Anxiety Control: A Portion of hippocampus found to play a major role

Columbia University Medical Center (CUMC) researchers have found the first evidence that selective activation of the dentate gyrus, a portion of the hippocampus, can reduce anxiety without affecting learning. 

The findings suggest that therapies that target this brain region could be used to treat certain anxiety disorders, such as panic disorder and post-traumatic stress syndrome (PTSD), with minimal cognitive side effects.

The study, conducted in mice, was published today in the online edition of the journal Neuron. The dentate gyrus is known to play a key role in learning.

Rene Hen

Some evidence suggests that the structure also contributes to anxiety. "But until now no one has been able to figure out how the hippocampus could be involved in both processes," said senior author Rene Hen, PhD, professor of neuroscience and pharmacology (in psychiatry) at CUMC.

"It turns out that different parts of the dentate gyrus have somewhat different functions, with the dorsal portion largely dedicated to learning and the ventral portion dedicated to anxiety," said lead author Mazen A. Kheirbek, PhD, a postdoctoral fellow in neuroscience at CUMC.

To examine the role of the dentate gyrus in learning and anxiety, the investigators used a state-of-the-art technique called optogenetics, in which light-sensitive proteins, or opsins, are genetically inserted into neurons in the brains of mice.

Neurons with these genes can then be selectively activated or silenced through the application of light (via a fiber-optic strand), allowing researchers to study the function of the cells in real time.

Previously, the only way to study the dentate gyrus was to silence portions of it using such long-term manipulations as drugs or lesions, techniques that yielded conflicting results.

In the current study, opsins were inserted into dentate gyrus granule cells (the principal cells of the dentate gyrus).

The researchers then activated or silenced the ventral or dorsal portions of the dentate gyrus for three minutes at a time, while the mice were subjected to two well-validated anxiety tests (the elevated plus maze and the open field test).

"Our main findings were that elevating cell activity in the dorsal dentate gyrus increased the animals' desire to explore their environment. But this also disrupted their ability to learn. Elevating activity in the ventral dentate gyrus lowered their anxiety, but had no effect on learning," said Dr. Kheirbek.

The effects were completely reversible—that is, when the stimulation was turned off, the animals returned to their previous anxiety levels.

"The therapeutic implication is that it may be possible to relieve anxiety in people with anxiety disorders by targeting the ventral dentate gyrus, perhaps with medications or deep-brain stimulation, without affecting learning," said Dr. Hen.

Dr Hen is also a director of the Division of Integrative Neuroscience, The New York State Psychiatric Institute, and a member of The Kavli Institute for Brain Science.

"Given the immediate behavioral impact of such manipulations, these strategies are likely to work faster than current treatments, such as serotonin reuptake inhibitors."

According to Dr. Hen, such an intervention would probably work best in people with panic disorder or PTSD.

"There is evidence that people with these anxiety disorders tend to have a problem with pattern separation—the ability to distinguish between similar experiences," he said.

"In other words, they overgeneralize, perceiving minor threats to be the same as major ones, leading to a heightened state of anxiety. Such patients could conceivably benefit from therapies that fine-tune hippocampal activity."

Dr. Hen and his team are currently exploring strategies aimed at modulating the activity of the ventral dentate gyrus by stimulating neurogenesis in the ventral dentate gyrus.

"Indeed the dentate gyrus is one of the few areas in the adult brain where neurons are continuously produced, a phenomenon termed adult hippocampal neurogenesis," added Dr. Hen.

More information: The title of the paper is "Differential control of learning and anxiety along the dorso-ventral axis of the dentate gyrus."  

Brain Structure of Infants predicts Language Skills at one year

Using a brain-imaging technique that examines the entire infant brain, researchers have found that the anatomy of certain brain areas – the hippocampus and cerebellum – can predict children's language abilities at 1 year of age. 

The University of Washington study is the first to associate these brain structures with future language skills. 

The results are published in the January issue of the journal Brain and Language.

"The brain of the baby holds an infinite number of secrets just waiting to be uncovered, and these discoveries will show us why infants learn languages like sponges, far surpassing our skills as adults," said co-author Patricia Kuhl, co-director of the UW's Institute for Learning & Brain Sciences.

Children's language skills soar after they reach their first birthdays, but little is known about how infants' early brain development seeds that path.

Identifying which brain areas are related to early language learning could provide a first glimpse of development going awry, allowing for treatments to begin earlier.

"Infancy may be the most important phase of postnatal brain development in humans," said Dilara Deniz Can, lead author and a UW postdoctoral researcher.

"Our results showing brain structures linked to later language ability in typically developing infants is a first step toward examining links to brain and behavior in young children with linguistic, psychological and social delays."

In the study, the researchers used magnetic resonance imaging to measure the brain structure of a mix of 19 boys and girls at 7 months of age.

The researchers used a measurement called voxel-based morphometry to determine the concentration of gray matter, consisting of nerve cells, and of white matter, which make up the network of connections throughout the brain.

The study is the first to relate the outcomes of this whole-brain imaging technique to predict future ability in infants.

The whole-brain approach freed the researchers from having to select a few brain regions for study ahead of time, ones scientists might have expected to be involved based on adult data.

Read the full article at: Medical Express

Language learning makes the brain grow, Swedish study

At the Swedish Armed Forces Interpreter Academy, young recruits learn a new language at a very fast pace.

By measuring their brains before and after the language training, a group of researchers has had an almost unique opportunity to observe what happens to the brain when we learn a new language in a short period of time.

At the Swedish Armed Forces Interpreter Academy in the city of Uppsala, young people with a flair for languages go from having no knowledge of a language such as Arabic, Russian or Dari to speaking it fluently in the space of 13 months.

From morning to evening, weekdays and weekends, the recruits study at a pace unlike on any other language course.

As a control group, the researchers used medicine and cognitive science students at Umeå University -- students who also study hard, but not languages.

Both groups were given MRI scans before and after a three-month period of intensive study. While the brain structure of the control group remained unchanged, specific parts of the brain of the language students grew.

The parts that developed in size were the hippocampus, a deep-lying brain structure that is involved in learning new material and spatial navigation, and three areas in the cerebral cortex.

"We were surprised that different parts of the brain developed to different degrees depending on how well the students performed and how much effort they had had to put in to keep up with the course," says Johanna Mårtensson, a researcher in psychology at Lund University, Sweden.

Students with greater growth in the hippocampus and areas of the cerebral cortex related to language learning (superior temporal gyrus) had better language skills than the other students.

In students who had to put more effort into their learning, greater growth was seen in an area of the motor region of the cerebral cortex (middle frontal gyrus).

The areas of the brain in which the changes take place are thus linked to how easy one finds it to learn a language and development varies according to performance.

Previous research from other groups has indicated that Alzheimer's disease has a later onset in bilingual or multilingual groups.

"Even if we cannot compare three months of intensive language study with a lifetime of being bilingual, there is a lot to suggest that learning languages is a good way to keep the brain in shape," says Johanna Mårtensson.