Nature sub-journal: Neurons on the same day are more likely to "advance and retreat"

Neurons in the hippocampus

The brain's hippocampus is known to play a vital role

Recently, in a new study published in Nature Neuroscience, a team of researchers from the Grossman School of Medicine at New York University found that whether awake or asleep, neurons with the same "birthday" showed unique synergistic activity
in different brain states throughout the adulthood of mice compared to hippocampal neurons that were "born" on different days.

The study revealed functional characteristics of sequential neurogenesis during embryonic development that influence the patterns
of activity of the adult hippocampus.

This finding promises to improve the way existing research into neurodevelopmental disorders is done
.

The study suggests that the brain may use the gradual formation of neuronal layers to build neural templates, much like "Lego bricks", matching each new experience to an existing template when forming memories, rather than creating a new memory
from scratch.

This suggests that developmental processes use neurons formed orderly during pregnancy to form synergistic microfolds in the hippocampus that encode
similar memories.

This rule of neural circuit assembly tells us that brain cells with the same birthday are more likely to "go back and forth," that is, to encode memories together and experience failures
together.

This means that the "birth" date of neurons may be associated
with diseases such as autism spectrum disorder and Alzheimer's.

As the number of neurons that form changes at different times, the developing brain is more likely to be harmed
by viral infections, toxins, or alcohol at certain stages of pregnancy.

In the new study, the team used the method of electroporation of the intrauterine hippocampus to transfer DNA into dividing neurons in mice's uterus to track neuronal activity
from a specific date of birth to adulthood.

These DNA expressed pyramidal neurons in the CA1 region that were labeled at the same time, similar to barcodes
.

Using this labeling method, researchers can study hippocampal neurons
throughout the animal's life cycle.

They found that neurons of the same date of birth tend to "co-fire," characterized by synchronous fluctuations in positive and negative charges, which together transmit electrical signals
.

There are far
more neurons born at 15.
5 days of the embryo than neurons born earlier or later.

One of the possible reasons for the co-firing is that neurons with the same date of birth share neuronal connections
, the researchers said.

In the hippocampus of mouse embryos, groups of neurons with the same birthday (pink) and groups of neurons with different birthdays (blue) Past studies have shown that hippocampal activity can be described in terms
of patterns of collective neuronal activity during wake and sleep.

For example, during sleep, when daily memories are consolidated for long-term memory storage, hippocampal neurons release a periodic pulse
called a "spike ripple.
"
This activity is named after
the shape of the image captured by the electroencephalogram (EEG).

The new findings suggest that neurons formed on the same day become part of the same collaborative whole to participate in the same spike wave activity and represent the same memory
.

These relationships, along with the preset templates they encode, have important implications
for hippocampus function.

The researchers believe that the day on which hippocampal neurons are born strongly influences the neuron's performance and how they collectively signal throughout life
.

Therefore, this study may change the way neurodevelopmental disorders are studied
.

In traditional approaches, researchers look at neurodevelopmental disorders through a molecular or genetics perspective rather than a developmental perspective
.

Next, the team says, they will conduct more experiments to identify genes that are active in neurons with the same birthday in different brain regions and test their role
in memory formation and behavior.

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