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Category: neuroscience – Page 12

How the auditory cortex syncs with behavior to help the brain become a better listener

When we are engaged in a task, our brain’s auditory system changes how it works. One of the main auditory centers of the brain, the auditory cortex, is filled with neural activity that is not sound-driven—rather, this activity times the task, each neuron ticking at a different moment during task performance.

Researchers at Hebrew University have discovered how this happens. The study published in Science Advances, led by Prof. Israel Nelken from the Edmond and Lily Safra Center for Brain Sciences (ELSC) and the Institute of Life Sciences, is based on the Ph.D. research of Ana Polterovich, with contributions from Alex Kazakov, Maciej M. Jankowski, and Johannes Niediek.

They found that when we are engaged in the task, neurons in the brain’s show large bursts of activity that aren’t caused directly by sounds. Instead, these “” are tied to specific moments in a task, suggesting that the auditory cortex is deeply in sync with behavior.

Deep sleep supports memory via brain fluid and neural rhythms, research finds

Researchers led by Masako Tamaki at the RIKEN Center for Brain Science in Japan report a link between deep sleep and cerebrospinal fluid, the clear liquid that surrounds and supports the brain and spinal cord. Published in Proceedings of the National Academy of Sciences, the study demonstrates how changes in cerebrospinal fluid signals during sleep—as measured by MRI—are time-locked to slow brain waves and other neural events.

These findings offer a clue as to why stable sleep is important for normal brain function, particularly within the brain network that controls learning and memory.

Why do we sleep? Scientists think that sleep is important for consolidating memories and removing waste from the brain that accumulates as a result of brain activity while we are awake.

Surprising gene mutation in brain’s immune cells linked to increased Alzheimer’s risk

In a study published in Neuron, a research team at the Department of Neurology at Massachusetts General Hospital, aimed to understand how immune cells of the brain, called microglia, contribute to Alzheimer’s disease (AD) pathology. It’s known that subtle changes, or mutations, in genes expressed in microglia are associated with an increased risk for developing late-onset AD.

The study focused on one such mutation in the microglial gene TREM2, an essential switch that activates microglia to clean up toxic amyloid plaques (abnormal protein deposits) that build up between in the brain. This mutation, called T96K, is a “gain-of-function” mutation in TREM2, meaning it increases TREM2 activation and allows the gene to remain super active.

The researchers explored how this mutation impacts microglial function to increase risk for AD. The team generated a mutant mouse model carrying the mutation, which was bred with a mouse model of AD to have brain changes consistent with AD. They found that in female AD mice exclusively, the mutation strongly reduced the capability of microglia to respond to toxic amyloid plaques, making these cells less protective against brain aging.

Astrocytes are superstars in the game of long-term memory

Why are we able to recall only some of our past experiences? A new study led by Jun Nagai at the RIKEN Center for Brain Science in Japan has an answer. Surprisingly, it turns out that the brain cells responsible for stabilizing memories aren’t neurons. Rather, they are astrocytes, a type of glial cell that is usually thought of as a role player in the game of learning and memory.

Published in Nature, the study shows how emotionally intense experiences like fear biologically tag small groups of astrocytes for several days so that they can re-engage when a mouse recalls the experience. It is this repeated astrocytic engagement that stabilizes memories.

Astrocytes have traditionally been thought to have a supporting role in the brain, literally. But when it became clear that engrams—the actual traces that exist in neurons—cannot alone account for stabilized, , Nagai and his team turned to astrocytes for a solution.

Disconnected cerebral hemisphere in epilepsy patients shows sleep-like state during wakefulness

Sleep-like slow-wave patterns persist for years in surgically disconnected neural tissue of awake epilepsy patients, according to a study published in PLOS Biology by Marcello Massimini from Universita degli Studi di Milano, Italy, and colleagues.

The presence of slow waves in the isolated hemisphere impairs consciousness; however, whether they serve any functional or plastic role remains unclear.

Hemispherotomy is a used to treat severe cases of epilepsy in children. The goal of this procedure is to achieve maximal disconnection of the diseased neural tissue, potentially encompassing an entire hemisphere, from the rest of the brain to prevent the spread of seizures.

Men experience more brain atrophy with age despite women’s higher Alzheimer’s risk

Women are far more likely than men to end up with Alzheimer’s disease (AD). This may, at least partially, be due to women’s longer average lifespans, but many scientists think there is probably more to the story. It would be easy to surmise that the increased risk is also related to differences in the way men’s and women’s brains change as they age. However, the research thus far has been unclear, as results across different brain regions and methods have been inconsistent.

Now, a new study, published in Proceedings of the National Academy of Sciences, indicates that it’s men who experience greater decline in more regions of the as they age. Researchers involved in the study analyzed 12,638 brain MRIs from 4,726 cognitively healthy participants (at least two scans per person) from the ages of 17–95 to find how age-related changes occurred and whether they differed between men and women.

The results showed that men experienced declines in cortical thickness and in many regions of the brain and a decline in subcortical structures in older age. Meanwhile, women showed greater decline only in a few regions and more ventricular expansion in older adults. So, while differences in brain aging between the sexes are apparent, the cause of increased AD prevalence in women is still a bit mysterious.

A ‘flight simulator’ for the brain reveals how we learn—and why minds sometimes go off course

Every day, your brain makes thousands of decisions under uncertainty. Most of the time, you guess right. When you don’t, you learn. But when the brain’s ability to judge context or assign meaning falters, thoughts and behavior can go astray. In psychiatric disorders ranging from attention-deficit/hyperactivity disorder to schizophrenia, the brain may misjudge how much evidence to gather before acting—or fail to adjust when the rules of the world change based on new information.

“Uncertainty is built into the brain’s wiring,” says Michael Halassa, a professor of neuroscience at Tufts University School of Medicine. “Picture groups of neurons casting votes—some optimistic, some pessimistic. Your decisions reflect the average.” When that balance skews, the brain can misread the world: assigning too much meaning to random events, as in schizophrenia, or becoming stuck in rigid patterns, as in obsessive-compulsive disorder.

Understanding those misfires has long challenged scientists, says Halassa. “The brain speaks the language of single neurons. But fMRI—the tool we use to study brain activity in people—tracks blood flow, not the electrical chatter of individual brain cells.”

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