Fast Optical Neurophysiology
Simultaneous high spatial and temporal resolution brain imaging is the ultimate goal for many neurophysiological studies; however, no existing technique can provide all the information currently needed. Intrinsic optical properties of neural tissue have the potential to someday provide images of fast responses corresponding directly to neuronal activation with high spatial resolution. Most intrinsic optical procedures use slow metabolic changes in absorption or scattering. However, birefringence imaging techniques rely on changes in light polarization to record neural activity related to membrane potential. The largest responses result when the incident light is linearly polarized at 45 degrees with respect to the long axis of an isolated nerve. Further system optimizations can use multiple angles and incoherent light sources with narrow bandwidths in order to reduce background noise and increase signal contrast. We have explored methods for obtaining fast optical signals in vivo occurring tens to hundreds of milliseconds after stimulation based on several physiological components that may contribute to the optical changes. Our aim is to employ birefringence techniques in vivo in order to reduce background noise, increase signal contrast, and record optical responses concomitant with the electrical correlates of neural activation.
KeywordsNeural Activity Polarization Signal Nerve Bundle Outer Sheath Squid Giant Axon
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