Brain Cell Growth And Mental Disorders

§ March 20th, 2009 § Filed under brain research, depression, neuroscience § No Comments

A new study in “Cell” connects the mechanism that produces new brain cells in adults with the incidence of schizophrenia and other neuropsychiatric disorders. The study, supports a controversial theory linking diseases such as schizophrenia and depression to neurogenesis and provides new avenues for the possible treatment of such conditions.

Image: flicker/Staurland

“This is the first time anybody has ever shown that this protein [coded by the gene] directly regulates the number of neural progenitors,” said Li-Huei Tsai, the study’s main author and a neuroscientist at the Picower Institute of Learning and Memory at the Massachusetts Institute of Technology.

Prior studies linked disturbances in neurogenesis in a brain region called the hippocampus to schizophrenia and suggested that anti-depressant medications such as Prozac work by stimulating hippocampal neurogenesis. The new findings link the gene, DISC1, to a signal pathway that controls neurogenesis and the development of the nervous system.

“It really fits in with a lot of background information to suggest that hippocampal neurogenesis in particular is potentially a process which is going wrong in psychiatric illness,” said Ben Pickard, a medical geneticist at the University of Edinburgh (not involved in the study).

Researchers first connected DISC1 and psychiatric disorders in 2001 — a large Scottish family with a high incidence of schizophrenia and bipolar disorder had a significant disruption in the gene’s sequence. Tsai and others have since linked other mutations in the gene to psychiatric disorders.

Tsai and her colleagues showed that the DISC1 protein “inhibits the inhibition” of neurogenesis. A mutation in the gene therefore can lead to the undisturbed inhibition neuronal growth. In adult mice, blocking the action of the DISC1 protein resulted in the display of symptoms associated with schizophrenia and depression.

GSK3-beta is the molecular target of lithium, the most effective treatment available for bipolar disorder. Although the compound has been used for decades, how it works is largely unknown. Tsai’s findings suggest that lithium’s mechanism may involve stimulating neurogenesis. “One of the most exciting aspects of the study is the parallel between this one function and lithium,” said Tsai.

It may also provide a genetic means of predicting which patients will respond to lithium. This is “giving us clues as to why the medications might work in some people and not in others,” said David Porteous, a molecular geneticist also at the University of Edinburgh (also not involved in the present work, but coauthor of the original DISC1 family study). “It’s not just a very good piece of science; it’s also giving us a roadmap to what we should be doing next.”

“We’re starting to develop a kind of genetic network around the DISC1 pathway,” he said, which points to “targets for intervention in a much more rational fashion than what’s been possible.”

I’d add that it might also provide an interesting avenue for non-drug therapy using brain exercises that promote neurogenesis.

Other posts related to mental health and neurogenesis:

How exercise and brain exercise can help combat depression

More on Depression And Brain Exercise

Brain Activity And First Impressions

§ March 10th, 2009 § Filed under brain research, neuroscience, plasticity § No Comments

(This is proving to be a bonanza day for new research.)

Scientists from NYU and Harvard devised a rather unwieldy sounding study that nevertheless produced compelling indications that there’s a lot going on in our heads when we meet someone for the first time. The team provided subjects with written profiles and pictures of fictitious individuals, each seeded with “trait” information that would commonly inspire some kind of judgment. They used neuroimaging to record what was happening in the subjects brains as they reached their first impressions about the characters.

The neuroimaging results showed significant activity in two regions of the brain: The amygdala, a small structure in the medial temporal lobe previously linked to emotional learning about inanimate objects and social evaluations based on trust or race group. And the posterior cingulate cortex (PCC), linked to economic decision-making and assigning subjective value to rewards.

“Even when we only briefly encounter others, brain regions that are important in forming evaluations are engaged, resulting in a quick first impression,” said NYU’s Dr. Elizabeth Phelps.

NYU’s Dr. Daniela Schiller, the study’s lead author, concluded, “When encoding everyday social information during a social encounter, these regions sort information based on its personal and subjective significance, and summarize it into an ultimate score–a first impression.”

Brain Wiring And Gender Differences

§ March 10th, 2009 § Filed under brain research § No Comments

This is a somewhat lightweight but fundamentally interesting piece on gender differences in the brain. It argues that there are gender differences, but that environmental differences are far more influential.

I’d quibble with the idea that just because 90% of connections get made as we develop, this directly implies that environment far outweighs gender differences. (I don’t necessarily disagree with the conclusion, but it doesn’t necessarily follow.) After all, if epigenetic changes can happen in the brain affecting the next generation, saying that we have only 10% of neuronal connections at birth isn’t quite as stark a statement as it seems. The remaining 90% of connections would still be made with reference to the individuals DNA as well as the existing wiring…

Brain Plasticity – Proof of Long Term Rewiring

§ March 10th, 2009 § Filed under brain research, neuroscience, plasticity § No Comments

Scientists in Tübingen, Germany have proven for the first time that widely-distributed networks of nerves in the brain can fundamentally reorganize as required…

A team from the Max Planck Institute for Biological Cybernetics in Tübingen demonstrated long term reorganization in activities of large parts of the brain. By stimulating nerve cells in the hippocampus and measuring changes with functional magnetic resonance tomography (FMRt) and electrophysiology, the team tracked reorganization in large populations of nerve cells in the forebrain (active in memory and spatial awareness). This is the first experimental proof that large parts of the brain change when we learn. (Current Biology, March 10, 2009)

Before and after images of activity in the brain following plastic change

Before and after images of activity in the brain following plastic change

Link to longer story on InSciences.

Brain Plasticity And Chronic Stress

§ February 26th, 2009 § Filed under depression, plasticity § 1 Comment

As a reminder that plastic change can be harmful as well as helpful to our mental health, scientists have identified what looks to be a process of long term damage caused by chronic stress.

“Stress and depression are known to cause a reversible retraction of dendrites in certain brain cells, particularly in the hippocampus, that McEwen and colleagues refer to as “adaptive plasticity.” The new research suggests that an increase in KA1, caused by the corticosteroid response in rats, may trigger this retraction. The finding follows recent work by Rockefeller’s Sidney Strickland, head of the Laboratory of Neurobiology and Genetics, that showed that KA1 production explodes in the hippocampus during simulated stroke in mice, driving a cell-death cascade that begins when part of the brain is deprived of blood. Combined, the work suggests that the relatively understudied KA1 subunit plays an important role in a key area of the brain in both causing damage in an uncontrolled trauma such as a stroke and in protecting the brain from damage under the more controlled circumstances of chronic stress.

“McEwen and colleagues have shown that healthy brains are remarkably resilient in the face of stress — brains replace their retracted neurons once the stress is removed. Perhaps, the researchers say, the same will prove true for depression. “One of the great hopes is that these changes in the hippocampus that happen with prolonged depression may not be signs of permanent irreversible damage but they may actually be signs of plasticity that we can treat with appropriate medications and also behavioral therapies,” McEwen says.”

Brain Training – What Use New Neurons?

§ February 23rd, 2009 § Filed under brain research, neuroscience, plasticity § No Comments

Tracey J. Shors

Tracey J. Shors

In a fascinating article in Scientific American’s Mind section Tracey J. Shors, a professor in the department of psychology and the Center for Collaborative Neuroscience at Rutgers University, explains how new brain cells typically die off unless the brain is stimulated to put them to use. Shors and fellow scientists found that demanding and challenging cognitive tasks engage the brain in such a way that it assimilates the new brain cells, strengthening problem solving ability.

“Presumably the added cells, once they mature, are used to fine-tune or boost problem-solving skills that already exist.”

Shors introduces the subject with a paragraph supporting brain training.

I like scientific findings that concur with what one would think should sensibly happen — i.e., the finding that taxing the brain will strengthen cognition seems evolutionarily right.

Sleep And Brain Plasticity

§ February 12th, 2009 § Filed under brain research, neuroscience, plasticity § No Comments

Marcos Frank, PhD, Assistant Professor of Neuroscience, at the University of Pennsylvania School of Medicine, along with postdoctoral researcher Sara Aton, PhD, and colleagues have shown that the functions associated with long-term memory formation don’t become active until we sleep.

Optical Brain Maps - Plastic Change

Optical Brain Maps - Plastic Change

In a cleverly designed series of experiments, the researchers worked with the visual systems of young animals. By covering one eye of the animals with a patch the team studied the electrophysiological and molecular changes that resulted with or without sleep (and compared these to a control group with no patch).

Once triggered to reorganize its neural networks in wakefulness (by visual deprivation, for instance), the brain engages intra- and intercellular communication pathways, releasing a series of enzymes that could reorganize the appropriate neurons.

“To our amazement, we found that these enzymes never really turned on until the animal had a chance to sleep,” Dr. Frank explained, “As soon as the animal had a chance to sleep, we saw all the machinery of memory start to engage.”

(Further, by stopping these enzymes from working in the sleeping brain the normal reorganization of the cortex didn’t happen.)

But perhaps more generally interesting is the insight that the changes in some senses weren’t memory changes — although they were certainly plastic changes. The same mechanism could play a role in all neurological plasticity processes.

Musical Training And Language Ability In Children

§ February 10th, 2009 § Filed under brain research, neuroscience, plasticity § No Comments

In this study, researchers found that a relatively brief period of musical training, just six months, was enough to improve the language aptitude of a group of eight year-olds.
Musical Training Influences Linguistic Abilities in 8-Year-Old Children: More Evidence for Brain Plasticity

Benefits of Rich Infant Environment Across Generations

§ February 3rd, 2009 § Filed under brain research, neuroscience, plasticity § No Comments

Could the environment your mother grew up in affect your likelihood of developing a learning disorder, or protect you from one? This was the intriguing question posed by Larry Feig, PhD, professor of biochemistry at Tufts University School of Medicine and member of the biochemistry and neuroscience programs at the Sackler School of Graduate Biomedical Sciences at Tufts University. He set out to investigate the impact of a mother’s early environment on her offspring. He found that if a mother had a stimulating environment with novel objects and unforced exercise when she was young, the benefits of such an environment carried over to her offspring, even if they were raised by a foster mother. (This was all done with mice.)

This ‘inheritance of acquired characters,’ first proposed by Lamarck goes against pure Mendelian genetics and points to a much more rapid generic mechanism for conferring benefits or deficits across generations. Feig concludes that the mechanism may have evolved to protect infants from circumstancial sensory deprivation.

This report appeared in the Reading Eagle covering a study to be published tomorrow in the Journal of Neuroscience.

Brain Scans of Legal Decision Making

§ January 31st, 2009 § Filed under brain research, neuroscience § No Comments

I found this fascinating item over at Deric Bownd’s MindBlog.

By scanning a person’s brain activity during the process of legal decision making, scientists have discovered that determining responsibility and punishment use different parts of the brain.

When we’re judging responsibility we use the part of our brain most closely related to rational and logical decision making. But when we’re judging the degree of appropriate punishment we use the part of our brain more closely associated with subjective judgments.

This practical application of the science of brain scanning gives us a sense of how powerful and how potentially useful it will be to be able to monitor the workings of the brain in different circumstances.

Perhaps, for instance, by tweaking sentencing guidelines as we monitor brain activity, it would be possible to shift the relative involvement of objective and subjective judgment. Just a thought.

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