‘Lightning bolts’ in the brain reveal how the brain encodes and stores information without disrupting previously acquired memories

Could help explain the underlying neural circuit problems in disorders like autism and schizophrenia
April 1, 2015

Images of dendrites of L5 pyramidal neurons in motor cortex during resting (top) and forward running (FWR) (below). Running-induced calcium-ion transients were visible over long dendritic segments (yellow arrowheads). (credit: Joseph Cichon & Wen-Biao Gan/Nature)

Researchers at NYU Langone Medical Center have captured images of dendrite nerve branches that show how mice brains sort, store, and make sense out of information during learning.

In a study published online in the journal Nature March 30, the NYU Langone neuroscientists tracked neuronal activity in dendritic nerve branches as the mice learned motor tasks such as how to run forward and backward on a small treadmill.

They found that the generation of calcium ion spikes — which appeared in screen images as tiny “lightning bolts” in these dendrites — was tied to strengthening or weakening connections between neurons, hallmarks of learning new information.

“We believe our study provides important insights into how the brain deals with vast amounts of information continuously as the brain learns new tasks,” says senior study investigator and neuroscientist Wen-Biao Gan, PhD.

How the brain stores new information non-destructively

Gan, a professor at NYU Langone and its Skirball Institute of Biomolecular Medicine, says, “We have long wondered how the brain can store new information continuously throughout life without disrupting previously acquired memories. We now know that the generation of calcium spikes in separate branches of nerve cells is critical for the brain to encode and store large quantities of information without interfering with each other.”

NYU Langone | Lightning Bolts in the Brain Show Learning in Action

They found that learning motor tasks such as running forward and backward induced different patterns of lightning bolt-like activity in the dendrites, triggering a chain-like reaction, which changed the strength of connections between neurons.

They also identified a unique cell type in the brain that controlled where the lightning bolts were generated. When these “somatostatin-expressing interneurons” were turned off, lightning bolt patterns in the brain were disrupted, and as a result, the animal lost the information it had just learned.

Lead study investigator Joseph Cichon, a neuroscience doctoral candidate at NYU Langone, says their discoveries could have important implications for explaining the underlying neural circuit problems in disorders like autism and schizophrenia. Cichon says the team’s next steps are to see if calcium ion spikes are malfunctioning in animal models of these brain disorders.

Funding support for the study was provided by the National Institutes of Health.

Abstract of Branch-specific dendritic Ca2+ spikes cause persistent synaptic plasticity

The brain has an extraordinary capacity for memory storage, but how it stores new information without disrupting previously acquired memories remains unknown. Here we show that different motor learning tasks induce dendritic Ca2+ spikes on different apical tuft branches of individual layer V pyramidal neurons in the mouse motor cortex. These task-related, branch-specific Ca2+spikes cause long-lasting potentiation of postsynaptic dendritic spines active at the time of spike generation. When somatostatin-expressing interneurons are inactivated, different motor tasks frequently induce Ca2+ spikes on the same branches. On those branches, spines potentiated during one task are depotentiated when they are active seconds before Ca2+ spikes induced by another task. Concomitantly, increased neuronal activity and performance improvement after learning one task are disrupted when another task is learned. These findings indicate that dendritic-branch-specific generation of Ca2+ spikes is crucial for establishing long-lasting synaptic plasticity, thereby facilitating information storage associated with different learning experiences.