Embodied Technologies for Mental Health: Leveraging Synthetic Emotions for Dissociation and Anhedonia

Two streams of information reach the brain at every moment. The first comes from the outside world through the classical senses, such as sight, hearing, and touch on the skin; this is called exteroception. The second comes from inside the body: the contraction of the heart sensed by baroreceptors; the expansion of the lungs sensed by pulmonary stretch receptors; temperature, sensed by thermoreceptors; and muscle tension detected by muscle spindles. The perception of these internal signals is called interoception. The brain actively and continuously predicts what it is about to sense, compares the prediction with what arrives, and uses the difference to correct the next prediction and ultimately control the whole system.^1,2

It follows that interoception and exteroception cannot be separated when we speak about feeling. The same racing heart can be read as fear in a dark alley, excitement on a first date, or exertion on a staircase. The bodily signal is the same; the resulting emotional experiences differ in profound ways and drive decision and behavior. Stanley Schachter and Jerome Singer found that individuals given an injection of adrenaline reported different emotions depending only on the social situation they were placed in.³ Stuart Valins then showed that the bodily signal need not even be real. When men were given false feedback that their heart had sped up at a particular photograph, they came to prefer that photograph.⁴ This is known as misattribution of arousal. If we can control the bodily signal and the context together, we can direct the resulting emotion.⁵

When bodily signals are read with too much confidence, a normal rise in heart rate can be taken as the onset of a heart attack and trigger a panic attack. When they are read with too little confidence, the world feels flat and unreal. Across anxiety, depression, eating, and trauma disorders, the same patterns emerge of a miscalibrated reading of the body's signals, rather than any issue with the signals themselves.⁶ In a recent review for Neuroscience and Biobehavioral Reviews, we identified 3 points of intervention for psychiatry research: brain processes, bodily signals, and the surrounding environment (contextual cues). Tools that act on these points fall into 3 families: those that measure bodily signals, those that modulate them, and those that do both at once in a closed loop, timing a bodily sensation to the person's state.⁸

For example, Laura Barca and Giovanni Pezzulo have applied this idea to anorexia nervosa, where food restriction can be understood, in part, as an attempt to keep an uncertain interoceptive stream under control.⁷ Related approaches deliver controlled sensations through sound or affective touch; in Milan, Italy, Daniele Di Lernia and Giuseppe Riva have built sound-based systems that modulate interoceptive signals.⁹ In this brief article, I review 2 more interventions that sit at the closed-loop end of this range. Both are noninvasive, drug-free, and meant to stand beside existing treatment as opposed to replacing it. They address 2 of the hardest symptoms to treat in psychiatry: dissociation and anhedonia.

Dissociation

The first application concerns dissociation, an altered state of consciousness in which a person's own actions, or the world around them, feel unreal and not their own. Yochai Ataria and Adam Linson have framed dissociation, and trauma more generally, in terms of agency: the ordinary, prereflective sense that I am the author of my own movements, that when I reach for a cup, it was I who moved.^12,13 On this account, the traumatic event overwhelms the sense of agency, because the person could not act to protect themselves, and the resulting helplessness leaves a lasting friction between perception, intention, and action. Many later symptoms of posttraumatic stress disorder, including dissociation, avoidance, and hypervigilance, can be read as consequences of the catastrophic loss of agency and as an attempt to repair it.¹⁴

If trauma disrupts the link between action and sensation, a tool that strengthens that link may help repair it. This is the principle behind BeSound, which we developed and tested with Vladimir Adrien, Marion Trousselard, and colleagues in Paris, France (www.besound.io).¹⁴ Sensors worn on the body convert the patient's movements into sound in real time, so that every gesture immediately produces a coherent sound under the patient's own control (for example, a punch leads to a punching sound). In an exploratory study in healthy participants, this gesture sonification increased bodily awareness, the sense of control, immersion, and pleasure. Interestingly, the effect was a function of experience, where novices benefited more from it than trained dancers.¹⁵ Unlike virtual reality, sonification places the body and the surrounding world at the center and, most importantly, keeps the patient in contact with the clinician, preserving and strengthening the therapeutic alliance. The system is currently under investigation in the clinical trial SONICUMP at the Greater Paris University Hospitals for acute stress response in an emergency setting.

Anhedonia

The second application concerns anhedonia: the loss of the capacity to feel pleasure and the motivation to pursue it. Anhedonia affects roughly 70% of patients with major depressive disorder and is a hallmark of treatment resistance and relapse. It responds poorly to the serotonergic antidepressants that remain first-line treatments, which sometimes blunt it further. Anhedonia also predicts worse outcomes, and, in older patients, a persistent loss of drive is often an early sign of neurodegeneration.

We hypothesized that anhedonia could be addressed through an emotion with a distinct bodily signature: the aesthetic chill, a powerful emotion marked by shivers down the spine and goosebumps on the arms. Aesthetic chills are marked by anomalous sensations ordinarily tied to temperature regulation (shivers, goosebumps). With Abhinandan Jain at MIT Media Lab and Diego Pizzagalli's group and Kim Willment at Harvard Medical School, we reasoned that the chill could serve as a lifeline in depression because of its neurobiology: It engages the very reward circuitry disrupted in anhedonia, the dopaminergic projection from the ventral tegmental area to the nucleus accumbens and on to the orbitofrontal cortex, which encodes expected reward from the environment and enables its future retrieval. This extends pioneering work by Robert Zatorre and Anne Blood, who showed that chills activate this circuit, and by Valorie Salimpoor, who characterized the phasic dopamine release during the experience.¹⁶

Chills are elicited by audiovisual stimuli, which we validated through extensive testing and machine learning and made openly available to researchers (www.chillstv.com). These stimuli work through meaning-making: a moment in music or film that the person finds significant. Crucially, that meaning enters consciousness through the body and produces a concrete physical event, the shivers or goosebumps, with measurable changes in heart rate and skin response. The chill is therefore a clear instance of the principle above: a meaningful situation, an internal bodily signal, and the brain's reading of the 2 combine into 1 felt emotion that can be produced on demand.

Because the bodily sensation is part of this loop, strengthening it strengthens the whole emotion. With Adam Haar Horowitz, Jain, and Pattie Maes, we built a wearable device, worn along the spine, that delivers precisely timed cold in synchrony with the stimulus. Amplifying the bodily signal this way increases the downstream effects on mind and brain alike: Felt pleasure grows, prosocial feeling grows, and reward-related processing increases with them.¹⁷ Acting on the body, in other words, changes the mental and neural state that follows from it, a closed-loop, designed emotion in the most literal sense.

Using the Probabilistic Reward Task, the standard behavioral measure of reward responsiveness, we found that among people with elevated depressive symptoms, those with high anhedonia who felt chills showed a measurable improvement in reward learning, whereas those who did not showed none.¹⁸ In a separate study, chills shifted the harsh, self-critical beliefs that sustain depression, around shame and self-acceptance, in the direction reported after psychedelic-assisted therapy, but without any drug.¹⁹ A patient who feels no pleasure in ordinary life can still obtain a measured dose from 3 minutes of carefully chosen video, enough to produce a real reward response and re-engage the reward circuit toward healthy behavior. We are now developing ReWire, a software-based tool to safely and reliably induce chills for patients and restore reward in exactly this way (www.rewire.bio). Because the effect is grounded in reward neurobiology, it can meaningfully be combined with neuromodulation, medication, and psychotherapy.

Concluding Thoughts

The value of this kind of technology is a route of intervention that carries little risk and uses no needles, implants, or drugs. Body-based intervention is not new to psychiatry: interoceptive exposure, in which a patient is helped to confront feared bodily sensations in a controlled way (for example, breathing through a thin straw to reproduce breathlessness), is already established in the treatment of panic and anxiety, as Hannah Boettcher, Alex Brake, and David Barlow have described.²⁰ What is new is the ability to deliver the right sensation, at the right time, in the right context, to the right person, and the possibility to engineer novel emotional states so patients can access them safely and robustly in the course of treatment.

Dr Schoeller is the cofounder and CEO of ReWire Neurotechnologies and a senior research scientist at the Institute for Advanced Consciousness Studies in Santa Monica, California. His work spans affective neuroscience, human–technology interaction, and psychiatric applications. He previously held research positions at the MIT Media Lab and the Gonda Multidisciplinary Brain Research Center. He holds equity in and has received compensation from both companies. The views expressed are his own.

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