Functional near-infrared spectroscopy (fNIRS) provides an alternative to functional magnetic resonance imaging (fMRI) for assessing changes in cortical hemodynamics. To establish the utility of fNIRS for measuring differential recruitment of the motor network during the production of timing-based actions, we measured cortical hemodynamic responses in 10 healthy adults while they performed two versions of a finger-tapping task. The task, used in an earlier fMRI study (Jantzen et al., 2004), was designed to track the neural basis of different timing behaviors. Participants paced their tapping to a metronomic tone, then continued tapping at the established pace without the tone. Initial tapping was either synchronous or syncopated relative to the tone. This produced a 2 × 2 design: synchronous or syncopated tapping and pacing the tapping with or continuing without a tone. Accuracy of the timing of tapping was tracked while cortical hemodynamics were monitored using fNIRS. Hemodynamic responses were computed by canonical statistical analysis across trials in each of the four conditions. Task-induced brain activation resulted in significant increases in oxygenated hemoglobin concentration (oxy-Hb) in a broad region in and around the motor cortex. Overall, syncopated tapping was harder behaviorally and produced more cortical activation than synchronous tapping. Thus, we observed significant changes in oxy-Hb in direct relation to the complexity of the task.
Attention is one of the brain's ability to focus on one particular issue among many others. Attention plays a critical role in those tasks that involve detection of rare events such as air traffic control where any attention lapses may cause a disaster. So, measurement and quantification of attention workload levels is critical and can be used to improve one's performance. In this article an effective algorithm for measurement of one's attention in three different levels by means of functional near-infrared spectroscopy is presented. Brain hemodynamic of 8 healthy subjects during a modified stroop color word task over the PFC region is measured using a 4-channel continuous wave functional near infrared spectroscopy (fNIRS) instrument. Since the hemodynamic response of mental activities is contaminated by psychological inferences, the first processing step is extraction of evoked hemodynamic response due to various attention levels. Then, an effective feature of hemodynamic response is extracted and analyzed by ANOVA test. The results of this study demonstrate the feasibility of fNIRS based attention level measurement that could provide valuable information of individuals' ability.
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