Optical coherence tomography for cross-sectional imaging of neural activity

We report a functional optical coherence tomography cross-sectional scanner to detect neural activity using unmyelinated nerves dissected from squid. The nerves, unstained or stained with a voltage-sensitive dye, were imaged in a nerve chamber. Transient phase changes from backscattered light were detected during action potential propagation. The results show that the scanner can provide high spatiotemporal resolution crosssectional images of neural activity (15 μs/A-line; 0.25 ms/B-scan; ∼8.5 × 5.5 μm² in xz). The advantage of this method compared to monitoring a single depth profile z is a dramatic increase in the number of available sites that can be measured in two spatial dimensions xz with lateral scanning; therefore, the study demonstrates that two-dimensional monitoring of small-scale functional activity would also be feasible.