The brain is a predictive machine, and when its emotional calculations go awry, the body can speak a language of symptoms that medicine is only now learning to understand.
Imagine your body suddenly betraying you. One day, you wake up with an arm that hangs limp, unable to follow your commands. Or perhaps you begin experiencing seizures that resemble epilepsy but leave doctors baffled as brain scans show no neurological damage. These are the everyday realities for people living with Functional Neurological Disorder (FND), a condition at the intersection of neurology and psychiatry that has mystified physicians for centuries.
FND reflects genuine impairments in brain networks leading to distressing motor, sensory, and cognitive symptoms—weakness, tremors, seizures, or paralysis—despite the absence of structural damage to the nervous system 1 4 .
For decades, the medical establishment has struggled to understand how emotions contribute to FND, trapped by outdated notions of how emotions work. But a revolutionary science of emotion is now emerging, offering not just explanations but real hope.
For generations, the classical view of emotion dominated science and medicine. This perspective suggested we're born with hardwired emotion circuits—a fear circuit that activates when we see a snake, an anger circuit that fires when we're threatened.
However, accumulating cognitive-affective neuroscience evidence from almost every domain of measurement is strongly inconsistent with this classical view 4 . Research revealed that the same emotion category, like fear, doesn't consistently produce the same physiological changes, facial expressions, or brain activity patterns across different situations or people 4 7 .
Enter the theory of constructed emotion, pioneered by psychologist Lisa Feldman Barrett and colleagues. This groundbreaking framework suggests our brains don't detect emotions but construct them in the moment, much like a chef improvising a meal from available ingredients 4 .
According to this theory, the brain's fundamental mission is allostasis—efficiently forecasting and meeting the body's energy needs before they arise 4 . To accomplish this, the brain constantly generates predictions based on past experiences, comparing incoming sensory data from the body and the world against these expectations. When the brain categorizes this sensory information using emotion concepts from your culture, you experience an instance of emotion—what we might call "fear," "sadness," or "joy" 4 .
| Aspect | Classical View | Constructed View |
|---|---|---|
| Origin | Biologically hardwired circuits | Constructed in the moment by the brain |
| Function | Reaction to stimuli | Predictive regulation of energy needs |
| Consistency | Universal expressions and patterns | High variability across contexts and individuals |
| Brain Process | Detecting and responding to emotions | Predicting, categorizing, and constructing emotions |
How do scientists study something as fleeting and subjective as emotion? A clever Stanford Medicine study published in May 2025 provided unprecedented insight into how fleeting sensory experiences transform into lasting emotional states—in both humans and mice 3 .
The research team, led by Dr. Karl Deisseroth, devised an elegant experiment using a mildly unpleasant but safe stimulus: precisely timed puffs of air to the eye, similar to what you might experience during an eye exam. This approach allowed them to study emotional responses without causing harm while maintaining precise control over timing, duration, and intensity 3 .
The human participants were patients who already had electrodes implanted in their brains for epilepsy monitoring. This rare access to direct brain recordings allowed researchers to track neural activity with extraordinary precision while subjects received the eye puffs 3 .
Mild, safe air puffs to the eye used to study emotional responses
Strong, widespread spike alerting the brain to new sensory information
Longer-lasting activity in emotion circuits establishing emotional state
The researchers observed a distinctive two-phase pattern in brain activity. Immediately after each eye puff, a brief but strong spike of activity broadcast "news" of the sensation throughout the brain. This was followed by a separate, longer-lasting phase of brain activity more specifically localized to circuits associated with emotion 3 .
When researchers delivered a series of eight rapid-fire eye puffs, they observed something remarkable: the second-phase brain activity accumulated, putting both humans and mice into a generalized negative emotional state. In mice, this was further evidenced by their persistently reduced willingness to engage in reward-seeking behavior—a classic hallmark of an enduring emotional state 3 .
The most compelling evidence came when researchers administered ketamine, a medication known to cause temporary dissociation at lower doses. Under ketamine's influence, patients described the air puffs differently—as "entertaining" or like "little whispers on my eyeballs"—and notably didn't show the same self-protective behaviors 3 . The drug had specifically targeted the emotional response, not the sensory experience itself.
Studying emotions in the lab requires both ingenuity and sophisticated technology. Researchers in this field employ a diverse arsenal of tools to measure how the brain constructs emotional experiences.
Electrodes implanted deep in the brain provide millisecond-by-millisecond tracking of neural activity across multiple regions simultaneously. This offers unprecedented resolution for capturing how brain networks communicate during emotion construction 3 .
Tools like skin conductance response, heart rate monitoring, and cortisol measurement track the body's physiological responses during emotional experiences. These reveal how the brain's predictions manifest physically 8 .
This technology measures brain activity by detecting changes in blood flow, allowing researchers to identify which brain networks activate during different tasks or emotional states 4 .
By monitoring where and how long people look at emotional stimuli (like threatening faces), researchers can detect automatic attentional biases that operate outside conscious awareness 8 .
| Network | Key Regions | Role in Emotion and FND |
|---|---|---|
| Salience Network | Anterior insula, anterior cingulate | Detects relevant stimuli; often shows altered activity in FND |
| Default Mode Network | Medial prefrontal, posterior cingulate, parietal | Active during self-referential thought; may contribute to anomalous experiences in FND |
| Limbic Regions | Amygdala, hippocampus | Involved in emotional processing and memory; shows heightened reactivity in some FND patients |
| Sensorimotor Networks | Motor cortex, somatosensory regions | Execute movement and process bodily sensations; disrupted in FND symptoms |
The theory of constructed emotion doesn't just revolutionize our understanding of feelings—it provides a powerful new framework for treating Functional Neurological Disorder. If FND symptoms emerge from glitches in how the brain constructs emotion categories and predicts energy needs, treatment should focus on recalibrating this predictive process 4 .
Difficulty identifying and describing one's emotions affects many with FND. Through the constructionist lens, this isn't a character flaw but reflects a less detailed conceptual system for emotions 4 .
Feeling detached from one's thoughts, feelings, or body can be understood as the brain's attempt to deal with overwhelming prediction errors by shutting down incoming sensory data 4 .
Patients experience physical symptoms of panic (racing heart, sweating) without the feeling of panic—illustrating how the brain can generate physical responses without constructing the conscious experience .
Help patients build more nuanced categories for their internal experiences 4 . This involves learning to differentiate between similar emotional states and developing a richer emotional lexicon.
Practice recognizing subtle bodily sensations and reattributing physical symptoms to emotional causes when appropriate . This helps patients understand the connection between physical symptoms and emotional states.
Develop skills for detecting, regulating, and fulfilling the body's energy needs before they become overwhelming . This proactive approach helps prevent the buildup of prediction errors that can lead to FND symptoms.
Both bottom-up approaches (like sensorimotor psychotherapy that works with bodily sensations) and top-down approaches (like cognitive behavioral therapy that works with thoughts and beliefs) can have complementary benefits in this recalibration process .
The new science of emotion represents more than just a theoretical shift—it offers a profound integration of our understanding of brain, mind, and body.
By recognizing emotions as constructed categories that help the brain regulate the body's energy needs, we can finally move beyond unproductive debates about whether FND symptoms are "real" or "all in the head."
The implications extend far beyond FND, touching everything from how we understand mental illness to how we raise and educate children to develop robust emotional conceptual systems.
As this research continues to unfold, we're learning that the path to healing mysterious conditions may require listening to what the body is trying to say—not in the language of disease, but in the complex, constructed vocabulary of human emotion.
When those predictions go awry, the body speaks its mind in symptoms we're only now learning to understand. The revolutionary insight that we construct our emotional worlds offers not just explanation, but empowerment—the recognition that with new understanding, we can learn to construct them differently.