Do ongoing neural oscillations influence objective visual acuity, perceptual bias, or decision bias?

• Applicant: Professor Dr. Niko Busch
• Subject Area: Biological Psychology and Cognitive Neuroscience ; Human Cognitive and Systems Neuroscience
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 397060357

Neural oscillations are ubiquitous in electrophysiological recordings. In particular, oscillations in the alpha-band (10 Hz), the most dominant rhythm in human EEG, are an index of neuronal excitability. Previous studies have shown that the power of ongoing alpha oscillations at the moment of stimulus presentation is correlated with correct detection of near-threshold stimuli. The conventional interpretation of this finding has been that alpha oscillations, and thus neural excitability, modulate the accuracy of visual perception, i.e. the ability to distinguish signal and noise. Recent findings, however, suggest that alpha oscillations may instead modulate the bias in observers' perceptual decisions. The empirical basis for this far-reaching re-interpretation of the functional role of spontaneous brain activity needs to be substantiated. Furthermore, a bias in signal detection measures can have two very different underlying causes: a perceptual bias, which affects the subjective appearance of signal and noise, or a decision bias, which affects the strategic preference for a response option. Previous studies were unable to distinguish between these alternatives. In this project, I propose to study the effect of ongoing neural oscillations on visual perception. Specifically, the planned experiments are designed to test whether pre-stimulus oscillations affect objective accuracy, the subjective appearance of stimuli (perceptual bias), or strategic decision making (decision bias). To this end, I plan to analyze oscillations in human EEG using single-trial time-frequency analysis, and to study how they are related to perception and behavior using an innovative combination of psychophysics, signal detection theory, and computational modeling. Considering that spontaneous fluctuations in the strength of EEG oscillations are tightly correlated with neuronal excitability and with fluctuations in vigilance and performance, the findings of this project have implications for our understanding of the brain's ongoing regulation of arousal, wakefulness, and the maintenance of adequate perceptual and cognitive performance.

• DFG Programme: Research Grants