Early findings suggest stimulating multiple brain regions could enrich artificial touch

Researchers at the University of Osaka discovered that stimulating two areas of the brain together can lead to more complex artificial touch sensations. The study, published in Brain Stimulation, tested whether stimulating the primary somatosensory cortex (S1) and the insular cortex simultaneously could create sensations beyond what is typically produced by stimulating S1 alone.

Touch perception involves information about location, texture, pressure, and temperature. The insular cortex is responsible for processing temperature, pressure, pain, and internal bodily states.

The study involved three epilepsy patients with intracranial electrodes implanted for monitoring. The researchers stimulated S1 alone, the insula alone, and both regions simultaneously using 50-Hz electrical stimulation. When the regions were stimulated together, patients reported richer, more multifaceted touch sensations. One patient described a gentle hand on their face, another experienced a choking sensation in their fingers, and the third felt numbness combined with painless warmth. These sensations were not simply additive effects of stimulating each region individually.

The study had limitations, including using only three patients, not including a sham stimulation condition, relying on subjective verbal reports, not systematically matching stimulation intensity, and testing conditions only once. Due to these limitations, the findings cannot definitively attribute the effects to simultaneous activation alone.

However, the results suggest that multisite stimulation may influence how touch components are combined, which could be useful for developing sensory neuroprostheses that communicate more aspects of touch perception. Further research in larger, controlled studies is needed to confirm these findings. Lead author Dr. Takamitsu Iwata noted that this approach could help reveal how brain networks create unified sensations.