Opposing Effects of Ongoing Alpha-Band Activity on Magno- and Parvo-Mediated Detection

Spontaneous occipital alpha-band activity (8-12 Hz) has been shown to influence perceptual variability, leading one to report seeing a stimulus more often during states of weak alpha power, likely due to a shift in detection criterion. However, prior work has paid little attention to the specific stimulus properties mediating detection. In early vision, different stimulus properties are preferentially processed along the magnocellular (MC) and parvocellular (PC) pathways, which vary in their preference for spatial and temporal frequency and chromatic information. The goal of this study was to understand how spontaneous alpha power effects the detection of stimuli which are preferentially processed by either the MC or PC pathway. To achieve this, we used the “Steady/Pulsed Paradigm” which presented a brief, near-threshold stimulus in two conditions intended to bias processing to one or the other pathway. The pulsed condition presents the target stimulus atop a luminance pedestal, whose transient onset is believed to saturate MC firing and bias detection to the PC pathway. In the steady condition, which more closely resembles canonical detection paradigms, the luminance pedestals are present throughout the entire trial which is thought to evoke a sustained response from the PC pathway, biasing detection towards the MC pathway. Our results showed an interaction effect of alpha power on detection between the two conditions. While weak alpha power was predictive of seeing the stimulus in the steady condition (MC-biased), the opposite was found in the case of the pulsed condition (PC-biased). This interaction was driven by opposing alpha-related criterion shifts between the two tasks, suggesting that alpha oscillations may deferentially regulate excitability in the MC and PC pathways.