The Role of Alpha Oscillations in Perceiving Visual Durations

An individual’s alpha-band oscillation (IAF) has long been proposed as a temporal clocking mechanism for estimating event durations, however mixed findings and limited use of task types and duration ranges have hampered strong conclusions. This EEG study measured performance on a battery of timing tasks to evaluate whether IAF is associated with the estimation and discrimination of visual event durations. In a temporal estimation task, participants reported the duration of a single stimulus presented between 300-1200ms. In a temporal discrimination task, participants were asked to report which of two stimuli was longer: a standard stimulus (100, 600, or 1200ms) or a comparison stimulus (50-150% of the standard). Stimuli also varied in whether they were constant luminance (“static” condition) or varied randomly in luminance within a trial (“dynamic” condition). Finally, the critical flicker frequency (CFF) was measured since several studies have shown the CFF to be correlated with IAF in clinical populations. We found that the average absolute error in duration estimates was moderately negatively correlated with IAF, suggesting that higher IAF is related to better accuracy when estimating visual durations. Psychometric functions fit to the discrimination task data revealed IAF had a low to moderate positive correlation with slope parameter, indicating that higher IAF is related to greater sensitivity in duration discrimination, with stronger effects for static stimuli. Interestingly, the CFF was moderately correlated with duration discrimination sensitivity for the longer standards (600ms and 1200ms), despite a lack of overall correlation between IAF and CFF. These results seem to suggest that IAF plays a role in duration perception, but to different degrees depending on the type of stimuli. Further analyses will measure alpha frequency at the trial level to examine whether moment-to-moment fluctuations in IAF bias duration perception.