were evaluating their performance. They then repeated the task while viewing video footage of two people who appeared to be evaluating the performance of someone else.
Participants reported that they felt more anxious when they believed they were being observed. Under this condition, they gripped the object harder without realising it.
Scan results showed that an area of the brain that helps us to control our fine sensorimotor functions – the inferior parietal cortex (IPC) – became deactivated when people felt they were being observed.
In fact, this part of the brain works with another region – the posterior superior temporal sulcus (pSTS) – to form what neuroscientists refer to as the action-observation network (AON). The AON is involved in “mentalisation” processes by which we infer what another person is thinking, based on his/her facial expressions and direction of gaze.
The pSTS conveys this information to the IPC, which then generates appropriate motor actions. If we feel our observer wants us to do well, we will perform well. But if we pick up negative cues, our IPC is deactivated and our performance falls apart.
The study results were published recently in the journal Scientific Reports. (IANS)
Microbes may be helping stir up anxiety and depression in obese people, if results from a new mouse study hold true in humans.
The authors link the effects to how the brain responds to insulin, the hormone that regulates sugar levels in the blood.
The research raises questions about whether changing gut microbes, or changing diet, could help treat these conditions.
Mood, microbes and metabolism
Obesity triggers changes in metabolism — for example, making liver, muscle, fat and other tissues less responsive to insulin. Left untreated, these changes can lead to diabetes.
Obese people also have higher rates of anxiety and depression.
“One could say, ‘Maybe that’s just because they’re obese,’ ” said Harvard Medical School diabetes researcher Ronald Kahn, “but others could say, ‘Maybe there’s a metabolic link.’ ”
“And we asked the question, ‘Maybe the metabolic link is at least partly fueled by the microbiome,’ ” the community of microbes living in a person’s gut, he added.
Those microbes change with diet, and Kahn said different microbes might respond differently to the foods we eat.
To test the theory, Kahn and colleagues fed mice a high-fat diet and studied their behavior as the animals became obese.
They used common tests to gauge anxious and depressed behavior in rodents — for example, how much time the animals spent hiding in a dark box versus exploring a brightly lit area. The more anxious the mouse, the less time it will spend in the light.
Obese mice spent about 25 percent less time in the light than animals on a normal diet, and they scored higher on the other anxiety and depression tests, too.
Return to normal
But those differences disappeared when obese mice were given antibiotics, even though their weight didn’t change much.
“That really says there’s probably something about the microbiome,” Kahn said.
The researchers then tested how the animals’ microbiomes affected mice raised in a sterile environment with no microbes of their own.
Bacteria from obese rodents made these germ-free mice more anxious than microbes from normal mice.
But when germ-free mice got microbes from obese animals that had been given antibiotics, they behaved like normal mice.
To see what parts of the brain might be responsible for the effects, the researchers focused on two regions involved in metabolism and responses to rewards. They found these regions were less responsive to insulin in the obese mice compared with normal-weight animals.
Again, antibiotics returned those responses to normal.
“It was actually quite a surprise,” Kahn said. “Even though we had seen some effects on metabolism in the rest of the body, I was very surprised how dramatic and how clear the effects were also on the brain and on behavior.”
Into the unknown
That doesn’t mean antibiotics are the cure for depression, Kahn warned. The drugs kill good and bad microbes indiscriminately, and taking the medication unnecessarily can contribute to the rising threat of antibiotic resistance.
Also, what happens in mice does not necessarily happen in humans, he added, or it may happen for only some people. So far, there is not much evidence that probiotics help anxious people.
“The difficulty is, both of these things — depression and obesity — are complicated things that have multiple, multiple factors influencing them,” said mental health researcher Gregory Simon at Kaiser Permanente Washington Health Research Institute, who was not part of the study.
Microbes are likely just one factor, along with environment, genetics, social influences and more, Simon added.
But Kahn said his group’s research raised interesting questions about how food affects our behavior.
“I think now we can get some idea that there are a lot of things that are being metabolized by gut bacteria that could affect brain function,” he said.
And he said there might be ways to change brain function by changing those bacteria, by eating helpful microbes or by eating foods that sustain them.