"The neocortex is the brain area that is most expanded in the human brain. It is thought that neocortical function underlies the remarkable adaptive and associative learning skills of mammals. Learning-dependent neocortical plasticity is supposed to rely on subtle changes in the spatial pattern and level of neuronal activity that likely depend on connectivity rearrangement through synapses turnover and/or activity-dependent strengthening and weakening of pre-established synapses. However, whether this structural-functional cascade occurs in higher cognitive frontal areas during associative stimulus learning is currently not known. By combining in vivo two-photon long-term structural imaging of dendritic spines, large-scale neuronal calcium imaging, and whole-cell recording in the behaving animal, we aim at understanding how the formation and extinction of associative fear memories are implemented by neuronal circuits in rodent frontal association cortex (FrA). Understanding of how different neurons in higher cortical areas modulate the structure of their connections in response to learning, and how this would alter the cortical processing is a key to understand how we store information and acquire new skills, and potentially help to advance the design of new strategies toward memory enhancement and neuronal repair in a wide range of brain diseases."