Social learning theory emphasises the importance of modelling others’ emotional reactions as a means of developing emotional patterns and responses. The behaviourists have developed a number of various classifications of behavioural theory, depending largely on the degree to which they refer to metaphysical or epistemological claims in their explanations of emotion. The two main categories of behaviour theory are psychological behaviourism and philosophical behaviourism. The psychological behaviourist approach to emotions can best be exemplified by the theories of James Watson and B. F. Skinner. Watson, in 1919, described emotion as ‘a hereditary pattern-reaction involving profound changes in bodily mechanisms as a whole, but particularly of the visceral and glandular systems’.

In Watson’s model of emotion, only three emotions can be distinguished: fear, rage, and love. He further states that these primary emotions can only by demonstrated in the newborn. Watson’s major contribution was his finding that emotional reactions could be learned through classic conditioning (Watson & Raynor 1920).

In 1967, Etzel and Gewirtz demonstrated that operant conditioning could have an impact on emotional development. Skinner refined Etzel and Gerwirtz’s work into a complex model where emotions evolve from an operant conditioning framework, where emotion is defined by the sets of operants and reinforcers that one optimises in any given setting (Skinner 1974). One of the major criticisms of Skinner’s theory is that some emotions exhibit little or no operant behaviour. For example, grief, especially when about a loss or death, does not result in any operant behaviour because no behaviour can bring about the desired results (Lyons 1992).

One of the most influential philosophical behaviourists was Gilbert Ryle. In 1949, his work The Concept of Mind outlined that emotion can be described in four different ways: inclination, moods, agitations, and feelings. Ryle viewed inclinations as the permanent disposition state of personality. Moods, agitations, and feelings were short-term displays overlying the main inclination theme. For example, if a person has the inclination to be kind, he may still experience short-term occurrences of irritability or cruelty, which would be attributed to his mood or feeling swings.

Further expansion of the social learning theory in recent years has been accomplished by Albert Bandura, who has added a cognitive component. According to Bandura, as a person’s representational ability improves, he/she can engage in emotional self-arousal by thinking about their own emotionally charged past experiences or even by recalling the experiences of others (Bandura 1986, 1989, 1991).

One of the main criticisms of social learning/behavioural theory is that it cannot explain the emergence of emotions that have not been acquired through modelling or conditioning, but seem to appear spontaneously.

The theory that emotions are nothing more than chemical reactions at synaptic connections has not been a popular theory among psychologists in the past. However, several recent findings and advancements in understanding of the neurochemical component of emotion have caused a wave of interest in the theories of biological emotion. Many neurochemical systems now appear necessary for the understanding and expression of emotions. Several areas of the brain have been implicated in the development, generation, and expression of emotions, particularly those regions known as the limbic system, which includes the hypothalamus, hypothalamus–pituitary axis, the anterior thalamus, the cingulated gyrus, the hippocampus, and amygdala (Rolls 1992; Halgren & LeDoux 1993). The importance of the amygdala in particular has emerged in its ability to determine the motivational significance of a stimulus (Gaffan et al. 1988), in the assignment of reward value to a stimuli (LeDoux 1990), and in the stimulation of behavioural and autonomic responses.

Instead of viewing emotions as central forces in the development of social interaction, cognitive psychologists view emotions as by-products of cognitive processes (Berk 1994). Several examples of cognitive theories follow, including Hebb’s discrepancy theory, Alder’s style of life theory, Epsteins cognitive-experiential self theory, and Apler’s reversal theory.

Donald Hebb (1947, 1949) explained in his discrepancy theory how distress reactions are elicited by novel stimuli. According to Hebb, when a person encounters a new stimulus, they compare it to a scheme or internal representation of a familiar object. The discrepancy between the stimulus and the internal representation determines the emotional response. Other researchers have modified Hebb’s theory, suggesting that a wide variety of emotional reactions could be explained by Hebb’s theory. For example, they argue that a positive emotion such as happiness could result from only moderate discrepancies between current stimuli and the internal scheme. Negative emotions, such as anxiety and fear, could result as the discrepancy between the present stimuli and the interval scheme widens (McCall & McGhee 1977; Kagan et al. 1978). This theory falls short when it is observed that people sometimes willingly seek out activities that are new and not in agreement with their internal scheme.

Alfred Adler, in his 1954 work Understanding Human Nature, was probably the first to integrate emotions, motivations, and cognition into one theory (Epstein 1993). According to Adler, individuals construct a belief system and a way of relating to the world which he termed a ‘style of life’. At the centre of a person’s style of life is a fictional goal which guides the individual in his attempts to overcome inferiority to gain social approval, a goal to which all humans strive. Emotions enter into Adler’s theory in two ways. Firstly, the quest for overcoming the feelings of inferiority provides an incentive for developing a style of life. Secondly, once the style of life has been developed, the emotions corresponding to that style of life are encouraged to develop. In other words, the style of life that one develops is a major determinant of the emotions that a person experiences, much like Aristotle’s ‘state of mind’ (Epstein 1993).

In the cognitive-experiential self theory (CEST), emotions are considered to be both influencing and being influenced by a person’s implicit theory of reality. The theory considers the primary emotions to be anger, sadness, joy, and affection. Cognitive affective units are constructed around the nuclei of the primary emotions. These cognitive units direct the development of critical adaptive behaviour patterns such as fighting, withdrawing, exploring, and showing affection. The development of these behavioural patterns results in emotionally rewarding experiences when they are consistent with a beneficial outcome to the individual (Epstein et al. 1992).

Apter’s reversal theory is explained in some detail here because it is one of the few theories that has a theoretical construct for encompassing changes over time in the individual which are clinically relevant for the functional neurologist. The centrepiece of reversal theory is a typology of distinct psychological states of mind. When people are in one of these states they want to experience a particular kind of emotion. The states are meta-motivational because they determine what types of experiences people want. In different states, people may react to the same stimuli in different ways, and experience distinctly different emotions. This theory focuses on how a person differs over time rather than on differences between people. Reversal theory suggests that there are eight different meta-motivational states, four pairs of opposite states. The reversal from one state to its opposite is the key feature of the theory. The two states of a pair are mutually exclusive and exhaustive; for example, a person is always in one state or the other, never both at the same time or neither state. The eight states of the reversal theory are serious–playful, compliant–defiant, power-oriented–affection-oriented, and self-oriented–other-oriented (Apter 1988). The first pair of meta-motivational states is composed of the telic and paratelic states. When in the telic state the person is primarily goal-oriented. Conversely, when a person is in the paratelic state they are best described as being playful. In this state the person does not attach much significance to what they are doing; they could not care less. The lability of a person, how readily they reverse back and forth between opposite states, varies at different times. The actual reversal process is dependent on one of three reasons: contingency, satiation, and frustration. Contingency is any change in the environment that instigates or necessitates a reversal. Satiation occurs when, in the absence of an environmental change, a reversal will eventually occur. Frustration–motivated reversals occur when a person remains in a particular state too long without achieving satisfaction (Frey 1997).

Reversal theory takes the approach of starting with motivation and experience and then interpreting the behaviour generated in light of these. Reversal theory emphasises that people are inconsistent and self-contradictory and goes so far as to say that healthy people are characterised by instability, not stability (Murgatroyd 1987).

Campos et al. (1994) define emotion as those processes which establish, maintain, change, or determine the relation between the person and the environment on matters of significance to the person. A person’s mood may be determined by a complex interplay of the emotions that they are experiencing at any one time as per the reversal theory. ‘Mood’ therefore can be defined as the way that we feel, while ‘affect’ can be defined as how we behave as a result of our mood. Neurologically, mood and affect depend on the complex interplay among diffuse networks of the frontal lobes and subcortical circuits. They can be influenced by genetic and environmental factors, similar to any form of activity in the nervous system. Long-term changes in mood and behaviour may occur because of ‘plastic’ changes in these networks. This refers to the moulding of nerve excitability and interconnectivity referred to as neural plasticity that occurs following repeated or essential exposure to an environmental stimulus, and subsequent alteration of gene expression in the associated nerves.

Other probably genetically determined neural systems seem primed to perform a variety of innate activities called ‘fundamental functions’ in the cortex. Fundamental functions comprise diffuse, overlapping, or parallel units that contribute to more complex interactions and multimodal processing in the nervous system. The more recent definition of fundamental functions applies to frontal-subcortical and limbic circuits, which are largely intact from birth. Executive/integrative functions apply to the prefrontal circuitry, which also comprise diffuse, overlapping, or parallel influences that contribute to more complex interactions and multimodal processing in the nervous system. Fundamental functions are generally less modularised than motor or sensory functions. In other words, they are less dependent on one single area within the brain, and instead receive their input from multiple sources and generate an output that can influence the entire state of the individual. These wide-ranging functionally connected areas are often receiving similar information at the same time and are often referred to as parallel distributed processing circuits. Dysfunction associated with these networks can therefore lead to so-called ‘circuit-related disorders’ affecting complex aspects of cognition or leading to mood and behavioural changes. Therefore, abnormalities associated with fundamental or executive regions of the brain may result in either ‘negative’ or ‘positive’ symptoms. Negative symptoms or deficits generally refer to decreased expression of a normal function, whereas positive symptoms refer to release of primitive functions or new behaviours. An example of a negative symptom is depression, where a patient may exhibit withdrawal from normal activities and social interaction and less expression in their face and body movements. An example of a positive symptom can be seen clinically in paranoid schizophrenia where environmental stimulus is amplified and taken out of context of reality. Positive symptoms may also be referred to as productive symptoms, release or escape phenomena. A classic example of ‘escape’ phenomena is the exaggerated autonomic reactivity that may be observed in patients with panic or anxiety disorders. Primitive areas of the brain and brainstem are allowed to summate or increase their firing more easily because of a loss of descending reticular inhibition from the more developed frontal areas of the brain. Obsessive–compulsive disorder (OCD) can also be viewed as an example of a release phenomena. The patient develops an irresistible urge to perform a specific action that will bring about relief of tension. While not purely seen as a ‘disinhibition’ syndrome, the patient often feels compelled to carry out an action that interferes with their daily lives. Cortical and subcortical areas implicated in mood and behavioural functions receive tonic influences from a large array of different neuronal circuits, some of which involve parallel distributed processing circuits that utilise a wide variety of neurotransmitters including dopamine, serotonin, noradrenalin, and acetylcholine. Thus the cumulative activity of these various circuits results in a temporal variation in the relative concentrations of the neurotransmitters utilised in each circuit.

The concept of parallel distributed processing is essential for healthcare practitioners to gain an understanding of the link between psychological and somatic or visceral health complaints. Not only may somatic health complaints affect the ability of an individual to exercise their normal daily routines, thus leading to altered mood and behaviour, but direct physiological connections exist that involve somatic and visceral afferents and the limbic system or ascending reticular activating systems of the brainstem and hypothalamus. One example of parallel distributed processes is outlined below, involving the rostral cingulate cortex as the limbic motor response area that responds to parallel afferent information also received by the sensory cortex. The rostral cingulate motor area (area 24) is responsible for primitive motor behaviours (fear, avoidance, etc.) mediated via the corticospinal and reticulospinal pathways. Activity in this region is also dependent on activation of the caudal cingulate motor area (area 25), which orientates the body in space. These cingulate motor areas and receptive regions of the cingulate and insular cortex that project to it are not only influenced presynaptically by subcortical and spinal neurons carrying sensory information, but they are also heavily modulated by monoaminergic neurons from the brainstem. The influence of dopamine, noradrenalin, and serotonin on sensory modulation, arousal, and orientation is complex in nature and discussed in further detail in Chapter 9.

Several classifications of depression have been developed. The following classification is based on the age or stage of development of the individual.

This disorder involves both manic and depressive episodes. Usually, bipolar disorders will appear in the manic phase followed by a normal period then a depressed phase, although many different patterns have been identified. In rare instances the mood may alternate between manic and depressive states with no periods of normal functioning; this is referred to as the cycling type of bipolar disorder. Another rare form of bipolar disorder involves the appearance of manic and depressive episodes simultaneously, which is referred to as a mixed type of bipolar disorder. For example, the person may show manic hyperactivity but weep and threaten suicide at the same time.

Bipolar disorder is much less common than major depression, occurring in about 0.4–1.2% of the population (Hirschfeld & Cross 1982). Bipolar disorder occurs in both sexes with equal frequency but in contrast to major depression is more prevalent in the upper classes (Bootzin & Acocella 1984). The premorbid history in bipolar disorder is usually normal with no warning symptoms and usually has its onset before age 30. The episodes of bipolar disorder are usually briefer and more frequent than major depression. Bipolar disorder is also more likely than major depression to have a familial connection.

Depression has been shown to be related to schizophrenia (Crow 1984), herpes simplex virus (Halonen et al. 1974), Ebstein–Barr virus (Amsterdam et al. 1986), human immunodeficiency virus (HIV) type I (Levy & Bredesen 1989), several autoimmune diseases (Johnstone & Whaley 1975), leukaemia (Greene 1954), and a variety of cancers (Persky et al. 1987). These relationships suggest disorders of the neuroimmune system in some fashion or other.

The role of neuroimmune function in depression has attracted attention for many years (Calabrese et al. 1987). Depressive illness poses a major public health problem with 2% to 3% of the population hospitalised or seriously afflicted at any one time; in this light, many investigators have approached depression from a neuroimmunological prospective (Stein et al. 1991). Many studies document that patients with depression show reduced immune function throughout a wide variety of immune function measures. Stein et al. (1985) found that in-patients with depression have poorer blastogenic responses than non-depressed controls. Depressed patients have also been shown to have a lower percentage of helper T-lymphocytes than non-depressed controls (Krueger et al. 1984). Irwin et al. (1990) showed that when compared to normal controls, men with major depressive disorder were associated with a 50% reduction in T-cell cytotoxicity. Not all research supports the above findings. Stein et al. (1991) reported in a comprehensive review that out of eight studies that they looked at only one found lymphopenia to be significant in depressive patients studied. Out of five additional studies examined by the same authors, again only one showed an alteration in neutrophil counts in depressed patients. Immune function studies in patients with depression have also been explored. Irwin et al. (1987b) found a decrease in cytotoxicity of natural killer cells in depressed patients as compared to controls. Other studies relating to natural killer cell cytotoxicity did not find any significant difference between controls and depressed patients (Mohl et al. 1987; Schleifer et al. 1989