Measurement of neural functionality using phase sensitive optical coherence reflectometry

Abstract

Optical methods, devices, and systems for noninvasively detecting transient surface displacements in a neuron are disclosed. Methods, devices, and systems provided may employ a phase-sensitive optical low coherence reflectometer. In addition, surface displacements due to action potential propagation in neural tissues may be detected in some embodiments using back-reflected light. According to some embodiments, exogenous chemicals or reflect ion coatings are not required. Transient neural surface displacement of less than 1 nm in amplitude and 1 ms in duration may be detected and may be generally coincident with action potential arrival to the optical measurement site. The systems and methods may be used for noninvasive detection of various neuropathies such as retinal neuropathies. They may also be useful in detecting the effects of various pharmacological agents.

What is claimed is: 
     
         1 . A method of diagnosing a neuropathy comprising:
 a. assessing the transient surface displacement of a test neuron using a phase-sensitive optical reflectometer to obtain at least one surface displacement assessment;   b. comparing the at least one test neuron's surface displacement assessment with control surface displacement assessments to produce a test neuron activity differential; and   c. processing the test neuron activity differential to detect inappropriate neural activity in the test neuron, wherein the inappropriate neural activity is indicative of a neuropathy.   
     
     
         2 . The method of  claim 1 , wherein the surface displacement is about 0.1 nanometers. 
     
     
         3 . The method of  claim 1 , wherein the surface displacement includes a temporal resolution of about 0.1 microseconds. 
     
     
         4 . The method of  claim 1 , wherein the transient surface displacement Δp is calculated from the differential phase (Δφ) sensitivity and the center wavelength of the source (λo) using the equation: Δp=(λo/4π)Δφ. 
     
     
         5 . The method of  claim 1 , wherein the transient surface displacement includes displacement of one or more neural cell surfaces. 
     
     
         6 . The method of  claim 1 , wherein the processing step is operable to transform the detection of inappropriate neural activity into an indicator of a neuropathy in the neuron. 
     
     
         7 . The method of  claim 1 , further comprising measuring the transient retardation change by the measured intensity changes during an action potential propagation due to the transient retardation change ΔR=½ R (ΔI/I), where R is the retardation due to the resting birefringence and I is the resting intensity of light. 
     
     
         8 . The method of  claim 1 , further comprising measuring changes in form-birefringence by the transient surface displacement in response to rapid repetitive stimuli.