amygdala
The Amazing Brain: Tight-Knit Connections
Posted on by Lawrence Tabak, D.D.S., Ph.D.
You’ve likely seen pictures of a human brain showing its smooth, folded outer layer, known as the cerebral cortex. Maybe you’ve also seen diagrams highlighting some of the brain’s major internal, or subcortical, structures.
These familiar representations, however, overlook the brain’s intricate internal wiring that power our thoughts and actions. This wiring consists of tightly bundled neural projections, called fiber tracts, that connect different parts of the brain into an integrated neural communications network.
The actual patterns of these fiber tracts are represented here and serve as the featured attraction in this award-winning image from the 2022 Show Us Your BRAINs Photo and Video contest. The contest is supported by NIH’s Brain Research through Advancing Innovative Neurotechnologies® (BRAIN) Initiative.
Let’s take a closer look. At the center of the brain, you see some of the major subcortical structures: hippocampus (orange), amygdala (pink), putamen (magenta), caudate nucleus (purple), and nucleus accumbens (green). The fiber tracts are presented as colorful, yarn-like projections outside of those subcortical and other brain structures. The various colors, like a wiring diagram, distinguish the different fiber tracts and their specific connections.
This award-winning atlas of brain connectivity comes from Sahar Ahmad, Ye Wu, and Pew-Thian Yap, The University of North Carolina, Chapel Hill. The UNC Chapel Hill team produced this image using a non-invasive technique called diffusion MRI tractography. It’s an emerging approach with many new possibilities for neuroscience and the clinic [1]. Ahmad’s team is putting it to work to map the brain’s many neural connections and how they change across the human lifespan.
In fact, the connectivity atlas you see here isn’t from a single human brain. It’s actually a compilation of images of the brains of multiple 30-year-olds. The researchers are using this brain imaging approach to visualize changes in the brain and its fiber tracts as people grow, develop, and mature from infancy into old age.
Sahar says their comparisons of such images show that early in life, many dynamic changes occur in the brain’s fiber tracts. Once a person reaches young adulthood, the connective wiring tends to stabilize until old age, when fiber tracts begin to break down. These and other similarly precise atlases of the human brain promise to reveal fascinating insights into brain organization and the functional dynamics of its architecture, now and in the future.
Reference:
[1] Diffusion MRI fiber tractography of the brain. Jeurissen B, Descoteaux M, Mori S, Leemans A. NMR Biomed. 2019 Apr;32(4):e3785.
Links:
Brain Basics: Know Your Brain (National Institute of Neurological Disorders and Stroke/NIH)
Sahar Ahmad (The University of North Carolina, Chapel Hill)
Ye Wu (The University of North Carolina, Chapel Hill)
Pew-Thian Yap (The University of North Carolina, Chapel Hill)
Brain Research through Advancing Innovative Neurotechnologies® (BRAIN) Initiative (NIH)
Show Us Your BRAINs Photo & Video Contest (BRAIN Initiative)
NIH Support: BRAIN Initiative; National Institute of Mental Health
Precision Deep Brain Stimulation Shows Initial Promise for Severe Depression
Posted on by Dr. Francis Collins
For many people struggling with depression, antidepressants and talk therapy can help to provide relief. But for some, the treatments don’t help nearly enough. I’m happy to share some early groundbreaking research in alleviating treatment-resistant depression in a whole new way: implanting a pacemaker-like device capable of delivering therapeutic electrical impulses deep into the brain, aiming for the spot where they can reset the depression circuit.
What’s so groundbreaking about the latest approach—so far, performed in just one patient—is that the electrodes didn’t simply deliver constant electrical stimulation. The system could recognize the specific pattern of brain activity associated with the patient’s depressive symptoms and deliver electrical impulses to the brain circuit where it could provide the most relief.
While much more study is needed, this precision approach to deep brain stimulation (DBS) therapy offered immediate improvement to the patient, a 36-year-old woman who’d suffered from treatment-resistant major depressive disorder since childhood. Her improvement has lasted now for more than a year.
This precision approach to DBS has its origins in clinical research supported through NIH’s Brain Research Through Advancing Innovative Neurotechnologies® (BRAIN) Initiative. A team, led by Edward Chang, a neurosurgeon at the University of California San Francisco’s (UCSF) Epilepsy Center, discovered while performing DBS that the low mood in some patients with epilepsy before surgery was associated with stronger activity in a “subnetwork” deep within the brain’s neural circuitry. The subnetwork involved crosstalk between the brain’s amygdala, which mediates fear and other emotions, and the hippocampus, which aids in memory.
Researchers led by Andrew Krystal, UCSF, Weill Institute for Neurosciences, attempted in the latest work to translate this valuable lead into improved care for depression. Their results were published recently in the journal Nature Medicine [1].
Krystal and colleagues, including Chang and Katherine Scangos, who is the first author of the new study, began by mapping patterns of brain activity in the patient that was associated with the onset of her low moods. They then customized an FDA-approved DBS device to respond only when it recognized those specific patterns. Called NeuroPace® RNS®, the device includes a small neurostimulator and measures about 6 by 3 centimeters, allowing it to be fully implanted inside a person’s skull. There, it continuously monitors brain activity and can deliver electrical stimulation via two leads, as shown in the image above [2].
Researchers found they could detect and predict high symptom severity best in the amygdala, as previously reported. The next question was where the electrical stimulation would best relieve those troubling brain patterns and associated symptoms. They discovered that stimulation in the brain’s ventral capsule/ventral striatum, part of the brain’s circuitry for decision-making and reward-related behavior, led to the most consistent and sustained improvements. Based on these findings, the team devised an on-demand and immediate DBS therapy that was unique to the patient’s condition.
It will be important to learn whether this precision approach to DBS is broadly effective for managing treatment-resistant depression and perhaps other psychiatric conditions. It will take much more study and time before such an approach to treating depression can become more widely available. Also, it is not yet clear just how much it would cost. But these remarkable new findings certainly point the way toward a promising new approach that will hopefully one day bring another treatment option for those in need of relief from severe depression.
References:
[1] Closed-loop neuromodulation in an individual with treatment-resistant depression. Scangos KW, Khambhati AN, Daly PM, Makhoul GS, Sugrue LP, Zamanian H, Liu TX, Rao VR, Sellers KK, Dawes HE, Starr PA, Krystal AD, Chang EF. Nat Med. 2021 Oct;27(10):1696-1700
[2] The NeuroPace® RNS® System for responsive neurostimulation, NIH BRAIN Initiative.
Links:
Depression (National Institute of Mental Health/NIH)
Deep Brain Stimulation for Parkinson’s Disease and other Movement Disorders (National Institute of Neurological Disorders and Stroke/NIH)
Andrew Krystal (University of California San Francisco)
Katherine Scangos (UCSF)
Edward Chang (UCSF)
NIH Support: National Institute of Neurological Disorders and Stroke
Distinctive Brain ‘Subnetwork’ Tied to Feeling Blue
Posted on by Dr. Francis Collins
Credit: :iStock/kieferpix
Experiencing a range of emotions is a normal part of human life, but much remains to be discovered about the neuroscience of mood. In a step toward unraveling some of those biological mysteries, researchers recently identified a distinctive pattern of brain activity associated with worsening mood, particularly among people who tend to be anxious.
In the new study, researchers studied 21 people who were hospitalized as part of preparation for epilepsy surgery, and took continuous recordings of the brain’s electrical activity for seven to 10 days. During that same period, the volunteers also kept track of their moods. In 13 of the participants, low mood turned out to be associated with stronger activity in a “subnetwork” that involved crosstalk between the brain’s amygdala, which mediates fear and other emotions, and the hippocampus, which aids in memory.
Creative Minds: Seeing Memories in a New Light
Posted on by Dr. Francis Collins
Steve Ramirez/Joshua Sariñana
Whether it’s lacing up for a morning run, eating blueberry scones, or cheering on the New England Patriots, Steve Ramirez loves life and just about everything in it. As an undergraduate at Boston University, this joie de vivre actually made Ramirez anxious about choosing just one major. A serendipitous conversation helped him realize that all of the amazing man-made stuff in our world has a common source: the human brain.
So, Ramirez decided to pursue neuroscience and began exploring the nature of memory. Employing optogenetics (using light to control brain cells) in mice, he tagged specific neurons that housed fear-inducing memories, making the neurons light sensitive and amenable to being switched on at will.
In groundbreaking studies that earned him a spot in Forbes 2015 “30 Under 30” list, Ramirez showed that it’s possible to reactivate memories experimentally in a new context, recasting them in either a more negative or positive behavior-changing light [1–3]. Now, with support from a 2016 NIH Director’s Early Independence Award, Ramirez, who runs his own lab at Boston University, will explore whether activating good memories holds promise for alleviating chronic stress and psychiatric disease.
Creative Minds: Helping More Kids Beat Anxiety Disorders
Posted on by Dr. Francis Collins
Dylan Gee
While earning her Ph.D. in clinical psychology, Dylan Gee often encountered children and adolescents battling phobias, panic attacks, and other anxiety disorders. Most overcame them with the help of psychotherapy. But not all of the kids did, and Gee spent many an hour brainstorming about how to help her tougher cases, often to find that nothing worked.
What Gee noticed was that so many of the interventions she pondered were based on studies in adults. Little was actually known about the dramatic changes that a child’s developing brain undergoes and their implications for coping under stress. Gee, an assistant professor at Yale University, New Haven, CT, decided to dedicate her research career to bridging the gap between basic neuroscience and clinical interventions to treat children and adolescents with persistent anxiety and stress-related disorders.
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