**1. Introduction**

Forgetting or forgetfulness is not only a passive activity of neurons but also an active process, in which, specific brain areas play role in the neural circuits of temporal and frontal lobes to eliminate information that does not need to be stored in memory. Its importance is sustained by the fact of avoiding saturation of the neural circuitry; knowledge that could be irrelevant or shallow for the diary living activities or in its case, accumulation of chronic unnecessary skills.

This chapter is constructed on the basic principles of neuroplasticity and memory, in order to understand how the information is obtained from the senses and then the perception that might be needed to be kept in the brain, depending on its modality. After this point, which is the molecular and cellular mechanism used by the neurons to filter the relevant juxtaposing the purposeless. It is being added to the clinical feature of neurological illness to distinguish amnesia from forgetting. It will be expressed the future of treating patients that need to ameliorate forgetfulness in their daily life.

Although many new areas are being researched, others are kept apart from the interest of professionals. That is why this book chapter is presented, aiming to inform the new physiological mechanisms that have been described in the forgetting process, so as its relationship with neuroplasticity. Also, there will be an in-depth explanation of some pathologies and affections that trigger this neurophysiological response.
