NIH Logo
November 17, 2017
Digest
Study Shows How Memories Ripple Through the Brain

Using an innovative “NeuroGrid” technology, scientists showed that sleep boosts communication between two brain regions whose connection is critical for the formation of memories. The work, published in Science, was partially funded by the Brain Research through Advancing Innovative Neurotechnologies (BRAIN) Initiative.
NeuroGrid
IMAGE: MAXIPHOTO/ISTOCK

“Using new technologies advanced by the BRAIN Initiative, these researchers made a fundamental discovery about how the brain creates and stores new memories,” said Dr. Nick Langhals, program director at the National Institute of Neurological Disorders and Stroke.

A brain structure called the hippocampus is widely thought to turn new information into permanent memories while we sleep. Previous work by the new study’s senior author, New York University School of Medicine professor Dr. György Buzsáki, revealed high-frequency bursts of neural firing called ripples in the hippocampus during sleep and suggested they play a role in memory storage. The current study confirmed the presence of ripples in the hippocampus during sleep and found them in certain parts of the association neocortex, an area on the brain’s surface involved in processing complex sensory information.

“When we first observed this, we thought it was incorrect because it had never been observed before,” said Dr. Dion Khodagholy, the study’s co-first author and assistant professor at Columbia University.

Using a cutting-edge NeuroGrid system they invented, along with recording electrodes placed deeper into the brain, the researchers examined activity in several parts of rats’ brains during non-rapid eye movement (NREM) sleep, the longest stage of sleep. Their NeuroGrid consists of a collection of tiny electrodes linked together like the threads of a blanket, which is then laid across an area of the brain so that each electrode can continuously monitor the activity of a different set of neurons.

“This particular device allows us to look at multiple areas of the brain at the same time,” said Dr. Jennifer Gelinas, the study’s co-first author and assistant professor at Columbia.

The team was also surprised to find that the ripples in the association neocortex and hippocampus occurred at the same time, suggesting the two regions were communicating as the rats slept. Because the association neocortex is thought to be a storage location for memories, the researchers theorized that this neural dialogue could help the brain retain information.

To test that idea, they examined brain activity during NREM sleep in rats trained to locate rewards in a maze and in rats that explored the maze in a random fashion. In the latter group of animals, the ripples in the hippocampus and cortex were no more synchronized before exploring the maze than afterwards. In the trained rats, the learning task increased the cross-talk between those areas, and a second training session boosted it even more, further suggesting that such communication is important for the creation and storage of memories.

The group hopes to use the NeuroGrid in people undergoing brain surgery for other reasons to determine if the same ripples occur in the human brain. The researchers also plan to investigate if manipulating that neural firing in animals can boost or suppress memory formation in order to confirm that ripples are important for that process.

“Identifying the specific neural patterns that go along with memory formation provides a way to better understand memory and potentially even address disorders of memory,” said Gelinas.

New Targets Revealed for Anti-Malaria Drugs

The deadliest malaria parasite needs two proteins to infect red blood cells and exit the cells after it multiplies, a finding that may provide researchers with potential new targets for drug development, according to researchers funded by NIH. Their study appeared in Science.

Plasmodium falciparum, the species of parasite that causes the most malaria deaths worldwide, has developed drug-resistance in five countries in Southeast Asia.

In the current study, researchers sought to uncover the role of plasmepsins IX and X, two of the 10 types of plasmepsin proteins produced by P. falciparum for metabolic and other processes. They created malaria parasites that lacked plasmepsin IX or X under experimental conditions and compared them to those that had the two proeins.

The team found plasmepsin IX in rhoptries, specialized cell structures inside the parasite that help it invade red blood cells. Parasites lacking plasmepsin IX had defective rhoptries. In addition, the team observed plasmepsin X in exonemes—small vesicles (balloon-like structures) that help malaria parasites exit infected cells. The team also discovered that plasmepsin X processes an important protein called SUB1. When deprived of plasmepsin X, the parasites couldn’t process SUB1 and couldn’t infect red blood cells or exit these cells after multiplying.

The researchers also identified three experimental malaria drugs that may work by targeting plasmepsin X. One drug, called CWHM-117, has already been tested in a mouse model of malaria. The new findings may help researchers modify CWHM-117 to make it more effective. Furthermore, parasites lacking the plasmepsins could potentially be used to screen candidate drugs to identify additional anti-malaria compounds.

Study Identifies Brain Patterns Underlying Momsí Responses to Infant Cries

Infant cries activate specific brain regions related to movement and speech, according to an NIH study of mothers in 11 countries. The findings, led by researchers at NICHD, identify behaviors and underlying brain activities that are consistent among mothers from different cultures. Understanding these reactions may help in identifying and treating caregivers at risk for child maltreatment and other problematic behaviors.

Mon huging her baby
IMAGE: NIDERLANDER/ISTOCK

The study team conducted a series of behavioral and brain imaging studies using functional magnetic resonance imaging (fMRI). In a group of 684 new mothers in Argentina, Belgium, Brazil, Cameroon, France, Israel, Italy, Japan, Kenya, South Korea and the United States, researchers observed and recorded 1 hour of interaction between the mothers and their 5-month-old babies at home. The team analyzed whether mothers responded to their baby’s cries by showing affection, distracting, nurturing (like feeding or diapering), picking up and holding or talking. Regardless of which country they came from, mothers were likely to pick up and hold or talk to their crying infant.

Through fMRI studies of other groups of women, the team found that infant cries activated similar brain regions in new and experienced mothers: the supplementary motor area, which is associated with the intention to move and speak; the inferior frontal regions, which are involved in the production of speech; and the superior temporal regions that are linked to sound processing.

Overall, the findings suggest that mothers’ responses to infant cries are hard-wired and generalizable across cultures. The study also builds upon earlier work showing that women’s and men’s brains respond differently to infant cries.

back to top of page