Biomedical Engineering Reference
In-Depth Information
Chapter 6
Using the Light Scattering Component of Optical Intrinsic
Signals to Visualize In Vivo Functional Structures of Neural
Tissues
Uma Maheswari Rajagopalan, Kazushige Tsunoda, and Manabu Tanifuji
Abstract
Visualization of changes in reflected light from
in vivo
brain tissues reveals spatial patterns of neural
activity. An important factor which influences the degree of light reflected includes the change in light
scattering elicited by neural activation. Microstructures of neural tissues generally cause light scattering,
and neural activities are associated with some changes in the microstructures. Here, we show that the
optical properties unique to light scattering enable us to visualize spatial patterns of retinal activity non-
invasively (FRG: functional retinography), and resolve functional structures in depth (fOCT: functional
optical coherence tomography).
Key words:
Intrinisic signal imaging, OCT, optical coherence tomography, light scattering.
1. Introduction
In 1986, Blasdel and Salame visualized orientation columns in
monkey visual cortex
in vivo
by staining the brain surface with a
voltage-sensitive dye and observed spatial patterns of absorption
changes elicited during visual stimuli
(1)
. After this initial finding,
it has been shown that functional structures can also be visualized
intrinsically, by measuring changes in light reflection without the
need for dyes
(2)
. This technique, the measurement of intrinsic
reflection changes elicited by neural activation, is called optical
intrinsic signal imaging (OISI), and is widely used to map corti-
cal functional structures in neural tissues of living animals
(3-9)
.
Because the intrinsic signals were originally found as byproduct
