Título del libro: Neurophotonics And Brain Mapping
Título del capítulo: Functional near-infrared spectroscopy in search of the fast optical signal
FRANCISCO RAFAEL FERNANDEZ DE MIGUEL; PAOLA BALLESTEROS ZEBADUA; JAVIER EDGAR FRANCO PEREZ; MIGUEL ANGEL CELIS LOPEZ;
Autores externos:
Idioma:
Inglés
Año de publicación:
2017
Palabras clave:
Brain; Chemical activation; Chromophores; Hemodynamics; Infrared devices; Infrared radiation; Near infrared spectroscopy; Neurons; Optical image storage; Refractive index; Tissue; Tissue engineering; Absorption and scatterings; Chromophore concentrations; Diffuse optical imaging (DOI); Functional near infrared spectroscopy; Functional near-infrared spectroscopy (fnirs); Neuro-vascular coupling; Numerical reconstruction; Spectroscopic signatures; Functional neuroimaging
Resumen:
Diffuse optical imaging (DOI) is an emerging modality of medical imaging based on the use of nearinfrared light. This technique permits to study living tissue noninvasively (Villringer and Chance 1997; Strangman et al. 2002). Its working principle capitalizes on the characteristic spectroscopic signatures of the molecules of interest. Its practical manifestation involves irradiating a narrow collimated beam over the biological tissue, where the light is scattered, and in response, part of it abandons the tissue to be collected by a detector. The sensed light encodes information about the physiological changes in the tissue in the form of changes in absorption and scattering. In the adult head, DOI becomes a practical form of functional neuroimaging known as functional near-infrared spectroscopy (fNIRS). Optical imaging is currently the only neuroimaging modality with the potential to measure both the direct neural activity and the indirect hemodynamic responses manifested through the neurovascular coupling. The physiological changes resulting from brain activity can be split in three stages (Villringer and Chance 1997; Franceschini and Boas 2004) with different latencies. First, the neuronal membrane potential is altered, which in turn changes the index of refraction at this boundary. This occurs just a few milliseconds (50?150 ms) after the initiation of the activation episode and is commonly referred to as fast optical signal (FOS). Second, the change in membrane potential is followed by a flux of ions and water associated with a glial swelling, which further affects the scattering of the tissue. The latency of this signal is between 0.5 and 1 s. Finally, the neural activity induces an arteriolar vasodilation and subsequently an increase in the regional cerebral blood flow. This late hemodynamic response is referred to as neurovascular coupling, and it is manifested a few seconds (2?5 s) after the onset of brain activation. The typical hemodynamic response starts with a small increase in deoxyhemoglobin (HHb), followed by a much larger increase of the oxyhemoglobin (HbO2) (Orihuela-Espina et al. 2010). These changes in chromophore concentration alter the absorption properties of the tissue. The affectation of the tissue?s optical properties in all stages means that fNIRS is a suitable candidate for observing the brain activity directly, or more commonly the hemodynamic response. This chapter will discuss the underlying principles that govern optical imaging using infrared radiation in instrumental and in numerical reconstruction efforts to pave the way for an effective direct observation of neural activity through the FOS. © 2017 by Taylor & Francis Group, LLC.
Entidades citadas de la UNAM:
ISBN:
9781482236866
Editorial:
CRC Press Nombre de la publicación:
Functional near-infrared spectroscopy in search of the fast optical signal
Página inicial:
77
Página final:
99
