We applied near-infrared spectroscopy (NIRS) and electroencephalography (EEG) simultaneously on the mouse brain and investigated the hemodynamic response to epileptic episodes under pharmacologically driven seizure. γ-butyrolactone (GBL) and 4-aminopyridine (4-AP) were applied to induce absence and tonic-clonic seizures, respectively. The epileptic episodes were identified from the single-channel EEG, and the corresponding hemodynamic changes in different regions of the brain were characterized by multichannel frequency-domain NIRS. Our results are the following: (i) the oxyhemoglobin level increases in the case of GBL-treated mice but not 4-AP-treated mice compared to the predrug state; (ii) the dominant response to each absence seizure is a decrease in deoxyhemolobin; (iii) the phase shift between oxy- and deoxyhemoglobin reduces in GBL-treated mice but no 4-AP-treated mice; and (iv) the spatial correlation of hemodynamics increased significantly in 4-AP-treated mice but not in GBL-treated mice. Our results shows that spatiotemporal tracking of cerebral hemodynamics using NIRS can be successfully applied to the mouse brain in conjunction with electrophysiological recording, which will support the study of molecular, cellular, and network origin of neurovascular coupling in vivo.
We monitored cell viability and damage under femtosecond laser irradiation using aser weezers Raman pectroscopy
(LTRS) which is becoming a powerful tool for the analysis of biological materials. Femtosecond lasers are more
frequently used as a light source for optical tweezers since they enable nonlinear optical phenomena such as two-photon
absorption or second harmonic generation trapping. Femtosecond laser optical trapping similar to thee CW laser optical
trapping except that optical damage can be easily induced due to extremely high peak power of femtosecond pulses. We
monitored the Raman signal changes as a marker for optical damage. We used red blood cell (RBC) as a target sample
and first used the CW laser beams to trap the RBC from the bottom of the chamber. After the trapped RBC is moved to a
desired depth, we switched the laser mode to mode-locked mode and monitored the Raman signals as a function of the
laser irradiation time. It was observed that the Raman shift at 1543 cm-1 may be a good marker for optical damage both
for CW and femtosecond laser trapping.
In this study, we measured the optical properties of optical tissue phantoms and human tissues by measuring the
photon density distribution on the boundary of the phantoms and tissues and by using the Frequency-Domain DOT
(Diffuse optical tomography) system. A trust region nonlinear optimization method is used for the image reconstruction
in DOT. This method is a more elaborated Newton method which takes advantage of the classical Newton method and
the gradient descent method. The validity of this method is verified by reconstructing the optical properties from
phantom experiment and simulated data using the Frequency-Domain DOT system.
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