Consciousness: cure it, recover it, understand it. The ultrasound bet

They can pass through the skull, reach deep structures such as the thalamus or the amygdala with millimetre precision, and influence the activity of a small part of the brain for a few seconds. They are called transcranial ultrasound, very high-frequency sound waves applied from the outside that exert slight mechanical pressure on neurons, temporarily modifying their activity, without damaging them. The result is a reversible and controlled modulation of specific brain circuits, without surgery or implants. This technology is opening up new perspectives, from the treatment of depression to disorders of consciousness and chronic pain. And now also in research into the origins of consciousness, understood as lived experience: seeing a colour, feeling pain, perceiving oneself as present. Is it neurological activity that gives rise to conscious experience?

So far, on this front, research has been able to explain the mechanisms linking biological activity in the brain to consciousness, but not whether that area of the brain is indispensable for generating it. "It's one thing to say that those neurons responded electrically, it's another to say that the person saw the light," clarifies Daniel Freeman, an engineer at the Massachusetts Institute of Technology (MIT). Freeman is part of a project that has brought together engineers, like himself, neuroscientists, radiologists and even philosophers, from MIT and Harvard University, to try to answer this question, using neuromodulation with ultrasound. The idea is that if modulating a specific area of the brain changes whether and how the subject sees, hears, or reports feeling something, then it is possible to test the causal role of that circuit in conscious experience. The group started with two experiences: sight and pain. In the case of vision, the researchers propose to work on stimuli at the limit of the perceptual threshold: images so faint that they are sometimes seen, sometimes not. By modulating a specific area of the brain with ultrasound, for example a region of the visual cortex or a frontal area involved in the integration of information, one can test whether it changes the fact that the subject reports seeing something. Pain offers another test. By stimulating deep structures such as the thalamus, which coordinates a lot of sensory information, the American researchers want to understand where the conscious component of pain is formed, that which is not just an automatic response, but a lived experience.

In the paper published last January in Neuroscience, the group outlines a roadmap, a method for experimental testing, indicating which questions to ask, how to choose targets in the brain, how to combine stimulation and behavioural measures, and how to compare the results with leading theories of consciousness. Another front of scientific research investigates disorders of consciousness, where vigilance or the ability to have experience is impaired, such as coma, vegetative state and minimally conscious state. In a review published in 2025 in Critical Care, a group of researchers analysed available clinical studies to see whether targeted stimulation of deep structures with ultrasound could promote even partial recovery of consciousness. Some of the patients who underwent stimulation with ultrasound (at low intensity) showed signs of improvement in their response to stimuli and, in a small group, a shift towards a higher state of consciousness was seen, as if from a vegetative state to a minimally conscious state. The resonance images suggested a reactivation of the circuits involved in vigilance. But the data remain preliminary and the phenomenon seen must be confirmed with further studies.

Scientists are also experimenting with ultrasound in cases of altered content and quality of conscious experience, such as depression, which according to the World Health Organisation affects more than 280 million people worldwide. A review published in Brain Sciences in 2025 collected different studies on whether low-intensity ultrasound could modulate mood-regulating circuits. In animals, improvements in depression-related behaviour were observed; in healthy volunteers, temporary changes in brain networks involved in emotional regulation; and in patients with drug-resistant depression, reductions in symptoms in some of the treated cases. A controlled clinical trial published in 2024 in Psychiatry Investigation also showed that a few sessions of targeted stimulation with ultrasound can reduce depressive symptoms, without any major adverse events. Meanwhile, the Consciuness Club was born at MIT in Boston: in addition to the relationship between the brain and consciousness, unconscious perception, consciousness in animals and artificial intelligence systems are being investigated. We are only at the beginning of a dialogue with the brain that may hold many answers for us, even unexpected ones