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Measuring brain hemodynamic changes in a songbird: responses to hypercapnia measured with functional MRI and near-infrared spectroscopy

C Vignal1,2, T Boumans3, B Montcel2, S Ramstein2, M Verhoye3, J Van Audekerke3, N Mathevon1,4, A Van der Linden3 and S Mottin2

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Songbirds have been evolved into models of choice for the study of the cerebral underpinnings of vocal communication. Nevertheless, there is still a need for in vivo methods allowing the real-time monitoring of brain activity. Functional Magnetic Resonance Imaging (fMRI) has been applied in anesthetized intact songbirds. It relies on blood oxygen level-dependent (BOLD) contrast revealing hemodynamic changes. Non-invasive near-infrared spectroscopy (NIRS) is based on the weak absorption of near-infrared light by biological tissues. Time-resolved femtosecond white laser NIRS is a new probing method using real-time spectral measurements which give access to the local variation of absorbing chromophores such as hemoglobins. In this study, we test the efficiency of our time-resolved NIRS device in monitoring physiological hemodynamic brain responses in a songbird, the zebra finch (Taeniopygia guttata), using a hypercapnia event (7% inhaled CO2). The results are compared to those obtained using BOLD fMRI. The NIRS measurements clearly demonstrate that during hypercapnia the blood oxygen saturation level increases (increase in local concentration of oxyhemoglobin, decrease in deoxyhemoglobin concentration and total hemoglobin concentration). Our results provide the first correlation in songbirds of the variations in total hemoglobin and oxygen saturation level obtained from NIRS with local BOLD signal variations.


 

For more information on this article, see medicalphysicsweb.org

PACS

43.66.Gf Detection and discrimination of sound by animals

87.19.U- Hemodynamics

87.61.Np Flow imaging

87.19.L- Neuroscience

42.62.Be Biological and medical applications

87.64.K- Spectroscopy

Subjects

Optics, quantum optics and lasers

Medical physics

Biological physics

Dates

Issue 10 (21 May 2008)

Received 16 October 2007, in final form 27 March 2008

Published 18 April 2008



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