This new tool could tell us how consciousness works

Transcranial focused ultrasound, a noninvasive brain imaging tool depicted in the illustration, may help researchers gain knowledge about human consciousness. Image: MIT News; figure courtesy of the researchers

Consciousness is famously a “hard problem” of science: We don’t precisely know how the physical matter in our brains translates into thoughts, sensations, and feelings. But an emerging research tool called transcranial focused ultrasound may enable researchers to learn more about the phenomenon.

The technology has entered use in recent years, but it isn’t yet fully integrated into research. Now, two MIT researchers are planning experiments with it, and have published a new paper they term a “roadmap” for using the tool to study consciousness.

“Transcranial focused ultrasound will let you stimulate different parts of the brain in healthy subjects, in ways you just couldn’t before,” says Daniel Freeman, an MIT Lincoln Laboratory researcher and co-author of a new paper on the subject. “This is a tool that’s not just useful for medicine or even basic science, but could also help address the hard problem of consciousness. It can probe where in the brain are the neural circuits that generate a sense of pain, a sense of vision, or even something as complex as human thought.”

Transcranial focused ultrasound is noninvasive and reaches deeper into the brain, with greater resolution, than other forms of brain stimulation, such as transcranial magnetic or electrical stimulation.

“There are very few reliable ways of manipulating brain activity that are safe but also work,” says Matthias Michel, an MIT philosopher who studies consciousness and co-authored the new work.

The paper, “Transcranial focused ultrasound for identifying the neural substrate of conscious perception,” is published in Neuroscience and Biobehavioral Reviews. The authors are Freeman, a technical staff member at MIT Lincoln Laboratory; Brian Odegaard, an assistant professor of psychology at the University of Florida; Seung-Schik Yoo, an associate professor of radiology at Brigham and Women’s Hospital and Harvard Medical School; and Michel, an associate professor in MIT’s Department of Philosophy and Linguistics.