The present study attempts to better identify the neurophysiological changes occurring during flow experience and how this can be related to the mobilization of attentional resources. Self-reports of flow (using a flow feelings scale) and attention (using thought probes), autonomic activity (heart rate, heart rate variability, and breathing rate), and cerebral oxygenation (using near-infrared spectroscopy) in two regions of the frontoparietal attention network (right lateral frontal cortex and right inferior parietal lobe) were measured during the practice of two simple video games (Tetris and Pong) played at different difficulty conditions (easy, optimal, hard, or self-selected). Our results indicated that an optimal level of difficulty, compared with an easy or hard level of difficulty led to greater flow feelings and a higher concentration of oxygenated hemoglobin in the regions of the frontoparietal network. The self-selected, named autonomy condition did not lead to more flow feelings than the optimal condition; however, the autonomy condition led to greater sympathetic activity (reduced heart rate variability and greater breathing rate) and higher activation of the frontoparietal regions. Our study suggests that flow feelings are highly connected to the mobilization of attentional resources, and all the more in a condition that promotes individuals' choice and autonomy.