A neuroscientific perspective
THE PARADIGM OF CONSTRUCTED EMOTION
The brain's core function is to regulate energy so that homeostasis is maintained in the body. The active process by which the brain predicts and meets the energy needs of the organism before they manifest is called allostasis (Barrett, 2016; Jungilligens et al., 2022). Allostasis does not represent a state of the body, but rather a process of regulating energy according to costs and benefits. An efficient allostasis process, as mentioned above, anticipates the body's needs and meets them before they arise. While our brain thinks, perceives and feels, it also regulates and uses larger systems such as the autonomic nervous system, the immune system and the endocrine system to seek and provide a wider range of information.
This fact explains that the regions responsible for allostasis (anterior cingulate cortex, orbitofrontal cortex, insula, ventral striatum, medial prefrontal cortex and amygdala) simultaneously represent a pattern of brain activity that results in emotion. Thus, the aforementioned regions in the brain are multifunctional when it comes to the construction of mental categories (Barrett, 2016).
The brain models the external world in terms of the physiological needs of one's own body, which means that the brain's internal interoceptive model includes not only relevant statistical information about the regularities of the external world, but also about the regularities of the internal environment. The Active Inference Hypothesis, or otherwise known as the Predictive Coding Hypothesis, posits that simulations of the brain act as Bayesian filters for eastern sensory inputs, which prompt the construction of perceptions and other psychological phenomena. Simulations thus act as top-down predictive signals that continuously anticipate events in the sensory environment (Barrett, 2016; Jungilligens et al., 2022).
In order to properly manage the allostasis process, the system must rely on interoception: the brain's moment-to-moment monitoring of the body's internal physiological state.
To understand how the predictive processing model works, we first need to define what the brain is and how it works: the brain is a complex network of billions of communicating neurons, where many neurons can bind to one synapse, but a single neuron can also bind to several others (Barrett, 2016; Jungilligens et al., 2022). The aforementioned complexity of the brain allows for degeneracy, the ability for different regions of brain areas (activation patterns) to produce the same outcomes (Barrett, 2016).
The predictive processing that drives the allostasis process is rooted in the brain's cortical cytoarchitecture. The prediction pathway to the cortex travels from less laminated structures (a four-layered agranular tissue called the limbic cortex: ventral anterior insula, cingulate and posterior orbitofrontal/ventromedial prefrontal cortex; and primary motor cortex with small granular tissue) to higher laminated structures (six-layered areas; middle to posterior insula (primary interoceptive cortex) and areas of the coniocortex: primary somatosensory, auditory and visual areas).
Prediction errors thus start at the primary sensory cortex and go in the opposite direction: coniocortex - limbic brain, integrating at all levels. The most abstract multimodal features start in the default mode network. Prediction errors are updated according to their allostatic relevance (Jungilligens et al., 2022).
In the context of allostasis, the embodied concept (abstract mental representation) is thus a prediction. An AD HOC category is constructed when the prediction (i.e. the embodied concept) matches the incoming sensory information and the prediction error is consequently reduced. In other words, features of the past are put together in such a way as to give meaning to the present. The brain thus categorises the incoming sensory information, gives it an emotional meaning and creates an experience according to the example categories of these emotions. The categories are unique, situation-specific and semi-specific.
Do FND patients have poor chronic energy management?
One theory postulates that FND patients have chronic allostatic energy management problems, meaning that allostasis is characterised by suboptimal emotion construction. Less granular and effective concepts (e.g., "tiredness" and "feeling bad") crowd out more accurate (predictive) concepts, perpetuating chronic ineffectiveness. Also, 94% of patients report a symptom of chronic fatigue.
FND can occur in the context of a deviant construction of emotions.
The second theory refers to a deficit in the repertoire of available emotion concepts and/or a failure to generate conceptual categories for emotions. Thus, patients with FND are thought to have an increased pervasive tendency to categorise incoming afferent sensory information as body- and/or health-focused concepts rather than emotion-focused concepts.
Modified learning/updating of model errors
The inefficient use of allostatic and/or interoceptive models is thought to be due to problems in the accuracy of the signals originating from the salience network. Deficits are found in the following areas:
sensory processing,
interoceptive precision,
biased attention,
motor learning disabilities, and
difficulties in constructing a conceptual category for emotions.
Alexithymia, panic attacks without panic and dissociation can be reversed.
The cause of alexithymia, based on emotion construction theory, is the limited availability of granular emotion concepts, leading to inefficient adaptive contextualisation of sensory input. Non-panic panic attacks, on the other hand, are accompanied by autonomic symptoms that resemble those of a panic attack but lack the associated subjective perception. Finally, dissociation is a dimensional construct involving depersonalisation and derealisation, and refers to affect not fitting the constructed experience.
Constructing emotions in FND patients
Patients with FND often do not experience high arousal and perhaps negative (valence) affect as an example of emotion, but rather the construct is categorised as either body, health or illness.
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Barrett, L. F. (2017). Categories and their role in the science of emotion. Psychological inquiry, 28(1), 20-26.
Jungilligens, J., Paredes-Echeverri, S., Popkirov, S., Barrett, L. F., and Perez, D. L. (2022). A new science of emotion: implications for functional neurological disorder. Brain, 145(8), 2648-2663.