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Sniffing enables communication and environmental control for the severely disabled

Abstract
Paradoxically, improvements in emergency medicine have increased survival albeit with severe disability ranging from quadriplegia to “locked-in syndrome.” Locked-in syndrome is characterized by intact cognition yet complete paralysis, and hence these individuals are “locked-in” their own body, at best able to communicate using eye blinks alone. Sniffing is a precise sensory-motor acquisition entailing changes in nasal pressure. The fine control of sniffing depends on positioning the soft palate, which is innervated by multiple cranial nerves. This innervation pattern led us to hypothesize that sniffing may remain conserved following severe injury. To test this, we developed a device that measures nasal pressure and converts it into electrical signals. The device enabled sniffs to control an actuator with speed similar to that of a hand using a mouse or joystick. Functional magnetic resonance imaging of device usage revealed a widely distributed neural network, allowing for increased conservation following injury. Also, device usage shared neural substrates with language production, rendering sniffs a promising bypass mode of communication. Indeed, sniffing allowed completely paralyzed locked-in participants to write text and quadriplegic participants to write text and drive an electric wheelchair. We conclude that redirection of sniff motor programs toward alternative functions allows sniffing to provide a control interface that is fast, accurate, robust, and highly conserved following severe injury.
Footnotes
- 2To whom correspondence should be addressed. Email: noam.sobel{at}weizmann.ac.il.
Author contributions: A.P., L.S., A.W., R.K., L.H., Y.Y., N. Soroker, and N. Sobel designed research; A.P., L.S., A.W., R.K., L.H., Y.Y., N. Soroker, and N. Sobel performed research; A.P., L.S., R.K., L.H., Y.Y., N. Soroker, and N. Sobel analyzed data; and A.P., L.S., N. Soroker, and N. Sobel wrote the paper.
Conflict of interest statement: The Weizmann Institute has filed for a patent on the sniff-controlled technology that is at the heart of this manuscript.
↵*This Direct Submission article had a prearranged editor.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1006746107/-/DCSupplemental.
Freely available online through the PNAS open access option.