Breaking News
January 23, 2019 - Unique data combination helps FinnGen researchers to fund links between genetic factors and health
January 23, 2019 - Parents’ mental health problems associated with reactive attachment disorder in children
January 23, 2019 - Graphene Flagship project studies impact of graphene and related materials on our health
January 23, 2019 - The connection between the Pope and contraceptive pills
January 23, 2019 - Prior dengue infection could protect children from symptomatic Zika
January 23, 2019 - VISTA checkpoint implicated in pancreatic cancer immunotherapy resistance
January 23, 2019 - The Tiny Camera That Could Revolutionize Cardiovascular Surgery
January 23, 2019 - Peptide isolated from soil fungi has antitumor and antibacterial properties
January 23, 2019 - TGen identifies polio-like virus as potential cause of Acute Flaccid Myelitis outbreak
January 23, 2019 - Migrants and refugees do not bring disease and are at greater health risk themselves says WHO
January 23, 2019 - Examing the effects of menopause in workplace
January 23, 2019 - Enemy number 1 – Air pollution and climate change top of WHO agenda
January 23, 2019 - Two Positive Phase III studies of Tafenoquine for the Radical Cure of Plasmodium vivax Malaria Published in The New England Journal of Medicine
January 23, 2019 - World Trade Center responders at increased risk for head and neck cancers
January 23, 2019 - Low-sugar diet leads to significant improvement in nonalcoholic fatty liver disease in boys
January 23, 2019 - Chaos in bodily regulation can optimize our immune system, finds study
January 23, 2019 - Short, text-based exercises can increase happiness for adults recovering from substance use disorders
January 23, 2019 - Body size may have greater influence on women’s lifespan than men
January 23, 2019 - Groundbreaking tool helps visualize neuronal activity with near-infrared light
January 23, 2019 - Holocaust survivors with PTSD and their offspring exhibit more unhealthy behavior patterns
January 23, 2019 - Scientists discover new genetic mutations causing inherited deaf-blindness
January 23, 2019 - UC team designs new naloxone-dispensing smart device
January 23, 2019 - Torrent Pharmaceuticals Limited Issues Voluntary Nationwide Recall of Losartan Potassium Tablets, USP and Losartan Potassium and Hydrochlorothiazide Tablets, USP
January 23, 2019 - Brain activity shows development of visual sensitivity in autism
January 23, 2019 - Two hour gap between dinner and sleep is overrated says Japanese research
January 23, 2019 - Fear and embarrassment are causing smear test numbers to plummet
January 23, 2019 - Protein-secreting device implanted in epileptic rats reduces seizures, improves cognition
January 23, 2019 - Reintroduction project recovers current wild population of green turtle in Cayman Islands
January 23, 2019 - Cancer survivors face greater financial burden related to medical bills
January 23, 2019 - PSA screening reduces prostate cancer deaths by 30%
January 23, 2019 - LSTM receives grant to help improve health of people living in informal settlements
January 23, 2019 - Hemochromatosis Mutation Linked to Other Morbidity
January 23, 2019 - Why early diagnosis of autism should lead to early intervention
January 23, 2019 - Aspirin May Lower Stroke Risk in Women with History of Preeclampsia
January 23, 2019 - Exposure to certain chemicals may be linked to decrease in blood pressure during pregnancy
January 23, 2019 - Bowel cancer on the rise among younger Australians
January 23, 2019 - Scientists have reversed memory loss in a mouse model of Alzheimer’s
January 23, 2019 - Defective molecular master switch could lead to age-related macular degeneration
January 23, 2019 - Researchers identify how concussions may contribute to seizures
January 23, 2019 - Short interval between last meal of the day and bedtime may not affect blood glucose levels
January 23, 2019 - Still Too Many Highway Deaths Tied to Speeding
January 23, 2019 - Prenatal valproate exposure linked to increased ADHD risk
January 23, 2019 - Compound identified that may help treat heart failure
January 23, 2019 - Undiagnosed Asthma in Urban Adolescents May Be Common
January 23, 2019 - Study describes metabolism of intestinal microbiota in babies for the first time
January 22, 2019 - Study links concussions to development of epilepsy
January 22, 2019 - Specialist-led hospital bereavement service may help restrain legal action after difficult deaths
January 22, 2019 - Genetic study reveals possible new routes to treating osteoarthritis
January 22, 2019 - Blood test may detect early signs of lung-transplant rejection
January 22, 2019 - Blood marker could aid in early prediction of Alzheimer’s progression
January 22, 2019 - Orthodontic treatment does not guarantee future dental health
January 22, 2019 - Rutgers researchers discover cause of bone loss in people with joint replacements
January 22, 2019 - Diversity among rural Africans extends to their gut microbiomes
January 22, 2019 - Newly developed biological system lets cells to create self-curving cornea
January 22, 2019 - VTv Therapeutics Announces Publication of Comprehensive Data in Science Translational Medicine Detailing the Discovery and Clinical Development of TTP399, including Results of Phase 2 AGATA Study
January 22, 2019 - about one in three adults with prediabetes has arthritis
January 22, 2019 - A look at how data is democratizing health care
January 22, 2019 - Alcohol-Linked Disease Overtakes Hep C As Top Reason For Liver Transplant
January 22, 2019 - Researchers identify new genes linked with age-related macular degeneration
January 22, 2019 - MPFI researchers identify synaptic logic for connections between two brain hemispheres
January 22, 2019 - New approach to reduce toxic protein production in ALS
January 22, 2019 - New study extends our knowledge of the link between miRNAs and cancer
January 22, 2019 - Asthma, eczema are not barriers to active lifestyle in teenagers
January 22, 2019 - Genetic changes may predict likelihood of relapse in breast cancer patients
January 22, 2019 - Antiepileptic drug use by people with Alzheimer’s disease linked to accumulation of hospital days
January 22, 2019 - IUPUI researcher receives $2.85 million grant to find ways to improve bone strength
January 22, 2019 - Precision medicine can help keep astronauts healthy during deep space missions
January 22, 2019 - Detecting signs of neurodegeneration earlier and more accurately
January 22, 2019 - Mouse studies challenge ‘inhibition’ theory of autism
January 22, 2019 - SSB launches BIOSTAT RM TX single-use bioreactor for producing consistent quality cellular products
January 22, 2019 - Experimental drug can positively modify key characteristic behavior in FXS patients
January 22, 2019 - Low-Income Women Lack Menstrual Hygiene Supplies
January 22, 2019 - Better mouse model built to enable precision-medicine research for Alzheimer’s
January 22, 2019 - Molecular profiling of precancerous lung lesions could lead to early detection and new treatments
January 22, 2019 - Genetic factors influence where fat is stored in our bodies
January 22, 2019 - The Psychology Behind Sticking to Your New Year’s Resolutions
January 22, 2019 - Scientists aim to find genetic causes of developmental abnormalities in the vagina and uterus
January 22, 2019 - New survey reveals scale of preventative healthcare challenge in the UK
January 22, 2019 - Looming Global Crisis Means People’s Diets Must Change: Experts
January 22, 2019 - Excessive social media use is comparable to drug addiction
Neuroscientists identify a circuit that helps the brain record memories of new locations

Neuroscientists identify a circuit that helps the brain record memories of new locations

image_pdfDownload PDFimage_print
The image shows the locus coeruleus, which drives neuronal circuits of the hippocampus and enables novel contextual memory. The red staining shows norepinephrine transporter (NET)-positive cells, indicating the locus coeruleus. The green staining shows adeno-associated virus (AAV)-mediated expressions of light-sensitive inhibitory opsin, archaerhodopsin (Arch). The blue staining shows all cells in the brain stem. Credit: Akiko Wagatsuma, Tonegawa Lab

When you enter a room, your brain is bombarded with sensory information. If the room is a place you know well, most of this information is already stored in long-term memory. However, if the room is unfamiliar to you, your brain creates a new memory of it almost immediately.

MIT neuroscientists have now discovered how this occurs. A small region of the brainstem, known as the locus coeruleus, is activated in response to novel sensory stimuli, and this activity triggers the release of a flood of dopamine into a certain region of the hippocampus to store a memory of the new location.

“We have the remarkable ability to memorize some specific features of an experience in an entirely new environment, and such ability is crucial for our adaptation to the constantly changing world,” says Susumu Tonegawa, the Picower Professor of Biology and Neuroscience and director of the RIKEN-MIT Center for Neural Circuit Genetics at the Picower Institute for Learning and Memory.

“This study opens an exciting avenue of research into the circuit mechanism by which behaviorally relevant stimuli are specifically encoded into long-term memory, ensuring that important stimuli are stored preferentially over incidental ones,” adds Tonegawa, the senior author of the study.

Akiko Wagatsuma, a former MIT research scientist, is the lead author of the study, which appears in the Proceedings of the National Academy of Sciences the week of Dec. 25.

New places

In a study published about 15 years ago, Tonegawa’s lab found that a part of the hippocampus called the CA3 is responsible for forming memories of novel environments. They hypothesized that the CA3 receives a signal from another part of the brain when a novel place is encountered, stimulating memory formation.

They believed this signal to be carried by chemicals known as neuromodulators, which influence neuronal activity. The CA3 receives neuromodulators from both the locus coeruleus (LC) and a region called the ventral tegmental area (VTA), which is a key part of the brain’s reward circuitry. The researchers decided to focus on the LC because it has been shown to project to the CA3 extensively and to respond to novelty, among many other functions.

The LC responds to an array of sensory input, including visual information as well as sound and odor, then sends information on to other brain areas, including the CA3. To uncover the role of LC-CA3 communication, the researchers genetically engineered mice so that they could block the neuronal activity between those regions by shining light on neurons that form the connection.

To test the mice’s ability to form new memories, the researchers placed the mice in a large open space that they had never seen before. The next day, they placed them in the same space again. Mice whose LC-CA3 connections were not disrupted spent much less time exploring the space on the second day, because the environment was already familiar to them. However, when the researchers interfered with the LC-CA3 connection during the first exposure to the space, the mice explored the area on the second day just as much as they had on the first. This suggests that they were unable to form a memory of the new environment.

The LC appears to exert this effect by releasing the neuromodulator dopamine into the CA3 region, which was surprising because the LC is known to be a major source of norepinephrine to the hippocampus. The researchers believe that this influx of dopamine helps to boost CA3’s ability to strengthen synapses and form a memory of the new location.

They found that this mechanism was not required for other types of memory, such as memories of fearful events, but appears to be specific to memory of new environments. The connections between the LC and CA3 are necessary for long-term spatial memories to form in CA3.

“The selectivity of successful memory formation has long been a puzzle,” says Richard Morris, a professor of neuroscience at the University of Edinburgh, who was not involved in the research. “This study goes a long way toward identifying the brain mechanisms of this process. Activity in the pathway between the locus coeruleus and CA3 occurs most strongly during novelty, and it seems that activity fixes the representations of everyday experience, helping to register and retain what’s been happening and where we’ve been.”

Choosing to remember

This mechanism likely evolved as a way to help animals survive, allowing them to remember new environments without wasting brainpower on recording places that are already familiar, the researchers say.

“When we are exposed to sensory information, we unconsciously choose what to memorize. For an animal’s survival, certain things are necessary to be remembered, and other things, familiar things, probably can be forgotten,” Wagatsuma says.

Still unknown is how the LC recognizes that an environment is new. The researchers hypothesize that some part of the brain is able to compare new environments with stored memories or with expectations of the environment, but more studies are needed to explore how this might happen.

“That’s the next big question,” Tonegawa says. “Hopefully new technology will help to resolve that.”


Explore further:
How we recall the past: Neuroscientists discover a brain circuit dedicated to retrieving memories

More information:
Akiko Wagatsuma et al. Locus coeruleus input to hippocampal CA3 drives single-trial learning of a novel context, Proceedings of the National Academy of Sciences (2017). DOI: 10.1073/pnas.1714082115

Journal reference:
Proceedings of the National Academy of Sciences

Provided by:
Massachusetts Institute of Technology

Tagged with:

About author

Related Articles