The study by Sadegh Nabavi et al. investigates the causal link between synaptic plasticity and memory formation, specifically focusing on long-term potentiation (LTP) and long-term depression (LTD). The researchers used fear conditioning in rats to demonstrate that LTD and LTP can inactivate and reactivate a memory, respectively. They employed optogenetics to deliver LTD and LTP to the auditory inputs targeting the amygdala, a brain region crucial for fear conditioning. After conditioning, LTD inactivated the memory of a foot-shock, while subsequent LTP reactivated it. The study also confirmed that LTP restored the memory formed by LTD inactivation, supporting the idea that LTP reactivates the memory that was formed by LTD inactivation. Additionally, the researchers found that LTP alone did not produce a conditioned response in naïve animals, suggesting that specific potentiation onto a subset of inputs is necessary for memory formation. The findings strengthen the causal relationship between synaptic plasticity and memory formation, providing a detailed mechanism for how memories are encoded and recalled.The study by Sadegh Nabavi et al. investigates the causal link between synaptic plasticity and memory formation, specifically focusing on long-term potentiation (LTP) and long-term depression (LTD). The researchers used fear conditioning in rats to demonstrate that LTD and LTP can inactivate and reactivate a memory, respectively. They employed optogenetics to deliver LTD and LTP to the auditory inputs targeting the amygdala, a brain region crucial for fear conditioning. After conditioning, LTD inactivated the memory of a foot-shock, while subsequent LTP reactivated it. The study also confirmed that LTP restored the memory formed by LTD inactivation, supporting the idea that LTP reactivates the memory that was formed by LTD inactivation. Additionally, the researchers found that LTP alone did not produce a conditioned response in naïve animals, suggesting that specific potentiation onto a subset of inputs is necessary for memory formation. The findings strengthen the causal relationship between synaptic plasticity and memory formation, providing a detailed mechanism for how memories are encoded and recalled.