Article

Journal of Membrane Biology

, Volume 231, Issue 1, pp 35-46

First online:

Optical Coherence Tomography Phase Measurement of Transient Changes in Squid Giant Axons During Activity

  • Taner AkkinAffiliated withDepartment of Biomedical Engineering, University of Minnesota Email author 
  • , David LandowneAffiliated withDepartment of Physiology and Biophysics, University of Miami
  • , Aarthi SivaprakasamAffiliated withDepartment of Biomedical Engineering, University of Minnesota

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Abstract

Noncontact optical measurements reveal that transient changes in squid giant axons are associated with action potential propagation and altered under different environmental (i.e., temperature) and physiological (i.e., ionic concentrations) conditions. Using a spectral-domain optical coherence tomography system, which produces real-time cross-sectional images of the axon in a nerve chamber, axonal surfaces along a depth profile are monitored. Differential phase analyses show transient changes around the membrane on a millisecond timescale, and the response is coincident with the arrival of the action potential at the optical measurement area. Cooling the axon slows the electrical and optical responses and increases the magnitude of the transient signals. Increasing the NaCl concentration bathing the axon, whose diameter is decreased in the hypertonic solution, results in significantly larger transient signals during action potential propagation. While monophasic and biphasic behaviors are observed, biphasic behavior dominates the results. The initial phase detected was constant for a single location but alternated for different locations; therefore, these transient signals acquired around the membrane appear to have local characteristics.

Keywords

Action potential Optical coherence tomography Phase measurement Functional neural imaging