Review: A New Science of Emotion and Its Implications for Functional Neurological Disorder
Key findings
- Researchers at Massachusetts General Hospital recently reviewed principles of brain function that are relevant to functional neurological disorder (FND) and related brain-mind-body conditions, proposing new links to the theory of constructed emotion
- Drawing on that theory, the authors then described ways in which altered emotion category construction can be understood as an integral component of FND pathophysiology and related functional somatic symptoms
- An important therapeutic strategy for patients with FND may be to guide them to re-attribute physical symptoms to newly developed or more refined emotion categories
An ongoing debate in neurology and psychiatry is the extent to which emotions have a mechanistic or etiological role in functional neurological disorder (FND). Strikingly, the discussion has largely disregarded the question of what emotions are in the first place.
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The classical view is that specific emotions, such as fear, can be reliably identified by certain physiological features and/or behavioral patterns. Yet across studies, and even across subjects within the same study, there's substantial variability in how emotions match up with facial movements, vocalizations, patterns of autonomic nervous system physiology, brain activity profiles and single-neuron recordings.
In Brain, two affiliated faculty members with the Athinoula A. Martinos Center for Biomedical Imaging at Massachusetts General Hospital—David L. Perez, MD, MMSc, also director of the Functional Neurological Disorder Unit and Research Program in the Departments of Neurology and Psychiatry, and Lisa Feldman Barrett, PhD, also affiliated with the Psychiatric Neuroimaging Division of the Department of Psychiatry—and colleagues present a new science of emotion and its implications for the pathophysiology of FND. Co-first authors of this article were Drs. Johannes Jungilligens and Sara Paredes-Echeverri, two talented post-doctoral research fellows in the FND Research Group.
Allostasis and the Predictive Brain
The central nervous system forecasts the energy needs of the body, and tries to meet them, through a process known as allostasis. The brain models the body in the world and also interprets physiological signals made available by interoception, the moment-to-moment modeling of the body's internal state.
The brain compares incoming sensory information from the body and the world to features that have already been classified, giving meaning to the current input. In essence, the brain derives meaning from past events (and concepts) that seem similar to one's current experience.
Abstract mental representations and the visceromotor and motor action plans used to deal with the sensory signals in the past are applied to the current sensory information. The individual thus uses an "embodied concept" as a prediction.
If the prediction proves to match the incoming sensory information and prediction error is minimized, an ad hoc mental "category" is constructed. Newly constructed categories help the brain sort, understand and deal with incoming sensory data.
The Theory of Constructed Emotion
An experience of emotion can be a reference for a constructed category. Conceptual categories of emotion categorize physical signals, give them emotional meaning and make the experience an instance of that emotion category.
Life experiences inform the development and refinement of one's repertoire of emotion concepts. Individuals who lack a supportive and stable environment during development may not learn to discern important from unimportant signals for allostasis. Therefore, the task of creating and refitting emotion categories might be performed less efficiently and distinctly across instances.
In this way, the efficiency of the brain's predictive process can be disrupted, and the construction of an emotion category may not be well tailored to the immediate environment.
Reconceptualizing FND Using the Theory of Constructed Emotion
The authors propose that functional neurological and somatic symptoms can be caused by disruptions of the predictive processing that's part of emotion category construction. They present six interrelated proposals, which are not intended to apply to all individuals with FND:
There is chronic allostatic energy mismanagement in FND related to suboptimal emotion construction—For example, the concept of "chronic fatigue" may gradually supplant a more efficient emotion category construction. Hyperarousal and hypervigilance, two other common symptoms of FND, also relate to energy mismanagement.
FND can occur in the context of aberrant emotion construction—Some individuals may have outright impairments in constructing an emotion category for a particular instance. For example, for individuals with high arousal states associated with physical symptoms, such as paroxysmal motor phenomena, perceptual inferences may make sense of them by constructing an emotion category such as "fear" or "being shocked." Others in the same instance may fail to construct an instance of an emotion category, instead predicting (and matching with) a non-emotion concept such as "shaking."
Prediction error learning is altered in FND—Some people with FND show deficits in sensory processing, deficits in interoceptive accuracy, biased attention and impairments in motor learning.
Three common FND symptoms can be understood as manifestations of aberrant emotion construction:
- Alexithymia (defined in part as difficulties in identifying/describing feelings)
- "Panic attack without panic" (individuals endorse the autonomic symptoms of panic attacks but not the emotion of panic itself)
- Dissociation
The theory of constructed emotion helps contextualize the debate on emotion in FND—Individual differences in emotion construction help explain why a clinician might evaluate someone with FND as "anxious." For example, while the individual denies the presence of that emotion. A key implication of the theory of constructed emotion is that humans cannot know someone else's subjective emotional experience.
Adverse life experiences may negatively affect an individual's repertoire of conceptual categories for emotions and their refinement—Not all people with FND report early-life adversity or antecedent trauma, but multiple cohort studies have identified associations between the magnitude of adverse experiences and the severity of functional neurological symptoms. The authors speculate that aberrant emotion construction and related factors contributing to inefficient allostatic modeling (e.g., insecure attachment) may mediate this correlation.
Therapeutic Implications
An important therapeutic strategy for patients with FND may be to guide them to re-attribute physical symptoms to newly developed or more refined emotion categories that aid more efficient performance of allostasis. This suggestion contrasts with psychodynamic theories that an emotion concept has been formed but is repressed or "converted."
Therapies focused on teaching patients to detect, regulate and fulfill the body's needs (that is, perform "allostatic maintenance") deserve research in FND. Bottom-up (e.g., sensorimotor psychotherapy) and top-down (e.g., cognitive behavioral therapy) approaches may have complementary benefits.
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