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November 6, 2015
Digest

Study in Mice Shows How Brain Ignores Distractions

The brain’s attentional spotlight: Scientists mapped out the brain circuitry that helps mice focus.

The brain’s attentional spotlight: Scientists mapped out the brain circuitry that helps mice focus.

IMAGE: DR. MICHAEL HALASSA, NEW YORK UNIVERSITY LANGONE MEDICAL CENTER

In a study of mice, scientists discovered that a brain region called the thalamus may be critical for filtering out distractions. The study, published in Nature and partially funded by NIH, paves the way to understanding how defects in the thalamus might underlie symptoms seen in patients with autism, attention deficit hyperactivity disorder and schizophrenia.

“We are constantly bombarded by information from our surroundings,” said Dr. James Gnadt, program director at the National Institute of Neurological Disorders and Stroke. “This study shows how the circuits of the brain might decide which sensations to pay attention to.” Thirty years ago, Dr. Francis Crick proposed that the thalamus “shines a light” on regions of the cortex, which readies them for the task at hand, leaving the rest of the brain’s circuits to idle in darkness.

“We typically use a very small percentage of incoming sensory stimuli to guide our behavior, but in many neurological disorders the brain is overloaded,” said Dr. Michael Halassa, the study’s senior author and an assistant professor at New York University’s Langone Medical Center. “It gets a lot of sensory input that is not well-controlled because this filtering function might be broken.”

Researchers Identify Potential Alternative to CRISPR-Cas Genome Editing Tools

An international team of CRISPR-Cas researchers has identified three new naturally occurring systems that show potential for genome editing. The discovery and characterization of these systems is expected to further expand the genome editing toolbox, opening new avenues for biomedical research. The research, published Oct. 22 in the journal Molecular Cell, was supported in part by NIH.

“This work shows a path to discovery of novel CRISPR-Cas systems with diverse properties, which are demonstrated here in direct experiments,” said Dr. Eugene Koonin, senior investigator at the National Center for Biotechnology Information, National Library of Medicine. “The most remarkable aspect of the story is how evolution has achieved a broad repertoire of biological activities, a feat we can take advantage of for new genome manipulation tools.”

Enzymes from the CRISPR system are revolutionizing the field of genomics, allowing researchers to target specific regions of the genome and edit DNA at precise locations. “CRISPR” stands for clustered regularly interspaced short palindromic repeats, which are key components of a system used by bacteria to defend against invading viruses. Cas9—one of the enzymes produced by the CRISPR system—binds to the DNA in a highly sequence-specific manner and cuts it, allowing precise manipulation of a region of DNA. Enzymes such as Cas9 provide researchers with a gene-editing tool that is faster, less expensive and more precise than previously developed methods.

The three newly characterized systems share some features with Cas9 and Cpf1, a recently characterized CRISPR enzyme, but have unique properties that could potentially be exploited for novel genome editing applications. This study highlights the diversity of CRISPR systems, which can be leveraged to develop more efficient, effective and precise ways to edit DNA.

Prevalence of Marijuana Use Among U.S. Adults Doubles Over Past Decade

The percentage of Americans who reported using marijuana in the past year more than doubled between 2001-2002 and 2012-2013, and the increase in marijuana use disorder during that time was nearly as large. Past year marijuana use rose from 4.1 percent to 9.5 percent of the U.S. adult population, while the prevalence of marijuana use disorder rose from 1.5 percent to 2.9 percent, according to national surveys conducted by the National Institute on Alcohol Abuse and Alcoholism.

“Based on the results of our surveys, marijuana use in the United States has risen rapidly over the past decade, with about 3 in 10 people who use marijuana meeting the criteria for addiction. Given these increases, it is important that the scientific community convey information to the public about the potential harms,” said NIAAA director Dr. George Koob.

Data about marijuana use was collected as part of NIAAA’s National Epidemiologic Survey on Alcohol and Related Conditions, a series of the largest epidemiological surveys of their kind. In total, 79,000 people were interviewed on alcohol use, drug use and related psychiatric conditions during the 2001-2002 and 2012-2013 surveys.

The analysis appeared in the Oct. 21 issue of the Journal of the American Medical Association Psychiatry and was led by Dr. Bridget Grant of NIAAA’s Laboratory of Epidemiology and Biometry.

The marked increase in marijuana use and marijuana use disorder shown in the study is a significant change from prior results. Earlier NIAAA research found that marijuana use remained stable at about 4 percent of the U.S. population between 1991-1992 and 2001-2002, while abuse and dependence rose from 1.2 percent to 1.5 percent.

Based on the current study, approximately 30 percent of people who used marijuana in the past year met criteria for marijuana use disorder during 2012-2013.

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