How Fear Restructures the Mouse Brain

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"... In a study published in Cell Reports on August 2, researchers ... used a combination of deep learning algorithms and high-resolution electron microscopy to map out how frightful experiences rearrange brain connections. They found that when mice learn to fear the sound of a buzzer, neurons in their hippocampus form more connections with other neurons downstream and shuttle more mitochondria to synaptic sites. This change in neural connectivity increases the information storage capacity of the brain without increasing synaptic density.  ...
The study coauthors imaged the mouse brains using a technique called serial-section Electron Microscopy (ssEM), which shoots beams of high-speed electrons at thin slices of tissue to generate ultra-high-resolution images. This allows researchers to visualize the smallest of structures. ..."

From the abstract:

"... We thus developed a region-CNN [Convolutional Neural Network]-based deep learning method to identify, segment, and reconstruct synapses and mitochondria to explore the structural plasticity of synapses and mitochondria in the auditory cortex of mice subjected to fear conditioning. Upon reconstructing over 135,000 mitochondria and 160,000 synapses, we find that fear conditioning significantly increases the number of mitochondria but decreases their size and promotes formation of multi-contact synapses, comprising a single axonal bouton and multiple postsynaptic sites from different dendrites. Modeling indicates that such multi-contact configuration increases the information storage capacity of new synapses by over 50%. With high accuracy and speed in reconstruction, our method yields structural and functional insight into cellular plasticity associated with fear learning."

How Fear Restructures the Mouse Brain | The Scientist Magazine®

Fear memory-associated synaptic and mitochondrial changes revealed by deep learning-based processing of electron microscopy data (open access)