“Plasticity in mental health: A network theory“
- High plasticity leads to a greater susceptibility to change brain and behavior according to context.
- Plasticity is not beneficial per se but its value must be estimated according to the context.
- Resilience arises from the interaction between plasticity levels and the context.
- Network theory allows for an operationalization and formal measure of plasticity.
Plasticity is the ability to modify brain and behavior, ultimately promoting an amplification of the impact of the context on the individual’s mental health. Thus, plasticity is not beneficial per se but its value depends on contextual factors, such as the quality of the living environment. High plasticity is beneficial in a favorable environment, but can be detrimental in adverse conditions, while the opposite applies to low plasticity. Resilience and vulnerability are not univocally associated to high or low plasticity. Consequently, individuals should undergo different preventive and therapeutic strategies according to their plasticity levels and living conditions.
An operationalization of plasticity relying on network theory is proposed: the strength of the connection among the network elements defining the individual, such as its symptoms, is a measure of plasticity.
This theoretical framework represents a promising tool to investigate research questions related to changes in neural structure and activity and in behavior, and to improve therapeutic strategies for psychiatric disorders, such as major depression.
Finally, the theory proposed here may contribute to building a new conceptual view of plasticity as emerging from the interaction of brain and behavioral elements and not residing in any specific brain element or
behavioral activity, in line with the increasing relevance of the study of the brain according to a complex approach that involves both upward and downward causation models.
The strength of the system network is a measure of system plasticity, i.e. of its susceptibility to change its state.
(a) When a network is weakly connected, (b) an external stimulus (e.g. stress) produces an immediate change in the system state (healthy state) that is proportional to the stimulus magnitude.
However, (d) when the elements are strongly connected, (e) the change in the system state is neither immediate nor proportional. Even if the magnitude of the external stimulus constantly rises, the system is stuck in its starting state. Only following a very large increase/decrease of the stimulus magnitude, the system state is abruptly modified. Thus, weakly and strongly connected networks have to be considered a proxy of, respectively, high and low plasticity.
This can be translated into the likelihood to switch from a pathological to a healthy state or vice versa. For instance, (c) individuals characterized by weakly connected networks, and thus by high plasticity, easily switch between the two states. By contrast, (f) individuals characterized by strongly connected networks, and thus by low plasticity, tend to be stuck
in one of the two states.
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