Neuronal activity refers to the electrical and chemical signals produced by neurons in the brain and nervous system. This activity is critical for information processing, communication between neurons, and ultimately behavior and cognition. Researchers study neuronal activity using techniques such as electrophysiology, calcium imaging, and functional magnetic resonance imaging (fMRI) to understand how neurons communicate, form networks, and contribute to various functions such as perception, memory, and decision-making. By studying neuronal activity, researchers can gain insights into the inner workings of the brain and its role in health and disease.