Аннотация:The paper explores the notion of PIU among adolescents and young adults and presents results of a pilot experimental research of physiological and cognitive changes influenced by poly-code Internet content. The purpose of the review part of the research is to fit into the scope of PIU conceptualization. The goal of the experimental part is to identify differences in perceptions of different stimuli modalities of poly-code Internet content. The results of the experiment support the idea that the perception of poly-code stimuli, both in the element-wise and in the complex modes, provides significant stress on the psycho-physiological and cognitive systems of the recipients. Differences in dynamics of the electroencephalogram spectral indices during perceptions of different stimuli modalities and in power ranges before and after each experimental probe indicate the fact that auditory and visual stimuli are perceived differently and have a different delayed effect on the state of the cerebral cortex. The results of review part of the research indicate methodological and content lacunae, which can be filled with the findings of a complex research, one of the results of which will be an augmented view of PIU taking into account the multimodal nature of the Internet environments and cognitive functions of web users in the process of multimodal Internet content perception.