We Induced Smells With Ultrasound

The post says focused ultrasound was used to stimulate scent-processing regions in the brain and reliably produce distinct smells, including fresh air, garbage, ozone, and burning wood. It describes the setup, the forehead-based targeting approach, the safety checks, and the blind trial used to validate the effects.

The author also argues that the olfactory system could be useful as a non-invasive channel for writing information into the brain, because it has many receptor types and close links to core brain regions. The post frames the work as an early step toward learning to associate stimulation patterns with meanings.

Reading notes

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• Focused ultrasound was aimed at the olfactory bulb through the forehead to produce smell sensations.
• The team says this kind of olfactory stimulation had not been done before, even in animals.
• They report four effects: fresh air, garbage, ozone-like sensation, and burning wood.
• The setup changed from a handheld probe to an improvised headset for more stable positioning.
• MRI was used to estimate where the ultrasound focus would land relative to the olfactory bulb.
• The described ultrasound preset used 300 kHz, about 39 mm focal depth, 50–55° steering, and 5-cycle pulses at 1200 Hz.
• Safety checks included measuring pressure in a water tank and staying within limits for mechanical index and thermal dose.
• They also tried to avoid the optic nerves by limiting asymmetry and steering angle.
• The authors distinguish between smells and weaker sensations that feel more diffuse and slower to appear.
• They used an auditory mask and a trial design to reduce placebo effects and test discrimination.
• They suggest the olfactory system could support a high-dimensional channel for writing information into the brain.
• The post connects this idea to the 400 receptor types in the nose and to possible links with memory and emotion.