**5. Concept of forgetting or forgetfulness**

Forgetting is defined as the loss of memory or the failure of the brain to remember. It is the fact that something concrete or a special person, is not present in the mind of a subject. Although he or she might have known them well previously. It is interesting that forgetfulness is a synonym for forgetting in a colloquial or scientific language, based on the ideas of Della Sala and Cubelli [33]. Nevertheless, forgetting could be more punctual to the "fact of forget", and forgetfulness is the process and state of not remembering [34].

#### **5.1 Objectives of forgetting**

It is relevant for the brain and the mind to experience forgetfulness. In the same way a person could be memorizing events, skills, situations, and circumstances in a

### *Neurophysiology Involved in Neuroplasticity: Mechanisms of Forgetting DOI: http://dx.doi.org/10.5772/intechopen.105129*

natural process; it is necessary for a similar path to forget all the things that are not essential in the activity's life. Indeed, one cannot exist if the other one is abolished. It erases the shallow and specific things dispensable to work. This allows the new experience or knowledge, even though opening the gate for creativity or innovation, inclusively, it could be considered a paradoxical effect because one person forgets insignificant information and could store an important one [35, 36].

Furthermore, forgetting helps to ameliorate traumatic or anxious situations that could be dangerous to mental health. This indicates a capability to grow and promote personality maturation coupled with emotional intelligence.

#### **5.2 Microglia and macroglia in forgetting**

The microglia cells are the caregivers of the neurons because they support, nourish, and attack the estrange and harmful cells. This last activity is based on the activation of the complement system: for the attack including C1q, C3, and CR3; and for the cell, preservation uses CD47 (cluster of differentiation 47), SIRPα (signalregulatory protein), and CX3CR (chemokine receptor 1). Indeed, these components of complement resting the microglia to prune synapsis during neural activity and plasticity [37]. Neuroplasticity involves the stability of the long-term potential (LTP), a neural mechanism based on the dependent- Ca++ gates to produce the learning and memory phenomena [38]. It is in the same direction the memory needs the microglia to consolidate that the use of complement in the inverse sense to get forgetting, undoubtedly with the use of microglia. In a double mechanism with gradual and activity-dependent, the retraction of synapsis mediated by the glia contributes to forgetting [39] (**Figure 3**).

Although there is no substantial evidence of the participation of macroglia (*i.e.,* oligodendrocytes and astrocytes) in forgetting mechanisms [40, 41], further investigation must be required. Based on the proposition that astrocytes play an important role in neurotransmission uptake and neural guidance, so as their immunological properties as cells [42].

#### **Figure 3.**

*It is shown the cellular mechanism of forgetting. Preservation and pruning in the neuron (a) and the micro/ macroglia (b). V↑↓Ca2+= Regulation in voltage-gated calcium channels; CD47 = Cluster of Differentiation 47, SIRPα = Signal-Regulatory Protein Alpha, CX3CR = Chemokine Receptor 1; C1q = Complement component 1q, C3 = Complement component 3, CR3 = Complement receptor 3 [37].*
