Optical detection of brain activity using plasmonic ellipsometry technique

In spite of the existence of many techniques in the field of neural signal recording and mapping, the realm for emergence of novel methods is still open. One of the novel methods that attracts the researchers attention is neuroplasmonics which benefits from the voltage-sensitive plasmonics. However, this field faces two main ambiguities: the physical mechanism of voltage-sensitive sensing of plasmonics and second, the strength of recorded responses. In this paper, after replying briefly the first question, we go forward by proposing ellipsometry measurements as a strong and very sensitive characterization method for voltage-sensitive plasmonics. Here, the suggested parameter of effective delta (i.e. delta contrast) creates the opportunity to distinguish clearly the results of applying different voltages to biological solutions (i.e. Phosphate Buffer Solution and artificial Cerebrospinal Fluid) and brain tissue (i.e. cerebellum tissue). The strong response of effective delta for cerebellum tissue indicates that the stimulation of brain tissue via external potential redistributes the charges at the interface of metal and modulates its dielectric constant at Thomson-Fermi layer which subsequently, leads to the variation in surface plasmon resonance signal. (C) 2017 Elsevier B.V. All rights reserved.