In vivo and noninvasive measurement of a songbird head’s optical properties

Abstract

By assessing the cerebral blood volume and the hemoglobin oxygen saturation level, near-infrared spectroscopy (NIRS) probes brain oxygenation, which reflects cerebral activity. To develop a noninvasive method monitoring the brain of a songbird, we use an original NIRS device, i.e., a white laser coupled with an ultrafast spectrotemporal detector of optical signals without wavelength scanning. We perform in vivo measurements of the absorption coefficient and the reduced scattering coefficient of the caudal nidopallium area of the head of a songbird (the zebra finch).

Noninvasive diffusive optical imaging of the auditory response to birdsong in the zebra finch

“…For this conversion we used differential path lengths measured from the zebra finch head (Ramstein et al 2005) and extinction coefficients measured from zebra finch hemoglobin rather than those reported for mammalian species to account for species-specific idiosyncrasies. The extinction coefficients were obtained for both HbO and HbR (Wray et al 1988; Hanash and Shapiro 1981).…”

“…Data were converted to hemodynamic measures using the Modified Beer Lambert Law (Wray et al 1988), which implicitly assigned all changes to absorption. The Modified Beer Lambert Law requires the use of several constants: the mean reduced scattering coefficient measured from zebra finch (Ramstein et al 2005) through a path estimated to go through the higher auditory areas NCM and field L is 4.857/mm. This was the best measured estimate we could use for this coefficient, and we used the same coefficient for all light paths although they may have passed through different tissue and geometry.…”

“…Development of the NIRS approach to study songbirds began with measurements of the optical properties of the zebra finch head by Ramstein et al (2005), and a comparison of optical and fMRI responses to hypercapnia (Vignal et al 2008). Responses to songs and calls have been demonstrated recently using a method termed Picosecond Optical Tomography, which affords picosecond and submillimeter resolution along a strip of tissue (Mottin et al 2011).…”

Diffuse optical tomography with an amplified ultrafast laser and a single-shot streak camera: application to real-time in vivo songbird neuro-imaging

“…fs) DOT has been proven to be a reliable tool for characterizing the optical properties of diffusive media like brain tissues: contrary to CW DOT where a single parameter is measured (i.e. the transmission), ultrafast DOT enables to access a whole distribution of photons times of flight, giving much more information on the optical and structure properties of the medium [7,8]. In particular in-depth scanning is foreseeable since each time of flight corresponds to a particular exploration volume (see Fig.…”

“…The x resolution is given by these imaging properties ; the z resolution could be estimated by the shape of the time of flight distribution. The use of a fs broadband white laser could also enables a λ resolution [8]. Only single wavelength procedures are described in this paper.…”