Recent technological advancements in optical spectroscopy allow for the construction of hyperspectral (broadband) portable tissue oximeters. In a series of our recent papers we have shown that hyperspectral NIRS (hNIRS) has similar or better capabilities in the absolute tissue oximetry as frequency-domain NIRS, and that hNIRS is also very efficient in measuring temporal changes in tissue hemoglobin concentration and oxygenation. In this paper, we extend the application of hNIRS to the measurement of event-related hemodynamic and metabolic functional cerebral responses during simulated driving. In order to check if hNIRS can detect eventrelated changes in the brain, we measured the concentration changes of oxygenated (HbO 2 ) and deoxygenated (HHb) hemoglobin and of the oxidized state of cytochrome c oxidase, on the right and left prefrontal cortices (PFC) simultaneously during simulated driving on sixteen healthy right-handed participants (aged between 22-32). We used our in-house hNIRS system based on a portable spectrometer with cooled CCD detector and a driving simulator with a fully functional steering wheel and foot pedals. Each participant performed different driving tasks and participants were distracted during some driving conditions by asking general knowledge true/false questions. Our findings suggest that more complex driving tasks (non-distracted) deactivate PFC while distractions during driving significantly activate PFC, which is in agreement with previous fMRI results. Also, we found the changes in the redox state of the cytochrome C oxidase to be very consistent with those in the concentrations of HbO 2 and HHb. Overall our findings suggest that in addition to the suitability of absolute tissue oximetry, hyperspectral NIRS may also offer advantages in functional brain imaging. In particular, it can be used to measure the metabolic functional brain activity during actual driving.

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technique that used near-infrared light to measure concentrations of tissue chromophores 8 according to their absorption coefficients. In the near-infrared window (650-1,050 nm), the main tissue chromophores are HbO2, HHb, water and oxidized cytochrome-c-oxidase (Cyt-ox; an intracellular oxygen metabolism index), among which water has the smallest and Cyt-ox has the greatest molar absorption. 9 Current commercial NIRS systems use only a few wavelengths in the near-infrared window, known as multispectral NIRS (mNIRS). Advancements in NIRS technology now utilize the whole near-infrared window, known as broadband or hyperspectral NIRS (hNIRS). 10, 11 Both HbO2 and HHb are the intravascular chromophores reflecting oxygen delivery and have relatively high concentrations, which makes them easier to measure. 12 Cyt-ox is the terminal enzyme in the mitochondrial electron transport chain that converts oxygen into water, leading to the production of adenosine triphosphate; 13 thus, measuring the redox changes of Cyt-ox represents the level of intracellular aerobic metabolism. Non-invasive measurement of C ardiac arrest (CA) is an abrupt and unexpected condition that results in the sudden drop in cardiac output and consequently cerebral perfusion. Approximately two-thirds of CA patients die from neurological injuries, which are due to prolonged cerebral ischemia and subsequent reperfusion despite cardiopulmonary resuscitation (CPR). 1,2 Accurate measurement of cerebral oxygenation and metabolism during CA and CPR can provide important information on the cerebral response to CPR during CA, and test the effects of other resuscitation interventions. Near-infrared spectroscopy (NIRS) as a portable and non-invasive imaging technique is a good candidate for monitoring cerebral oxygenation under critical conditions such as CA. 3 However, current NIRS technology has been evaluated in small observational CA studies with variable results. 4-7Near-infrared spectroscopy has been progressively used for measurements of cerebral oxygenated hemoglobin Background: Maintaining cerebral oxygen delivery and metabolism during cardiac arrest (CA) through resuscitation is essential to improve the survival rate while avoiding brain injury. The effect of CA and cardiopulmonary resuscitation (CPR) on cerebral and muscle oxygen delivery and metabolism is not clearly quantified.

Objectives: Epinephrine is routinely administered to sudden cardiac arrest patients during resuscitation, but the neurologic effects on patients treated with epinephrine are not well understood. This study aims to assess the cerebral oxygenation and metabolism during ventricular fibrillation cardiac arrest, cardiopulmonary resuscitation, and epinephrine administration. Design: To investigate the effects of equal dosages of IV epinephrine administrated following sudden cardiac arrest as a continuous infusion or successive boluses during cardiopulmonary resuscitation, we monitored cerebral oxygenation and metabolism using hyperspectral near-infrared spectroscopy. Settings: A randomized laboratory animal study. Subjects: Nine healthy pigs. Interventions: None. Measurements and Main Results: Our study showed that although continuous epinephrine administration had no significant impact on overall cerebral hemodynamics, epinephrine boluses transiently improved cerebral oxygenation (oxygenated hemoglobin) and metabolism (cytochrome c oxidase) by 15% ± 6.7% and 49% ± 18%, respectively (p < 0.05) compared with the baseline (untreated) ventricular fibrillation. Our results suggest that the effects of epinephrine diminish with successive boluses as the impact of the third bolus on brain oxygen metabolism was 24.6% ± 3.8% less than that of the first two boluses. Conclusions: Epinephrine administration by bolus resulted in transient improvements in cerebral oxygenation and metabolism, whereas continuous epinephrine infusion did not, compared with placebo. Future studies are needed to evaluate and optimize the use of epinephrine in cardiac arrest resuscitation, particularly the dose, timing, and mode of administration.