The ability to selectively pay attention to a particular stream of input in the environment and to ignore competing irrelevant sounds is of utmost importance in daily life. This challenge is epitomized by the well-known “Cocktail Party Problem”, which has fascinated psychologist, neuroscientists, engineers and computer scientists for decades. Yet, to date much remains unknown about the neural basis underlying this important capacity. Moreover, performance on this important cognitive task varies greatly across individuals and under different environmental conditions, and attention is also known to ‘wander’ and fluctuate over time.The current proposal is aimed at linking neural activity to behavior in a “Cocktail Party”-like situation, and to understanding the factors underlying variability in selective attention performance. Using non-invasive neurophysiological recordings in humans, I will test the hypothesis that top-down modulation of sensory processing is directly linked to selective attention performance and can explain variability in performance across individuals, stimulus-conditions and over time. I will further investigate the effects of neurofeedback training on top-down sensory modulation and the impact such training has on performance on selective attention tasks. The use of neurofeedback in this framework introduces a new approach for probing the attentional system and studying its operations, and will also contribute to improving currently available training regimes for enhancing attentional performance.Overall, this research project will afford new perspectives and a deeper understanding of the neural basis of selective attention behavior and the “Cocktail Party” problem. Its results will also have substantial clinical implications for studying attentional disorders, such as ADHD.