High frequency oscillations measured with optically pumped magnetometers from the human retina

Measurement of human neural activity with optically pumped magnetometers (OPMs) is rapidly proliferating, with sensitivity approaching that of cryogenic sensors. Most neuroscience research with OPMs to date has investigated neural responses below 70 Hz, but higher frequencies are also of interest. However, sensitivity to higher frequencies may be limited by both the inherent operating bandwidth of the current generation of zero-field OPMs as well as by their generally lower amplitude. To assess the upper bounds of OPM sensitivity we used the stereotypical retinal response to flashes of light. Retinal responses to light flashes characteristically exhibit a neural response above 70 Hz called the oscillatory potential (OP) when recorded with electroretinography (ERG). Here we adopt the term retinal high frequency oscillation (rHFO) to include measurement of similar activity with OPMs. Our comparison of magnetoretinography (MRG) and ERG shows that rHFO can be measured up to 140 Hz using rubidium-based zero-field OPMs.