Anxious? Activate Your Anterior Cingulate Cortex With a Little Meditation

Scientists, like Buddhist monks and Zen masters, have known for years that meditation can reduce anxiety, but not how. Scientists at Wake Forest Baptist Medical Center, however, have succeeded in identifying the brain functions involved.

“Although we’ve known that meditation can reduce anxiety, we hadn’t identified the specific brain mechanisms involved in relieving anxiety in healthy individuals,” said Fadel Zeidan, Ph.D., postdoctoral research fellow in neurobiology and anatomy at Wake Forest Baptist and lead author of the study. “In this study, we were able to see which areas of the brain were activated and which were deactivated during meditation-related anxiety relief.”

The study is published in the current edition of the journal Social Cognitive and Affective Neuroscience.

For the study, 15 healthy volunteers with normal levels of everyday anxiety were recruited for the study. These individuals had no previous meditation experience or anxiety disorders. All subjects participated in four 20-minute classes to learn a technique known as mindfulness meditation. In this form of meditation, people are taught to focus on breath and body sensations and to non-judgmentally evaluate distracting thoughts and emotions.

Both before and after meditation training, the study participants’ brain activity was examined using a special type of imaging – arterial spin labeling magnetic resonance imaging – that is very effective at imaging brain processes, such as meditation. In addition, anxiety reports were measured before and after brain scanning.

The majority of study participants reported decreases in anxiety. Researchers found that meditation reduced anxiety ratings by as much as 39 percent.

“This showed that just a few minutes of mindfulness meditation can help reduce normal everyday anxiety,” Zeidan said.

The study revealed that meditation-related anxiety relief is associated with activation of the anterior cingulate cortex and ventromedial prefrontal cortex, areas of the brain involved with executive-level function. During meditation, there was more activity in the ventromedial prefrontal cortex, the area of the brain that controls worrying. In addition, when activity increased in the anterior cingulate cortex – the area that governs thinking and emotion – anxiety decreased.

“Mindfulness is premised on sustaining attention in the present moment and controlling the way we react to daily thoughts and feelings,” Zeidan said. “Interestingly, the present findings reveal that the brain regions associated with meditation-related anxiety relief are remarkably consistent with the principles of being mindful.”

Research at other institutions has shown that meditation can significantly reduce anxiety in patients with generalized anxiety and depression disorders. The results of this neuroimaging experiment complement that body of knowledge by showing the brain mechanisms associated with meditation-related anxiety relief in healthy people, he said.

Fear: A Justified Response or Faulty Wiring?

Fear is one of the most primal feelings known to man and beast. As we develop in society and learn, fear is hard coded into our neural circuitry through the amygdala, a small, almond-shaped nuclei of neurons within the medial temporal lobe of the brain. For psychologists and neurologists, the amygdala is a particularly interesting region of the brain because it plays a role in emotional learning and can have profound effects on human and animal behavior.

On June 3, 2013, a new article studying amygdala activity in human beings will be published as part of JoVE Behavior, a new section of the video journal that focuses on the behavioral sciences. The technique, developed by Dr. Fred Helmstetter and his research group at the University of Wisconsin-Milwaukee, studies how the brain responds to anticipated painful stimuli, in this case an electric shock, in volunteer test subjects.

“We’re interested in how the brain reacts to stimuli in the environment and how it changes when we form a memory of what we experience.” Dr. Helmstetter explains. “The amygdala is a part of the brain that’s important for the way we determine what is dangerous and what is safe around us and how we react to threat.  This experiment is novel in that we are able to look at activity in the amygdala on a very detailed time scale while it responds to human faces.“

The technique takes advantage of two neuroimaging techniques: magnetic resonance imaging and magnetoencephalography. Magnetic resonance imaging (MRI) is a method where a test subject’s brain can be imaged in high resolution while the test subject is immobilized, creating a map of the brain. Once this map has been obtained, magnetoencephalography (MEG) is used to record the magnetic fields created by the electrical activity within the brain. When the test subject is shocked, or anticipates a shock, amygdala activity is picked up by the MEG and mapped to the MRI computer model.

As an emotional control center in the brain, the amygdala serves as a key component in a line of neurological structures that identify and respond to perceived threat. Dr. Helmstetter tells us, “There is good evidence to suggest that anxiety disorders and other psychopathology might be directly related to altered functioning of the amygdala. Prior work with other non-invasive imaging modalities supports this idea but has only been able to average the results of neural activity over several seconds which results in a poor picture of how neurons react to a stimulus over time. This work represents a significant improvement and will allow new questions to be answered.”

The article is part of the launch of JoVE Behavior, the eighth section of JoVE. Founded in 2006, JoVE has rapidly expanded its scope from general biology to many disciplines by visualizing experimentation. Director of Content Aaron Kolski-Andreaco, PhD explains that, “By dedicating a section to behavior, JoVE has provided a platform for researchers to visualize experiments aimed at answering questions about how we think, feel, and communicate with one another.   Emphasizing this area of science is the next logical step for our journal, as the multidisciplinary study of behavior is enabled by technological advancements in physics, chemistry, and the life sciences - areas JoVE has already covered.”

Neuronal regeneration and the two-part design of nerves

Researchers at the University of Michigan have evidence that a single gene controls both halves of nerve cells, and their research demonstrates the need to consider that design in the development of new treatments for regeneration of nerve cells.

A paper published online in PLOS Biology by U-M Life Sciences Institute faculty member Bing Ye and colleagues shows that manipulating genes of the fruit fly Drosophila to promote the growth of one part of the neuron simultaneously stunts the growth of the other part.

Understanding this bimodal nature of neurons is important for researchers developing therapies for spinal cord injury, neurodegeneration and other nervous system diseases, Ye said.

Nerve cells look strikingly like trees, with a crown of “branches” converging at a “trunk.” The branches, called dendrites, input information from other neurons into the nerve cell. The trunk, or axon, transmits the signal to the next cell.

"If you want to regenerate an axon to repair an injury, you have to take care of the other end, too," said Ye, assistant professor in the Department of Cell and Developmental Biology at the U-M Medical School.

The separation of the nerve cell into these two parts is so fundamental to neuroscience that it’s known as the “neuron doctrine,” but how exactly neurons create, maintain and regulate these two separate parts and functions is still largely unknown.

While the body is growing, the neuronal network grows rapidly. But nerve cells don’t divide and replicate like other cells in the body (instead, a specific type of stem cell creates them). Adult nerve cells appear to no longer have the drive to grow, so the loss of neurons due to injury or neurodegeneration can be permanent.

Ye’s paper highlights the bimodal nature of neurons by explaining how a kinase that promotes axon growth surprisingly has the opposite effect of impeding dendrite growth of the same cell.

In the quest to understand the fundamentals of nerve cell growth in order to stimulate regrowth after injury, scientists have identified the genes responsible for axon growth and were able to induce dramatic growth of the long “trunk” of the cell, but less attention has been given to dendrites.

There are technical reasons that studying axons is easier than studying dendrites: The bundle of axons in a nerve is easier to track under the microscope, but to get an image of dendrites would require labeling single neurons.

Ye’s lab circumvented that obstacle by using Drosophila as a model. Using this simple model of the nervous system, the scientists were able to reliably label both axons and dendrites of single neurons and see what happened to nerve cells with various mutations of genes that are shared between the flies and humans.

One of the genes shared by Drosophila and people is the one that makes a protein called Dual Lucine Zipper Kinase, or DLK. As described previously by other groups, DLK is a product of the gene responsible for axon growth. Cells with more of the protein had very long axons, and those without the gene or protein had no regeneration after nerve injury. The DLK kinase seemed a promising target for therapies to regenerate nerve cells.

However, Ye’s lab found that the kinase had the opposite effect on the dendrites: Lots of DLK leads to diminished dendrites.

"This in vivo evidence of bimodal control of neuronal growth calls attention to the need to look at the other side of a neuron in terms of developing new therapies," Ye said. "If we use this kinase, DLK, as a drug target for axon growth, we’ll have to figure out a way to block its effect on dendrites."

Heart Health Matters to Your Brain

People suffering from type 2 diabetes and cardiovascular disease (CVD) are at an increased risk of cognitive decline, according to a new study from Wake Forest Baptist Medical Center.

Lead author Christina E. Hugenschmidt, Ph.D., an instructor of gerontology and geriatric medicine at Wake Forest Baptist, said the results from the Diabetes Heart Study-Mind (DHS-Mind) suggest that CVD is playing a role in cognition problems before it is clinically apparent in patients. The research appears online ahead of print in the Journal of Diabetes and Its Complications.

 ”There has been a lot of research looking at the links between type 2 diabetes and increased risk for dementia, but this is the first study to look specifically at subclinical CVD and the role it plays,” Hugenschmidt said. “Our research shows that CVD risk caused by diabetes even before it’s at a clinically treatable level might be bad for your brain.

"The results imply that additional CVD factors, especially calcified plaque and vascular status, and not diabetes status alone, are major contributors to type 2 diabetes related cognitive decline."

Hugenschmidt said DHS-Mind is a follow-up study to the Diabetes Heart Study (DHS), which examined relationships between cognitive function, vascular calcified plaque and other major diabetes risk factors associated with cognition. The DHS investigated CVD in siblings with a high incidence and prevalence of type 2 diabetes, where extensive measurements of CVD risk factors were obtained during exams that occurred from 1998 to 2006.

The study was supported by the National Institutes of Health through NINDS R01NS058700-02S109 and NIDDK 1F32DK083214-01.

The DHS-Mind study added cognitive testing to existing measures with the express purpose of exploring the relationships between measures of atherosclerosis and cognition in a population heavily affected by diabetes, a novel approach given that previous studies have focused on diabetes and cognition in the context of clinically evident CVD, Hugenschmidt said. The researchers followed up with as many of the original 1,443 DHS study participants as possible who had cardiovascular measures. Of that 516 total, 422 were affected with type 2 diabetes and 94 were unaffected.

Hugenschmidt said the researchers ran a battery of cognitive testing that looked at different kinds of thinking like memory and processing speed, as well as executive function, which is a set of mental skills coordinated in the brain’s frontal lobe that includes stop and think processes like managing time and attention, planning and organizing. She said that being able to look at data where the comparison group was  siblings, some of whom had a high level of CVD themselves, made the results more clinically relevant because the participants shared the same environmental and genetic background.

"We still saw a difference between these two groups. Even compared to their own siblings who were not disease free, those with diabetes and subclinical cardiovascular disease had a higher risk of cognitive dysfunction," Hugenschmidt said.

CVD explains a lot of the cognitive problems that people with diabetes experience, Hugenschmidt said. “One possibility is that your brain requires a really steady blood flow and it’s possible that the cardiovascular disease that accompanies diabetes might be the main driver behind the cognitive deficits that we see.”

Hugenschmidt said the takeaway for clinicians is to take CVD risk factors into consideration when they’re treating patients with type 2 diabetes patients because even at borderline clinical levels, it might have long-term implications for peoples’ mental, cognitive health.

Blood Vessels in the Eye Linked With IQ, Cognitive Function

The width of blood vessels in the retina, located at the back of the eye, may indicate brain health years before the onset of dementia and other deficits, according to a new study published in Psychological Science, a journal of the Association for Psychological Science.

Research shows that younger people who score low on intelligence tests, such as IQ, tend to be at higher risk for poorer health and shorter lifespan, but factors like socioeconomic status and health behaviors don’t fully account for the relationship. Psychological scientist Idan Shalev of Duke University and colleagues wondered whether intelligence might serve as a marker indicating the health of the brain, and specifically the health of the system of blood vessels that provides oxygen and nutrients to the brain.

To investigate the potential link between intelligence and brain health, the researchers borrowed a technology from a somewhat unexpected domain: ophthalmology.

Shalev and colleagues used digital retinal imaging, a relatively new and noninvasive method, to gain a window onto vascular conditions in the brain by looking at the small blood vessels of the retina, located at the back of the eye. Retinal blood vessels share similar size, structure, and function with blood vessels in the brain and can provide a way of examining brain health in living humans.

The researchers examined data from participants taking part in the Dunedin Multidisciplinary Health and Development Study, a longitudinal investigation of health and behavior in over 1000 people born between April 1972 and March 1973 in Dunedin, New Zealand.

The results were intriguing.

Having wider retinal venules was linked with lower IQ scores at age 38, even after the researchers accounted for various health, lifestyle, and environmental risk factors that might have played a role.

Individuals who had wider retinal venules showed evidence of general cognitive deficits, with lower scores on numerous measures of neurospsychological functioning, including verbal comprehension, perceptual reasoning, working memory, and executive function.

Surprisingly, the data revealed that people who had wider venules at age 38 also had lower IQ in childhood, a full 25 years earlier.

It’s “remarkable that venular caliber in the eye is related, however modestly, to mental test scores of individuals in their 30s, and even to IQ scores in childhood,” the researchers observe.

The findings suggest that the processes linking vascular health and cognitive functioning begin much earlier than previously assumed, years before the onset of dementia and other age-related declines in brain functioning.

“Digital retinal imaging is a tool that is being used today mainly by eye doctors to study diseases of the eye,” Shalev notes. “But our initial findings indicate that it may be a useful investigative tool for psychological scientists who want to study the link between intelligence and health across the lifespan.”

The current study doesn’t address the specific mechanisms that drive the relationship between retinal vessels and cognitive functioning, but the researchers surmise that it may have to do with oxygen supply to the brain.

“Increasing knowledge about retinal vessels may enable scientists to develop better diagnosis and treatments to increase the levels of oxygen into the brain and by that, to prevent age-related worsening of cognitive abilities,” they conclude.

Positive Feedback: Researchers have found a new role for mTOR in autism-related disorders

Researchers have found a novel role for a protein that has been implicated in an autism-related disorder known as tuberous sclerosis complex (TSC).

The disease, which affects 1 in about 8,000 children, manifests itself in the form of mental retardation in addition to severe epileptic episodes. The disease is caused by mutations in two tumor-suppressing proteins, TSC1 and TSC2.

“Kids with this condition have benign tumors that grow all over the body,” said Bernardo Sabatini, the Takeda Professor of Neurobiology at Harvard Medical School and senior author of the study, “but we wanted to know what happened in the brain.”

The researchers found that when mutations in TSC1 and TSC2 adversely affected a third protein, mTOR, this mutation increased brain activity, which can result in epileptic seizures.

The findings were published in the May 8 issue of Neuron.

A protein kinase, mTOR is responsible for controlling cell growth in many parts of the body and has been widely implicated in epilepsy and autism. TSC1 and TSC2 normally repress the activity of mTOR to keep cell growth in check. In the case of TSC, there are mutations in TSC1 or TSC2, and mTOR’s ability to promote cell growth goes unchecked, resulting in tumors in regularly dividing cells.

“But neurons don’t divide,” said Sabatini. “So it was important to note the changes in these non-dividing cells.”  

The researchers hypothesized that mTOR’s function in the brain related to homeostasis, the brain’s ability to maintain a controlled level of electrical activity. When there’s a lot of electrical activity, a negative feedback system switches on to suppress activity. Conversely, when levels are too low, other positive feedback pathways are engaged that bring the activity level back up.

“We went into this study with the specific hypothesis that mTOR would be part of the homeostatic loop in the brain,” explained Sabatini.  

In the case of TSC patients, they thought that mTOR was incapable of maintaining homeostasis and kept adding to the level of electrical activity, leading to seizures. 

“But we were wrong,” he added.

“What we actually found was that mTOR is part of a positive feedback pathway,” said Helen Bateup, HMS research fellow in neurobiology and first author on the study. “When a cell is active, mTOR gets turned on more frequently and makes the cell even more active by reducing the amount of inhibition that the neuron receives.”

In cells where TSC proteins are mutated, this positive feedback gets out of control, and the neuronal circuit remains overactive despite all the pathways that normally shut down activity being turned on.

“It’s like the circuit is trying to keep itself quiet, but it can’t,” said Sabatini. “The out-of-control mTOR causes some cells to loss all inhibition, something that can’t be compensated for by turning down excitation.”                                        

The researchers think this key difference in how mTOR operates, in working to promote electrical activity, is important for the disease because patients end up with high levels of dysfunctional mTOR that makes for highly active circuits prone to epileptic fits. Furthermore, “we know that once a person has one seizure, they’re much more likely to have more, a concept known as kindling,” said Sabatini.

These findings are among the first to show that contrary to scientific consensus, mTOR does not play a part in everything.

“We have shown that one of the few things that mTOR does not seem to partake in is this negative feedback pathway,” said Sabatini.

Working in both in vitro and in vivo mouse models, the researchers think the next step would be tease out the molecular pathway of mTOR’s involvement in this positive feedback loop. “It’s also important to compare how this pathway works in normal brains versus a diseased model,” added Bateup.

“A huge challenge when studying the brain is that there are so many feedback pathways that a mutation in one gene can result in a hundred other secondary changes,” said Sabatini.

Rapamycin, a drug currently used to prevent organ rejection following transplants, targets mTOR and brings activity levels back to normal.

“We could use the drug to restore this excitatory-inhibitory balance in the brain,” said Bateup. “A lot of drugs that treat epilepsy try to make inhibition more powerful but given that the primary problem here is that a group of cells has lost inhibition, that approach won’t work,” she added. “What we might need is to target the excitation side. Or find ways of changing the biochemistry of the cells to make inhibitory synapses again.” 

“For this disease, this is the right time to start looking at human cells,” said Sabatini. “We have really good data from the mouse model and it would be a really nice test to see if the mouse model is really predictive of human disorder and if it’s worth being continued.” 

Researchers focus on a brain protein and an antibiotic to block cocaine craving

A new study conducted by a team of Indiana University neuroscientists demonstrates that GLT1, a protein that clears glutamate from the brain, plays a critical role in the craving for cocaine that develops after only several days of cocaine use.

The study, appearing in The Journal of Neuroscience, showed that when rats taking large doses of cocaine are withdrawn from the drug, the production of GLT1 in the nucleus accumbens, a region of the brain implicated in motivation, begins to decrease. But if the rats receive ceftriaxone, an antibiotic used to treat meningitis, GLT1 production increases during the withdrawal period and decreases cocaine craving.

George Rebec, professor in the Department of Psychological and Brain Sciences, said drug craving depends on the release of glutamate, a neurotransmitter involved in motivated behavior. Glutamate is released in response to the cues associated with drug taking, so when addicts are exposed to these cues, their drug craving increases even if they have been away from the drug for some time.

The same behavior can be modeled in rats. When rats, who self-administer cocaine by pressing a lever that delivers the cocaine into their bodies, are withdrawn from the drug for several weeks, their craving returns if they are exposed to the cues that accompanied drug delivery in the past; in this case, a tone and light. But if the rats are treated with ceftriaxone during withdrawal, they no longer seek cocaine when the cues are presented.

Ceftriaxone appears to block craving by reversing the decrease in GLT1 caused by repeated exposure to cocaine. In fact, ceftriaxone increases GLT1, which allows glutamate to be cleared quickly from the brain. The Rebec research group localized this effect to the nucleus accumbens by showing that if GLT1 was blocked in this brain region even after ceftriaxone treatment, the rats would relapse.

While an earlier paper of Rebec’s group showed the effects of ceftriaxone on cocaine craving, the new paper was the first to localize the effects of ceftriaxone to the nucleus accumbens and was the first to show that ceftriaxone works after long withdrawal periods.

"The idea is that increasing GLT1 will prevent relapse. If we block GLT1, the ceftriaxone should not work," Rebec said. "We now have good evidence that ceftriaxone is acting on GLT1 and that the nucleus accumbens is the critical site."

Rebec said prior work on Huntington’s disease, a neurodegenerative disorder, alerted him and his team to the way ceftriaxone acts on the expression of GLT1, a protein that removes glutamate from the brain. Glutamate removal is a problem in Huntington’s disease, and Rebec’s team found that ceftriaxone increases GLT1 and improves neurological signs of the disease in mouse models.

It now is important to determine why cocaine decreases GLT1 and to see whether other drugs of abuse have the same effect. Rebec and colleagues have shown that ceftriaxone also can decrease the craving for alcohol in rats selectively bred to prefer alcohol.

Drug cues are one factor that can trigger relapse. Future work also will examine whether ceftriaxone can block drug craving induced by stress or by re-exposure to the drug. If so, it would mean that GLT1 could become an important target in the search for treatments to prevent drug relapse. Now, Rebec said, there are a number of factors to study. “We don’t yet know how long the effects of ceftriaxone last. Does an addict have to be on it for a month or will it lose its effectiveness? We don’t yet know what will happen.”

In the cocaine study, the rats self-administer cocaine for six hours a day for up to 11 days. Their behavior is much like that of a human addict.

"You might think that because they’re in there, they just take more, but they don’t just take more," Rebec said. "Like human addicts, they take the drug more and more rapidly and they want to get to it more and more quickly."

Withdrawal serves as an incubation period during which craving increases if it is activated by cues or other factors. “Something changes in the brain during that time to trigger the craving or make it more likely that you want the drug,” Rebec said. “That’s what ceftriaxone seems to be interfering with.”

Ceftriaxone is now in clinical trials on people with ALS, also known as Lou Gehrig’s disease, which has many mechanisms in common with other neurodegenerative diseases such as Huntington’s disease and Alzheimer’s.

Brain Visualization Prototype Holds Promise for Precision Medicine

The ability to combine all of a patient’s neurological test results into one detailed, interactive “brain map” could help doctors diagnose and tailor treatment for a range of neurological disorders, from autism to epilepsy. But before this can happen, researchers need a suite of automated tools and techniques to manage and make sense of these massive complex datasets.

To get an idea of what these tools would look like, computational researchers from the Lawrence Berkeley National Laboratory (Berkeley Lab) are working with neuroscientists from the University of California, San Francisco (UCSF). So far, the Berkeley Lab team has used existing computational tools to translate UCSF laboratory data into 3D visualizations of brain structures and activity. Earlier this year, Los Angeles-based Oblong Industries joined the collaboration and implemented a state-of-the-art, gesture-based navigation interface that allows researchers to interactively explore 3D brain visualizations with hand poses movements.

Researchers from Berkeley Lab, UCSF and Oblong Industries presented a  prototype of their brain simulation and innovative navigation interface at UCSF’s OME Precision Medicine Summit on Thursday, May 2.

“The collaboration with Oblong will make our visualizations much more powerful and relevant to precision medicine,” says Daniela Ushizima, a Berkeley Lab computational researcher who is one of the collaboration’s principal investigators. “This collaboration gives us the opportunity to have tools to browse big data sets at our fingertips, literally.”

Designed to generate actionable projects and collaborations, the OME Precision Medicine Summit brought together leaders in health, bioscience, technology, government and other fields to lay out a roadmap and remove barriers for the evolving field known as precision medicine. The field of precision medicine will allow future doctors to cross-reference an individual’s personal history and biology with patterns found worldwide and use that network of knowledge to pinpoint and deliver care that’s preventive, targeted, timely and effective.
The Future: Tackling Neuroimaging’s Big Data Problem

According to Ushizima, the brain visualization prototype provides just a small glimpse of what the collaboration hopes to achieve. Ultimately, they would like to incorporate chemical elements captured by Positron Emission Tomography (PET) scans, electrical brain activity captured by Functional Magnetic Resonance Imaging (fMRI) and anatomical structure as captured by T1, T2 and other MRI scans.

As the collaboration continues, scientists in Berkeley Lab’s Visualization and Analytics Group hope to develop tools and techniques for imaging processing and analysis. This team will also develop methods for visualizing and comparing different modalities of brain data, for instance, figuring out how to compare an anatomical brain region (like the frontal cortex) with correlating chemical activity.

Meanwhile, researchers in the Berkeley Lab’s Future Technologies, Scientific Computing and Complex Systems groups will use graph analytics and image analysis algorithms to quantify and visualize this “multi-modal” data, giving researchers the flexibility to look at regions of interest by displaying electrical, anatomical and chemical activity. By representing brain data on dynamical graphs, neuroscientists will be able to see how different parts of the brain correlate with each other. They will also be able to identify and track temporal changes, or changes over time.

“The technologies that exist for imaging the brain are very advanced and diverse. We have machines that provide extremely high-throughput, high-definition images of the brain in 3D, but unfortunately the tools to analyze this information have not advanced as quickly,” says Ushizima.

She notes that a relatively small amount of data collected from these imaging machines requires some level of manual curation, a process that can take anywhere from six months to a year. By automating and parallelizing this process, Ushizima believes this collaboration could change the paradigm.