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A Real-Time Look at Value-Based Decision Making

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All of us make many decisions every day. For most things, such as which jacket to wear or where to grab a cup of coffee, there’s usually no right answer, so we often decide using values rooted in our past experiences. Now, neuroscientists have identified the part of the mammalian brain that stores information essential to such value-based decision making.

Researchers zeroed in on this particular brain region, known as the retrosplenial cortex (RSC), by analyzing movies—including the clip shown about 32 seconds into this video—that captured in real time what goes on in the brains of mice as they make decisions. Each white circle is a neuron, and the flickers of light reflect their activity: the brighter the light, the more active the neuron at that point in time.

All told, the NIH-funded team, led by Ryoma Hattori and Takaki Komiyama, University of California at San Diego, La Jolla, made recordings of more than 45,000 neurons across six regions of the mouse brain [1]. Neural activity isn’t usually visible. But, in this case, researchers used mice that had been genetically engineered so that their neurons, when activated, expressed a protein that glowed.

Their system was also set up to encourage the mice to make value-based decisions, including choosing between two drinking tubes, each with a different probability of delivering water. During this decision-making process, the RSC proved to be the region of the brain where neurons persistently lit up, reflecting how the mouse evaluated one option over the other.

The new discovery, described in the journal Cell, comes as something of a surprise to neuroscientists because the RSC hadn’t previously been implicated in value-based decisions. To gather additional evidence, the researchers turned to optogenetics, a technique that enabled them to use light to inactivate neurons in the RSC’s of living animals. These studies confirmed that, with the RSC turned off, the mice couldn’t retrieve value information based on past experience.

The researchers note that the RSC is heavily interconnected with other key brain regions, including those involved in learning, memory, and controlling movement. This indicates that the RSC may be well situated to serve as a hub for storing value information, allowing it to be accessed and acted upon when it is needed.

The findings are yet another amazing example of how advances coming out of the NIH-led Brain Research through Advancing Innovative Neurotechnologies® (BRAIN) Initiative are revolutionizing our understanding of the brain. In the future, the team hopes to learn more about how the RSC stores this information and sends it to other parts of the brain. They note that it will also be important to explore how activity in this brain area may be altered in schizophrenia, dementia, substance abuse, and other conditions that may affect decision-making abilities. It will also be interesting to see how this develops during childhood and adolescence.

Reference:

[1] Area-Specificity and Plasticity of History-Dependent Value Coding During Learning. Hattori R, Danskin B, Babic Z, Mlynaryk N, Komiyama T. Cell. 2019 Jun 13;177(7):1858-1872.e15.

Links:

Brain Research through Advancing Innovative Neurotechnologies® (BRAIN) Initiative (NIH)

Komiyama Lab (UCSD, La Jolla)

NIH Support: National Institute of Neurological Disorders and Stroke; National Eye Institute; National Institute on Deafness and Other Communication Disorders


How Sleep Resets the Brain

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dendrites

Caption: Colorized 3D reconstruction of dendrites. Neurons receive input from other neurons through synapses, most of which are located along the dendrites on tiny projections called spines.
Credit: The Center for Sleep and Consciousness, University of Wisconsin-Madison School of Medicine

People spend about a third of their lives asleep. When we get too little shut-eye, it takes a toll on attention, learning and memory, not to mention our physical health. Virtually all animals with complex brains seem to have this same need for sleep. But exactly what is it about sleep that’s so essential?

Two NIH-funded studies in mice now offer a possible answer. The two research teams used entirely different approaches to reach the same conclusion: the brain’s neural connections grow stronger during waking hours, but scale back during snooze time. This sleep-related phenomenon apparently keeps neural circuits from overloading, ensuring that mice (and, quite likely humans) awaken with brains that are refreshed and ready to tackle new challenges.


Creative Minds: The Worm Tissue-ome Teaches Developmental Biology for Us All

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C. elegans

Caption: An adult Caenorhabditis elegans, 5 days
Credit: Coleen Murphy, Princeton University, Princeton, NJ

In the nearly 40 years since Nobel Prize-winning scientist Sydney Brenner proposed using a tiny, transparent soil worm called Caenorhabditis elegans as a model organism for biomedical research, C. elegans has become one of the most-studied organisms on the planet. Researchers have determined that C. elegans has exactly 959 cells, 302 of which are neurons. They have sequenced and annotated its genome, developed an impressive array of tools to study its DNA, and characterized the development of many of its tissues.

But what researchers still don’t know is exactly how all of these parts work together to coordinate this little worm’s response to changes in nutrition, environment, health status, and even the aging process. To learn more, 2015 NIH Director’s Pioneer Award winner Coleen Murphy of Princeton University, Princeton, NJ, has set out to analyze which genes are active, or transcribed, in each of the major tissues of adult C. elegans, building the framework for what’s been dubbed the C. elegans “tissue-ome.”


LabTV: Curious About a Mother’s Bond

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Bianca JonesThe bond between a mother and her child is obviously very special. That’s true not only in humans, but in mice and other animals that feed and care for their young. But what exactly goes on in the brain of a mother when she hears her baby crying? That’s one of the fascinating questions being explored by Bianca Jones Marlin, the young neuroscience researcher featured in this LabTV video.

Currently a postdoctoral fellow at New York University School of Medicine, Marlin is particularly interested in the influence of a hormone called oxytocin, popularly referred to as the “love hormone,” on maternal behaviors. While working on her Ph.D.in the lab of Robert Froemke, Marlin tested the behavior and underlying brain responses of female mice—both mothers and non-mothers—upon hearing distress cries of young mice, which are called pups. She also examined how those interactions changed with the addition of oxytocin.

I’m pleased to report that the results of the NIH-funded work Marlin describes in her video appeared recently in the highly competitive journal Nature [1]. And what she found might strike a chord with all the mothers out there. Her studies show that oxytocin makes key portions of the mouse brain more sensitive to the cries of the pups, almost as if someone turned up the volume.

In fact, when Marlin and her colleagues delivered oxytocin to the brains (specifically, the left auditory cortexes) of mice with no pups of their own, they responded like mothers themselves! Those childless mice quickly learned to perk up and fetch pups in distress, returning them to the safety of their nests.

Marlin says her interest in neuroscience arose from her experiences growing up in a foster family. She witnessed some of her foster brothers and sisters struggling with school and learning. As an undergraduate at Saint John’s University in Queens, NY, she earned a dual bachelor’s degree in Biology and Adolescent Education before getting her license to teach 6th through 12th grade Biology. But Marlin soon decided she could have a greater impact by studying how the brain works and gaining a better understanding of the biological mechanisms involved in learning, whether in the classroom or through life experiences, such as motherhood.

Marlin welcomes the opportunity that the lab gives her to “be an explorer”—to ask deep, even ethereal, questions and devise experiments aimed at answering them. “That’s the beauty of science and research,” she says. “To be able to do that the rest of my life? I’d be very happy.”

References:

[1] Oxytocin enables maternal behaviour by balancing cortical inhibition. Marlin BJ, Mitre M, D’amour JA, Chao MV, Froemke RC. Nature. 2015 Apr 23;520(7548):499-504.

Links:

LabTV

Froemke Lab (NYU Langone)

Science Careers (National Institute of General Medical Sciences/NIH)

Careers Blog (Office of Intramural Training/NIH)

Scientific Careers at NIH

 


Neuroscience: The Power of Curiosity to Inspire Learning

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Snowflakes activating the brainWhen our curiosity is piqued, learning can be a snap and recalling the new information comes effortlessly. But when it comes to things we don’t care about—the recipe to that “delicious” holiday fruitcake or, if we’re not really into football, the results of this year’s San Diego County Credit Union Poinsettia Bowl—the new information rarely sticks.

To probe why this might be so, neuroscientists Charan Ranganath and Matthias Gruber, and psychologist Bernard Gelman, all at the University of California at Davis, devised a multi-step experiment to explore which regions of the brain are activated when we are curious, and how curiosity enhances our ability to learn and remember.


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