From Bioimpedance to Light: Reflections on the 2026 Nobel Prize in Physiology or Medicine
The 2026 Nobel Prize in Physiology or Medicine, awarded to Peter Hegemann, Georg Nagel, and Karl Deisseroth for discoveries concerning light-gated ion channels and optogenetics, brought me back to a research problem I worked on about 20 years ago. Our work was part of a broader effort to detect neural activity through changes in bioimpedance using electrical impedance tomography (EIT). The award reminded me that the opening of an ion channel can be approached both as something to measure and as something to control. Around 25 years ago, a clinical neurophysiologist at University College London explained the physical basis of this approach to me. When a neuron becomes active, ion channels open and its membrane conductance changes. The hope was that the resulting change in tissue impedance would allow researchers to follow the propagation of an action potential. A central challenge was obtaining reliable measurements of small, brief changes within signals influenced by many cells, extrac...