**2. From brain activities to mental activities**

Not only *bío* but also *psyche*: the great challenge of neuroscience is to understand behavior and thought.

Although humans have wondered about the control of behavior for thousands of years, only fairly recently has a mechanistic view of the brain taken hold [4, 5]. The concept of *localization of function* was an important milestone for behavioral neuroscience. Today we know that the contemporaneous functional modulation of different cerebral areas varies in a predictable way depending on what a subject is doing. Thanks to modern neuroimaging and a more carefully validated understanding of human cognition, a detailed view of the brain organization is now emerging. Modular systems are outdated; the network approach is the current one [2].

One of the main topics of discussion in the twentieth century was whether *mental activities*—such as thought, emotions, self-awareness, and will—are functions different from *brain activities*, such as the movement of a limb, the perception of a color, etc., or if they also represent functional expressions of the brain neurons. Mental and cerebral activities would seem to be the unique and indivisible expression of the activities of the neuronal and glial elements that make up the brain organ. Although the expression is different in quality and in the ways in which it manifests itself, both activities are due to a single mechanism by which neurons communicate with each other and with the rest of the body [2]. The neural circuits and their realization are encoded in the animal genome, while the environmental stimuli play a fundamental role for the definitive realization of the synaptic connections.

Neurons, organized in ganglia, complex structures, and networks, process nerve impulses, memorize them, and emit behavioral responses. It is probable that once we fully understand these first two levels—that of the functions of the individual neurons and that of the activities of the neural networks—we will arrive at the elucidation of the type of circuits (or nervous activities) with which subjects are able to decide a specific motor act or a reminiscent act and the mechanisms by which the brain, at the same time as processing sensory inputs, makes subjects aware of all these operations.

Only today, we begin to have information of fundamental importance on the nature of mental processes such as consciousness, will, social cognition, and enormously complex problems that constitute the core of the third level of brain functions.
