With progress in neurosciences, neuroimaging and brain stimulation techniques, mental illnesses are now being seen as development anomalies at the molecular-structural level of synapses, resulting in abnormal cross wiring in areas responsible for complex cognitive and emotional processing. These include the multimodal association cortices situated in the prefrontal lobes, the insula in the temporal lobes, midline cortical structures, and their connections to the thalamus, amygdala and the basal ganglia. Three key networks have been identified which are considered the brain hubs for complex perceptual, emotional and behavior processing as well as introspection, theory of mind and self-awareness; namely the salience network (SN), the central executive network (CEN) and the default mode network (DMN). They function in an interconnected manner and involve in higher information processing of the entire internal and external milieu of the organism to determine the behavior strategies to be adopted. A triple network model of aberrant saliency mapping and cognitive dysfunction in psychopathology has been put forward recently and an attempt is being made to understand core cognitive networks and their dysfunction across multiple disorders including schizophrenia, depression, anxiety, autism and dementia. Against this background, the author would like to take the triple network dysfunction model a step further to hypothesize the following. 1. All or some of the three core networks (CEN, SN & DMN) are affected variably in psychiatric disorders, the severity and the nature of the clinical symptoms depending upon the degree of damage and the number of networks that are dysfunctional and whether that dysfunction is reversible or permanent. For example, in a condition like schizophrenia, all three networks would more or less be affected giving rise to plethora of symptoms like executive deficits, negative symptoms, abnormal salience and mood states. In milder conditions like anxiety and depressive disorders, on the other hand, the dysfunction is of a lesser degree and reversible. 2. These networks are the final common pathway through which a variety of internal or environment insults to the brains may act, the degree of damage and reversibility being determined by the critical period of brain development in which these occur. 3. The harmonious functioning of these core networks is what gives rise to the complex phenomenon of the mind in the brain.
Copyright © 2019. Published by Elsevier Ltd.