For memory, brain relies on newbie neurons

STONY BROOK (US) / U. TORONTO (CAN) — Newly generated neurons are crucial for normal learning and memory, even in the aging adult brain, new research shows.

The functional role of newborn neurons in the brain is controversial, but the study, published in the journal Nature Neuroscience, shows that silencing newborn neurons impairs memory retrieval.

Previous research by the study’s lead investigator Shaoyu Ge, assistant professor of neurobiology and behavior at Stony Brook University demonstrated that newborn neurons form connections with existing neurons in the adult brain.

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To help determine the role of newborn neurons, Ge and colleagues devised a new optogenetic technique to control newborn neurons and test their function in the hippocampus, one of the regions of the brain that generates new neurons, even in the adult aging brain.

“Significant controversy has surrounded the functional role of newborn neurons in the adult brain,” Ge says.

“We believe that our study results provide strong support to the idea that new neurons are important for contextual fear memory and spatial navigation memory, two essential aspects of memory and learning that are modified by experience.

“Our findings could also shed light on the diagnosis and treatment of conditions common to the adult aging brain, such as dementia and Alzheimer’s disease.”

The findings may help specifically to advance research on cell-replacement therapies being investigated for neurological diseases of the brain affecting memory.

In the study, Ge and colleagues used a retroviral tool to deliver optogenes: genes that are engineered to express proteins that form channels responsive to light stimulation. Using their created opto-retrovirus, researchers labeled a cohort of newborn neurons that they could control with light illumination. By doing this, the team conducted an in-depth exploration of the circuit and behavioral functions of newborn neurons in the adult mouse brain.

The researchers first determined when the neurons were “ready” in the hippocampus, which is an important addition to findings published earlier this year in Nature Neuroscience.

Then they silenced the activity of neurons of different ages and found that by silencing four-week-old neurons, an age known to be more responsive to change than existing neurons, but not older or younger neurons, memory retrieval was impaired in tasks known to depend on the functions of the hippocampus.

Regarding the newborn neuron controlling method, Ge says the tool and approach used in the study can be applied to other circuit and behavioral studies to access the functional contributions of newborn neurons in the adult brain.

Researchers from the University of Toronto contributed to the study.

Source: Stony Brook University