Effect of prolonged stimulation on cerebral hemodynamic: A time-resolved fNIRS study

Purpose: Sustained attention is one of the most important cognitive abilities for the management of everyday life, but it is often studied only at the behavioral level, while functional correlates are scarcely investigated. In this article, the authors address the topic of characterizing the dynamics of cerebral metabolism in the prefrontal cortex during a task of prolonged attention. Method: By means of multichannel time-resolved functional near-infrared spectroscopy and generalized linear model based data processing, the authors measured the hemodynamic response of the prefrontal cortex from 19 healthy Subjects to a shortened version of a sustained attention task (Conners' Continuous Performance Test), lasting for 10 min. Results: The task elicited significant brain activation, which did not remain constant for the entire task, but showed a drop not correlated with performance decay 4 min after the beginning of the task. Furthermore, oxygenated hemoglobin showed an increasing trend also during the first phase of the recovery, just after the end of the task. Conclusion: The results indicate a nontrivial dynamics of neural activation, habituation processes, and hemodynamic/metabolic coupling. These results encourage further studies about continuous stimulation of cognitive functions on both healthy and pathological subjects. (C) 2009 American Association of Physicists in Medicine. [DOI: 10.1118/1.3190557]