Traumatic memories can alter the brain connections

Associative learning, which includes classical conditioning, is one of the simplest types of learning and has been studied intensively over the past century.

Researchers found that fear conditioning led to learning-specific changes in neuronal-network activity in the dorsal part of the medial prefrontal cortex of mice. This study in Nature Communications demonstrates the use of combined methods for detailed visualization of the dynamics of neural networks, and describes techniques that could be used to uncover additional information about the neurological changes associated with learning and memory.

The research team used longitudinal two-photon imaging and various computational neuroscience techniques to determine how neural activity changes in the mouse prefrontal cortex after learning in a fear-conditioning paradigm. Prefrontal neurons behave in a highly complex manner, and each neuron responds to various sensory and motor events.

Importantly, the researchers uncovered direct evidence that associative memory formation was accompanied by a novel associative connection between originally distinct networks, i.e., the conditioned stimulus (CS, e.g., tone) network and the unconditioned stimulus (US, e.g., fearful experience) network.

"We successfully detected a neural population that encodes fear memory," says Agetsuma. "Our analyses showed us that fear conditioning induced the formation of a fear-memory neural network with 'hub' neurons that functionally connected the memory neurons."

Reference: Masakazu Agetsuma, Issei Sato, Yasuhiro R. Tanaka, Luis Carrillo-Reid, Atsushi Kasai, Atsushi Noritake, Yoshiyuki Arai, Miki Yoshitomo, Takashi Inagaki, Hiroshi Yukawa, Hitoshi Hashimoto, Junichi Nabekura, Takeharu Nagai. Activity-dependent organization of prefrontal hub-networks for associative learning and signal transformation. Nature Communications, 2023; 14 (1) DOI: 10.1038/s41467-023-41547-5