Led by researchers from NYU Grossman
School of Medicine, the new study on the brains of mice developing in the womb
found that brain cells (neurons) with the same birthdate showed distinct
connectivity and activity throughout the animals’ adult lives, whether they
were asleep or awake.
Published online August 22 in Nature
Neuroscience, the findings suggest that
evolution took advantage of the orderly birth of neurons — by gestational day —
to form localized microcircuits in the hippocampus, the brain region that forms
memories. Rather than attempting to create each new memory from scratch, the
researchers suggest, the brain may exploit the stepwise formation of neuronal
layers to establish neural templates, like “Lego pieces,” that match each new
experience to an existing template as it is remembered.
These rules of circuit assembly would
suggest that cells born together are more likely to encode memories together,
and to fail together, potentially implicating neuronal birthdate in diseases
like autism and Alzheimer’s, say the authors. With changes to the number of
cells born at different days, the developing brain may be more vulnerable on
some gestational days to viral infections, toxins, or alcohol.
“Our study’s results suggest that which
day a hippocampal neuron is born strongly influences both how that single cell
performs, and how populations of such cells signal together throughout life,”
says senior study author György Buzsáki, MD, PhD, the Biggs Professor in the
Department of Neuroscience and Physiology at NYU Langone Health. “This work may
reshape how we study neurodevelopmental disorders, which have traditionally
been looked at through a molecular or genetic, rather than a developmental,
lens,” says Buzsáki, also a faculty member in the Neuroscience Institute at NYU
Langone.”
New
Understanding
The current study’s innovation rests on
tracking the activity of neurons of a given birthdate into adulthood. To
accomplish this, the researchers relied on a technique that allowed them to
transfer DNA into cells that were undergoing division into neurons in the womb.
The DNA expressed markers that tagged brain cells that were born on same day,
akin to a barcode. This labeling method then enabled the researchers to study
these neurons in the adult animal.
Using a combination of techniques, the
new study found that neurons of the same birthdate tend to “co-fire” together,
characterized by synchronized swings in their positive and negative charges,
allowing them to transmit electrical signals collectively. A likely reason for
the co-firing, say the authors, is that neurons with the same birthdate are
connected via shared neurons.
Past work had shown that activity in the
hippocampus can be described in terms patterns of collective neuronal activity
during waking and sleep. During sleep, for instance, when each day’s memories
are consolidated for long-term memory storage, hippocampal neurons engage in a
cyclical burst of activity called the “sharp wave-ripple,” named for the shape
it takes when captured graphically by EEG, a technology that records brain
activity with electrodes.
“Our results show that neurons born on
the same day become part of the same cooperating assemblies, and participate in
the same sharp wave-ripples and represent the same memories,” says first author
Roman Huszár, a graduate student in Buzsáki’s lab. “These relationships, and
the pre-set templates they encode, have a key implication for hippocampal
function: the storage of a memory about a place or event.”
Moving forward, the team plans additional experiments to identify the genes active in the same birthdate neurons in different brain regions, and to test their role in memory formation and behavior.
Source: https://nyulangone.org/news/brain-cells-born-together-wire-fire-together-life
Journal article: https://www.nature.com/articles/s41593-022-01138-x
Source: Brains
cells born together wire and fire together for life – Scents of Science
(myfusimotors.com)
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