## 4 Common/Unifying Theoretical-Conceptual Framework
### qEEG Phenotype, Personality Traits, and Norm-Pathology Continuum  
The above review (Section 4.2) demonstrates that variability in personality traits and their associated characteristics of qEEG phenotypes are expressed in both healthy and pathological conditions. This suggests that personality traits and neuropsychopathology are not distinct entities, but rather, they manifest along a unified continuum of functioning, where mental diseases can be considered to fall along multiple continuous trait dimensions, with traits (and corresponding characteristics of qEEG phenotype) ranging from normal to extreme (pathological). Here, neuropsychopathology is considered in terms of dysfunctions of various kinds and degrees. In other words, neuropsychopathology is the _over_-expression or _under_-expression of personality traits and the associated characteristics of qEEG phenotypes that are otherwise moderately expressed in healthy conditions. Such a view assumes a _dimensional_ approach to neuropsychopathology, which considers the full range of variation, from normal to abnormal functioning, where both extremes of a dimension may be considered 'abnormal' [515]. For example, when anxiety increases beyond an optimal level, (a) one's perceptual field narrows and attention to task-relevant cues fails [693], (b) the ability to store and retrieve task-relevant information deteriorates [694,695], and (c) distracting and task-irrelevant thoughts increase [696]. In its extreme form, it is associated with anxiety disorders. On the opposite end of the dimension, a complete lack of anxiety may be associated with aggressive or psychopathic behavior. Consider another example from [697] (p. 116): \"[...], persons that fall in the high-end of sociability dimension, have positive emotional and high approach-motivation tendencies are also high in the novelty-seeking trait and low in the harm-avoidance trait (Davies, 2012; Eysenck, 1990). Such people are likely to find extravagance, novelty, and excitement motivating but will be relatively insensitive to the feelings of others, punishment for breaching rules, or the possibility of failure (Cavanagh, 2005)\" (references in this citation can be found in [697]). In the extreme, it may be associated with mania, narcissism, psychopathy, substance abuse, excessive venturesomeness (excitement-seeking), risk-taking, grandiosity, exhibitionism, and manipulativeness [635]. On the opposite end of the dimension, lack of sociability may be associated with emotional tension or depression. Considering a dimensional approach to neuropsychopathology, the following _functional continuum_, through normality (health) and mental disorders (psychopathology), can be proposed (Figure 5). Figure 5: The norm-pathology continuum. Here, the focus is on the expression of the characteristics of qEEG phenotypes (neural mechanism) over a continuous range. A corresponding mental characteristic that is linked to a particular qEEG phenotype (or its features) would also show a range of expression. Importantly, 'functionality' is the degree to which the individual is able to function, given various degrees of expression of the mental and associated qEEG phenotype's characteristics [519; 582]. Hence, the degree of functionality associated with the expression of the mental characteristic corresponds to the degree of the expression of a given characteristic(s) of the qEEG phenotype. The expression of the characteristics of qEEG phenotypes in the middle range (green, Figure 5) is expected to correspond to optimal neurophysiological and mental functioning. Indeed, it has been shown that optimal characteristics of the qEEG phenotype are associated with optimal cognition, good personality structure, and overall well-being [506; 582; 677; 698; 699].