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Science Updates 2005

NIMH Science Updates are summaries of recent notable research findings by NIMH-funded investigators. Updates are also available for 2003, 2004, 2006, and 2007.

Updates from 2005

Sleep Reorganizes Brain Connections to Improve Performance

Sleep helps strengthen memories and improves physical performance by producing large-scale changes in brain activity that makes a skill less dependent on conscious thought, Dr. Matthew P. Walker and colleagues at Harvard Medical School has found. Twelve healthy, college-aged participants were taught a simple finger-tapping task and then retested 12 hours later, either after a night of sleep or after 12 daytime hours without sleep. The researchers monitored the participants’ brain activity using functional magnetic resonance imaging (fMRI). Those who slept performed the task with fewer errors than those in the daytime test group, and showed greater brain activation in the motor cortex and cerebellum (which control speed and accuracy) as well as in the right frontal lobe and right temporal lobe (which help create memory sequences). This increased activation suggests that sleep reinforced the memory of the task in motor control areas of the brain, allowing participants to perform the task more quickly and accurately. In addition, those who slept showed decreased brain activity in the parietal lobes (involved in conscious monitoring of physical movement) and several emotion-regulating regions, suggesting that as memory of the task was reinforced it became easier to perform without thinking about it too much. This, in turn, may have reduced the emotional burden involved in performing the task. The researchers propose that further studies are needed to find out whether a full night of sleep prompts these changes in the brain, or whether they are triggered by a specific stage of sleep. Such findings have important implications not only for learning real-life skills (such as learning a musical instrument or playing a sport), but also for physical rehabilitation (such as after a stroke), and for studying the relationship between sleep disturbances and learning problems.

Walker MP, Stickgold R, Alsop D, Gaab N, Schlaug G. Sleep-dependent motor memory plasticity in the human brain. Neuroscience. 2005. 133(4):911-917.

Monkeys Lack Circuitry for Long-Term Memory of Sounds — Clue to Language?

When remembering sounds, monkeys falter — especially over the long term — and appear to use different circuitry than for other sensory stimuli, researchers at NIMH have discovered. Drs. Jonathan Fritz, Mortimer Mishkin, and Richard Saunders suggest that their findings may shed new light on the role of auditory memories in the development of spoken language and whether it is unique to humans. Previous studies had shown that damage to monkeys’ rhinal cortices causes severe difficulties in, or loss of, an animal’s ability to remember sights, smells, tastes, and physical touch. This loss of function suggests that the rhinal cortices, located on the hippocampus (a memory hub), are part of a memory-creating circuit. To determine if the rhinal cortices play a similar role in memories of sound, the researchers trained nine rhesus monkeys to respond to paired sounds, with varying delays between the two sound cues, and identify them as either the same or different. Their first clue: it took an unusually long time for the monkeys to learn this task and the animals failed to retain memories of the sounds long-term. Still, the researchers were surprised to find that whatever ability the monkeys had to remember sounds remained intact after the rhinal cortices were surgically removed. This indicated that the way monkeys create memories of sound differs from their other senses and from other animals and humans. How monkeys in the wild remember the meaning of alarm calls signaling predators and other vital auditory messages remains a mystery, as does the existence of long-term memory mechanisms in baboons and apes. The study raises the possibility that language is unique to humans, in part, because it requires long-term auditory memory, suggest the researchers.

Fritz J, Mishkin M, Saunders RC. In Search of an Auditory Engram. Proc Natl Acad Sci USA. 20 Jun 2005; [Epub ahead of print].

New Targeted Therapy Helps Overcome Disabling Grief

A targeted treatment developed specifically for complicated grief, a debilitating disorder with symptoms similar to both depression and post-traumatic stress disorder (PTSD), showed a better response in bereaved individuals when compared with interpersonal psychotherapy (IPT), a proven treatment for grief-related depression. The targeted grief treatment modified techniques used for depression to include PTSD therapies that addressed issues of trauma and loss-specific distress. In a randomized controlled trial of 95 individuals with complicated grief, 51 percent of those treated with the targeted therapy showed improved scores on various measures of depression, compared with 28 percent showing improvement from IPT. Complicated grief affects about 10 percent to 20 percent of people suffering the loss of a loved one, or about 1 million people a year, and differs from grief and depression in that feelings of loss and disbelief do not go away and eventually affect a person’s daily functioning. It is not currently recognized by the American Psychiatric Association (APA), a distinction that the researchers, Dr. Katherine Shear and colleagues at the University of Pittsburgh, hope to have changed in the next edition of the APA’s Diagnostic and Statistical Manual of Mental Disorders.

Shear K, Frank E, Houck PR, Reynolds, CF 3rd. Treatment of complicated grief: a randomized controlled trial. JAMA. 2005 Jun 1;293(21):2601­–2608.

Genetic Variation Yields Differences in Brain Anatomy and Emotion Regulation

In a brain scan study of 114 healthy subjects, NIMH researchers found a genetic trait that may increase a person’s likelihood of developing depression and anxiety disorders. The gene region called 5-HTTLPR influences the body’s ability to make a transporter protein for serotonin, a brain chemical involved in depression and anxiety disorders and the target of most current medication therapies. People who had at least one copy of a short version of 5-HTTLPR, compared to people with two copies of the long version, showed less gray matter (brain cells and their connections) in the amygdala and cingulate, brain areas that help process and regulate emotion. The short version of 5-HTTLPR was also associated with increased anxiety-related temperamental traits, increased risk for depression, and shortfalls in the brain’s ability to reduce negative reactions and behaviors following fearful stimuli, like seeing a scary face. According to Dr. Andreas Meyer-Lindenberg, a lead author with Dr. Lukas Pezawas, “this study suggests that the cingulate’s ability to put the brakes on a runaway fear response depends upon the degree of connectivity in this circuit, which is influenced by the serotonin transporter gene.”

See full press release.

Pezawas L, Meyer-Lindenberg A, Drabant EM, Verchinski BA, Munoz KE, Kolachana BS, Egan MF, Mattay VS, Hariri AR, Weinberger DR. 5-HTTLPR polymorphism impacts human cingulated-amygdala interactions: a genetic susceptibility mechanism for depression. Nat Neurosci. 2005 Jun;8(6):828-34.

Gene May Interact with Teenage Marijuana Use to Increase Psychosis Risk

Starting to use marijuana as a teenager and having a particular gene associated with higher risk for schizophrenia may put some people at increased risk for developing psychotic disorders. The gene for the catecho-O-methyltransferase (COMT) enzyme, which breaks down the brain chemical dopamine, comes in two versions, met and val, the latter being associated with slightly higher risk for schizophrenia. People inherit two copies (one from each parent) of the COMT gene, so a person can have two of the same version or one of each. Drs. Terrie Moffitt, Avshalom Caspi, and colleagues at the University of Wisconsin have been following more than 800 New Zealanders from birth into adulthood to identify risk factors for mental disorders. In this sample, val, by itself, did not increase risk for schizophrenia or related psychotic disorders, nor did adult onset marijuana use. Yet, a significant relationship emerged when a person carried two copies of val and began smoking marijuana as a teen – a factor that also independently increased risk for psychosis in this population. Carrying two copies of the met version posed no increased risk for psychosis. The results suggest that for some people, adolescence may be a “sensitive period of neurobiological vulnerability to cannabis,” but marijuana use, even in combination with val, does not constitute a major cause of schizophrenia. People with two copies of val who used the drug as teens accounted for only one-fifth of those who developed psychotic disorders, which likely stem from multiple causes. However, the researchers point out that unless such potential gene-environment interactions are factored into studies, a gene’s connection to a disorder may remain undetected.

Caspi A, Moffitt TE, Cannon M, McClay J, Murray R, Harrington H, Taylor A, Arseneault L, Williams B, Braithwaite A, Poulton R, Craig IW. Moderation of the effect of adolescent-onset cannabis use on adult psychosis by a functional polymorphism in the catechol-o-methyltransferase gene: longitudinal evidence of a gene X environment interaction. Biol Psychiatry. 2005 May 15;57(10):1117-27.

Brain Scans Show How Gene May Boost Schizophrenia Risk

Different versions of a gene involved in regulating the brain chemical dopamine have different effects on dopamine levels in parts of the brain associated with schizophrenia. Every person inherits two copies (one from each parent) of the gene for the enzyme catecho-O-methyltransferase (COMT), which breaks down dopamine. COMT comes in two versions, val and met, so a person can have two of the same version or one of each. Earlier studies have shown that inheriting two copies of the more common val version leads to a slightly higher risk for schizophrenia and a signature pattern of dopamine activity in the midbrain. To see how the two gene versions affect living human brains, Drs. Andreas Meyer-Lindenberg, Karen Berman, and colleagues at NIMH and the National Human Genome Research Institute scanned 24 healthy young adults using positron emission tomography (PET), which allows researchers to observe brain function in living subjects. Dopamine activity in the prefrontal cortex of the brain increased as midbrain dopamine activity increased in subjects with val, but decreased in those who had inherited two copies of the met COMT gene. The findings suggest that dopamine “tunes” prefrontal neurons (brain cells) to achieve best possible functioning, much like a radio dial. For the clearest signal, the “dial” must be turned in opposite directions depending on which version of the COMT gene is inherited: up with val, down with met. In people with val and schizophrenia, which is marked by too little prefrontal and too much midbrain dopamine, the dial is turned “way up,” the NIMH researchers claim. “We expected that there would be different regulatory mechanisms between the two gene types, but it’s amazing how well the data support this tuning model,” said Berman. “The study is important for our understanding of schizophrenia because it clarifies the neural mechanism for a well-established risk gene.”

See full press release.

Meyer-Lindenberg A, Kohn PD, Kolachana B, Kippenhan S, McInerney-Leo A, Nussbaum R, Weinberger DR, Berman KF. Midbrain dopamine and prefrontal function in humans: interaction and modulation by COMT genotype. Nat Neurosci. 2005 May;8(5):594-596.

Patient Requests for Depression Medications Boost Prescribing by Physicians

People who see a doctor in response to symptoms of depression or adjustment disorder may improve their treatment by requesting an antidepressant. Direct-to-consumer (DTC) advertising of prescription drugs in the United States is both common and controversial. Critics claim that it leads to overprescribing, while supporters counter that it reduces underuse of effective treatments, especially for conditions that are poorly recognized or stigmatized. A recent randomized trial used actors portraying patients with either depression or an adjustment disorder (an excessive, atypical response to a stressful life event–such as starting school or getting divorced–or grief, such as over car accidents or natural disasters). The actor-patients were randomly assigned to make one of three types of requests: for a specific brand of antidepressant, for a non-specific (general) antidepressant, or for no medication (did not mention medication during visit). Dr. Steven Maier and colleagues at the University of Colorado found that DTC-related requests, whether for a specific antidepressant brand or not, increased the likelihood that: a doctor prescribed a medication, the patient received “minimally acceptable initial care” (defined as any combination of antidepressant, mental health referral, or follow-up visit within two weeks), and the doctor considered and recorded a mental health diagnosis.

See full press release.

Kravitz RL, Epstein MD, Franz CE, Azari R, Wilkes MS, Hinton L, Franks P. Influence of patients’ requests for direct-to-consumer advertised antidepressants: a randomized controlled trial. JAMA. 2005 Apr 27;293(16):1995-2002.

Antibiotic May Be Effective in Treating HIV-Related Disease

An antibiotic called minocycline with strong anti-inflammatory and brain cell-protective properties appears able to protect against encephalitis (brain inflammation) and loss of brain cells in monkeys infected with simian immunodeficiency virus (SIV), the equivalent to HIV in humans. Despite the availability of antiretroviral therapy, few interventions are available to treat HIV central nervous system disease, which is brought on when the virus enters and attacks the brain and frequent causes serious illness and death in HIV-positive individuals. To help fill this gap, Dr. M. Christine Zink and colleagues at Johns Hopkins University examined twelve monkeys infected with SIV and then treated with minocycline for 21 days after infection. Minocycline significantly decreased moderate and severe encephalitis in SIV treated animals and protected against nerve damage. These findings suggest that minocycline may be a readily available, cost efficient therapeutic agent to add to the anti-HIV armory.

Zink MC, Uhrlaub J, DeWitt J, Voelker T, Bullock B, Mankowski J, Tarwater P, Clements J, Barber S. Neuroprotective and anti-human immunodeficiency virus activity of minocycline. JAMA. 2005 Apr 27;293(16):2003-11.

Blood-Brain Barrier Integrity Plays Key Role in Regulating HIV Entry

Two studies have found that the HIV protein, Tat, affects two blood-brain barrier proteins, ZO-1 and claudin-5, in a way that may decrease blood-brain barrier integrity and increase entry of HIV-1 infected cells into the central nervous system. The blood-brain barrier is made up of a network of blood vessels and special brain cells (glia) that prevents some substances in the blood from entering and damaging the brain. The blood-brain barrier is also an important area of AIDS research as the spread of HIV into the central nervous system through this barrier is often seen in advanced AIDS cases and can lead to serious impairments in thinking, memory, motor functions, and behavior. These studies by Dr. Michal Toborek and colleagues at the University of Kentucky add critical knowledge not only to understanding the pathways of HIV entry into the brain but also the regulatory pathways that are central to maintaining blood-brain barrier integrity. Such knowledge could inform studies in related mental diseases such as Alzheimer’s disease, where the blood-brain barrier plays a key role in disease development.

Pu H, Tian J, Andras IE, Hayashi K, Flora G, Hennig B, Toborek M. HIV-1 Tat protein-induced alterations of ZO-1 expression are mediated by redox-regulated ERK1/2 activation. J Cereb Blood Flow Metab, 2005 Apr 13; [Epub ahead of print].

Andras IE, Pu H, Tian J, Deli MA, Nath A, Hennig B, Toborek M. Signaling mechanisms of HIV-1 Tat-induced alterations of claudin-5 expression in brain endothelial cells. J Cereb Blood Flow Metab. 2005 Mar 30; [Epub ahead of print].

What Memories are Made of Explains Their Fragility

When just a fraction of the neurons within the fear-mediating region of a rat’s brain are deprived of a key process, the rat’s memory of a fearful stimulus gets compromised, report Dr. Roberto Malinow and colleagues at Cold Spring Harbor Laboratory. Their findings underscore the critical role played by the process, the movement of a type of glutamate receptor protein into a synapse, in forming such memories – and the fragility and lack of redundancy in the workings of the system. The researchers genetically engineered ways to spy on and interfere with the activity of such AMPA receptors in the lateral amygdala. They molecularly tagged cells there to reveal when the receptors moved into synapses. Another such injection blocked the movement. The tag revealed that the receptors moved into synapses in rats conditioned to fear a tone by pairing it with a shock, but not in rats exposed to unpaired tones and shocks. Only the rats in the paired group froze when they heard the tone hours later, indicating that they had established the memory. This suggested that receptor movement was central to learning the fear response. To clinch it, the researchers then used the blocking injection to show that with impaired receptor movement, learning was dramatically reduced. By giving animals only sparse injections, they determined that disabling receptor movement in as few as 20 percent of lateral amygdala neurons is enough to disrupt learning.

Rumpel S, LeDoux J, Zador A, Malinow R. Postsynaptic receptor trafficking underlying a form of associative learning. Science. 2005 Apr 1;308(5718):83-8.

Social Cues Produce Heightened Emotional Response in Autism

In people with autism, greater than normal activity in emotion-regulating areas of the brain when looking at faces appears to contribute to characteristic behaviors of the disease. Studies have suggested that abnormal perception of faces and their social/communicative cues may contribute to the social difficulties that characterize autism. Related studies on brain function have also shown that the fusiform gyrus, a brain structure that is highly involved in typically developing individuals when looking at faces, is less involved during the same activity in individuals with autism. Following this research path, Dr. Kim Dalton and colleagues at the University of Wisconsin observed healthy participants and individuals with autism as they carried out tasks that required telling different faces apart while in an MRI scanner. In people with autism there was over-activation in the amygdala, a brain structure involved in emotional response and regulation. This activation was not specific to the emotional expression of faces, but was a response to faces in general. Activation in the fusiform gyrus and the amygdala were both strongly associated with the time the individual spent studying the eye region of the face. Over-activation in the amygdala suggests heightened emotional reaction to looking at and processing faces; greater time studying eyes was associated with greater activation in the amygdala, indicating a stronger emotional response. The authors propose a model in which face processing difficulties in autism arise from over-activation in the central circuitry of emotion, which produces heightened sensitivity to social cues.

Dalton KM, Brendon MN, Johnstone T, Schaefer HS, Gernsbacher MA, Goldsmith HH, Alexander AL, Davidson RJ. Gaze fixation and the neural circuitry of face processing in autism. Nat Neurosci. 2005 April;8(4):519-26.

Genetic Trait Linked to AIDS Resistance

The likelihood of acquiring HIV and, once infected, of progressing to full-blown AIDS, is much greater in people who have a below-average number of copies of the gene that encodes for an immune system signaling chemical (chemokine) called CCL3L1, reports a team of researchers in the US, Great Britain, and Argentina. Led by Dr. Sunil Ahuja at the University of Texas Health Science Center, the researchers selected CCL3L1 for study because it interacts with a receptor (CCR5) that is the main entry point of HIV into cells and has strong anti-HIV properties. Individuals who have both low numbers of the CCL3L1 gene and disease-accelerating CCR5 variants demonstrated a more than three-fold greater risk of rapid progression to HIV-associated dementia (general loss of intellectual abilities) and infections such as cytomegalovirus (CMV), which are associated with mental health disorders. These studies highlight a possible means to predict the susceptibility of individuals for disorders such as HIV-associated dementia, based on their genetic profiles.

Gonzalez E, Kulkarni H, Bolivar H, Mangano A, Sanchez R, Catano G, Nibbs RJ, Freedman BI, Quinones MP, Bamshad MJ, Murthy KK, Rovin BH, Bradley W, Clark RA, Anderson SA, O'Connell RJ, Agan BK, Ahuja SS, Bologna R, Sen L, Dolan MJ, Ahuja SK. The influence of CCL 3L1 gene-containing segmental duplications on HIV-1/AIDS susceptibility. Science. 2005 Mar 4;307(5714):1434-40.

Surgical Therapy Reverses Symptoms of Treatment-Resistant Depression

Deep brain stimulation, a surgical therapy that can dramatically improve symptoms in patients with Parkinson’s disease may also help people with treatment-resistant depression. Major depression is the most common psychiatric disorder, and up to 20 percent of patients do not respond to typical depression treatments. To address the needs of this severely disabled population, Dr. Helen Mayberg and colleagues at Emory University studied six individuals with treatment-resistant depression. The researchers specifically targeted the subgenual cingulated region, a brain area that in previous studies has consistently been involved in acute sadness and in responses to antidepressant treatments (such as medications or electroconvulsive therapy). Through frequent stimulation of this region, four of the six participants showed significant and sustained reduction of depression symptoms. Though additional research is needed to further study this treatment, the researchers are encouraged by the potential for deep brain stimulation to be an effective and new therapy option for severely disabled patients suffering from treatment-resistant depression.

Mayberg HS, Lozano AM, Voon V, McNeely HE, Seminowicz D, Hamani C, Schwalb JM, Kennedy SH. Deep brain stimulation for treatment-resistant depression. Neuron. 2005 Mar 3;45(5):651-660.

Motivational Prevention Counseling Reduces HIV Transmission Risk Behaviors

A relatively brief, risk-reduction counseling session may reduce the occurrence of sexual behaviors that put people at risk of becoming infected with or transmitting HIV. Dr. Seth Kalichman and colleagues at the University of Connecticut tested an HIV prevention strategy based on the information-motivation-behavioral (IMB) model that was delivered to men and women receiving clinic services for sexually transmitted infections (STI). The IMB model is a skills-building method for changing health behaviors based on three basic components: information/education, motivational enhancement, and behavioral self-management. Participants were randomly assigned to one of four 90-minute risk-reduction counseling sessions that included one, two, or all three components of the IMB model. Men who received the full IMB session showed relatively greater use of risk-reduction behavioral skills and relatively lower rates of unprotected intercourse over six months’ follow-up and had fewer new STIs. For women, however, the motivational counseling component demonstrated the most positive outcomes. This component reviewed and called attention to specific sexual behaviors that put an individual at risk for HIV infection, in order to encourage and guide changes in risky habits.

Kalichman SC, Cain D, Weinhardt L, Benotsch E, Presser K, Zweben A, Bjodstrup B, Swain GR. Experimental components analysis of brief theory-based HIV/AIDS risk-reduction counseling for sexually transmitted infection patients. Health Psychol. 2005 Mar;24(2):198-208.

Brain's Executive Hub Quells Alarm Center If Stressed

In a recent study by Dr. Steven Maier and colleagues at the University of Colorado, the medial prefrontal cortex (mPFC), an area involved in higher order functions such as problem-solving and learning from experience, was found to play an important role in managing the stress response in rats. Chemically inactivating this area and then exposing the rats to a stressful condition led to the same brainstem activity and, eventually, the same behaviors typically associated with depression and anxiety. These responses were similar to rats with functioning mPFCs exposed to stressful situations that they could not control. The researchers also found that when the mPFC deems a particular stressor controllable, it suppresses an alarm center deep in the brainstem, preventing the negative behavioral and psychological effects of uncontrollable stress. Such results imply that mood and anxiety disorders may be more about the ability to identify controllable stressors and prevent the fear response, rather than a matter of the brain responding to learned uncontrollable stressors by setting off an emotional chain reaction.

See full press release.

Amat J, Baratta MV, Paul E, Bland ST, Watkins LR, Maier SF. Medial prefrontal cortex determines how stressor controllability affects behavior and dorsal raphe nucleus. Nat Neurosci. 2005 Mar;8(3);365-71.

Prefrontal Brain Deficits May Predict Development of Schizophrenia

When performing increasingly difficult tasks, people experiencing their first episode of schizophrenia who had never taken medications for the disorder showed distinct functional shortfalls, which could potentially help identify people with schizophrenia at an earlier stage of the disease. These shortfalls were not seen in people experiencing their first episode of a mood disorder. The study, led by Dr. Angus MacDonald at the University of Minnesota, applied cognitive tests and brain imaging techniques to observe prefrontal brain functions. The specific task used in this study was able to accurately identify people with schizophrenia, as opposed to other disorders, by revealing functional problems associated with the dorsolateral prefrontal cortex of the brain. Because of these promising results, the investigators are now applying similar cognitive tests and brain imaging methods to people who meet criteria for the earliest non-psychotic stages of schizophrenia, with the goal of combining clinical, cognitive, brain imaging, and genetic analyses to enhance risk prediction in people who are at risk for serious mental illness.

MacDonald AW 3rd, Carter CS, Kerns JG, Ursu S, Barch DM, Holmes AJ, Stenger VA, Cohen JD. Specificity of prefrontal dysfunction and context processing deficits to schizophrenia in never-medicated patients with first-episode psychosis. Am J Psychiatry. 2005 Mar;162(3):475-84.

HIV Screening is Cost-Effective

In all but those at lowest-risk of becoming infected with HIV, routine, voluntary HIV screening once every 3 to 5 years may be both clinically and fiscally justified. Although US guidelines recommend routine HIV counseling, testing, and referral (HIVCTR) in healthcare centers with one percent or more HIV prevalence, roughly 280,000 Americans remain unaware that they are infected. Some scientists are concerned that current guidelines, originally created by the Center for Disease Control and Prevention (CDC) for high-risk populations (pregnant women, STD clinic workers and clients), may not be strict enough to provide the most cost-effective screening. Investigators led by Dr. David Paltiel at Yale School of Medicine developed a computer simulation to compare routine, voluntary HIVCTR to current practice (background testing and detection upon presenting with an opportunistic infection). They evaluated these practices in three target populations: “high-risk,” “CDC threshold,” and “US population.” In the “high-risk” population, adding one-time screening to current practice was associated with earlier diagnosis of HIV and increased average survival time among HIV-infected patients. In all study populations, testing every three to five years increased the cost-effectiveness per quality-adjusted life year (QALY).

Paltiel AD, Weinstein MC, Kimmel AD, Seage GR, Losina E, Zhang H, Freedberg KA, and Walensky RP. Expanded HIV screening in the United States — a cost-effectiveness analysis. N Engl J Med. 2005 Feb 10;352(6):586-95.

Adult Rat Cortex Gives Birth to New Cells

Newly generated neurons (brain cells) have been discovered in the adult rat cortex, seat of higher order “executive” functions, and in the striatum, which is involved in tasks such as forming habits and learning motor skills. The findings, by NIMH's Drs. Heather Cameron, Alexandre Dayer, and colleagues, adds to the scientific debate over the extent of the adult brain’s ability to produce new neurons, which evidence suggests may be implicated in a variety of brain disorders, including depression, Alzheimer's disease and schizophrenia. The adult cortex and striatum gave birth to new, widely scattered, small cells, called interneurons, which make and secrete the chemical messenger GABA (gamma-aminobutyric acid), which dampens brain activity. The new interneurons closely resembled those seen in other parts of the brain and seemed to arise at similar rates. Interneurons are thought to play a role in regulating larger types of neurons that make long-distance connections between brain regions.

See full press release.

Dayer AG, Cleaver KM, Abouantoun T, Cameron HA. New GABAergic interneurons in the adult neocortex and striatum are generated from different precursors. J Cell Biol. 2005 Jan 31;168(3):415-427.

High Risk of Major Depression Linked Across Three Generations

A study of the occurrence of psychiatric disorders across three generations in a family revealed that the risk of MDD, anxiety disorders, and other psychiatric disorders were highest in children with parents and grandparents who had moderately to severely impairing depression. For all three generations studied, anxiety disorders in childhood seemed to be an early indicator that a person would develop depression later in life. Such results suggest that early diagnosis and treatment is recommended for children with two generations affected by moderately to severely impairing MDD. The study was conducted by Drs. Myrna Weissman, Gerard Bruder, and colleagues at Columbia University.

Weissman MM, Wickramaratne P, Nomura Y, Warner V, Verdeli H, Pilowsky DJ, Grillon C, Bruder G. Families at high and low risk for depression: a 3-generation study. Arch Gen Psychiatry. 2005 Jan;62(1):29-36.

Science Updates are prepared by press officers in the NIMH Public Information and Communications Branch.