Biology subjects

Pilipenko, A.

Publications and source records attributed to Pilipenko, A..

3 recordsLinked to original sources

bioRxiv2024

Metacognition in Putative Magno- and Parvocellular Vision

A major distinction in early visual processing is the magnocellular (MC) and parvocellular (PC) pathways. The MC pathway preferentially processes motion, transient events, and low spatial frequencies, while the PC pathway preferentially processes color, sustained events, and high spatial frequencies. Prior work has theorized that the PC pathway more strongly contributes to conscious object recognition via projections to the ventral "what" visual pathway, whereas the MC pathway underlies non-conscious, action-oriented motion and localization processing via the dorsal stream "where/how" pathway. This invites the question: Are we equally aware of activity in both pathways? And if not, do task demands interact with which pathway is more accessible to awareness? We investigated this question in a set of two studies measuring participants metacognition for stimuli biased towards MC or PC processing. The "Steady/Pulsed Paradigm" presents brief stimuli under two conditions thought to favor either pathway. In the "pulsed" condition, the target appears atop a strong luminance pedestal which theoretically saturates the transient MC response and leaves the PC pathway to process the stimulus. In the "steady" condition, the stimulus is identical except the luminance pedestal is constant throughout the trial, rather than flashed alongside the target. This theoretically adapts the PC neurons and leaves MC for processing. Experiment 1 was a spatial localization task thought to rely on information relayed from the MC pathway. Using both a model-based and model-free approach to quantify participants metacognitive sensitivity to their own task performance, we found greater metacognition in the steady (MC-biased) condition. Experiment 2 was a fine-grained orientation-discrimination task more reliant on PC pathway information. Our results show an abolishment of the MC pathway advantage seen in Experiment 1 and suggest that the metacognitive advantage for MC processing may hold for stimulus localization tasks only. More generally, our results highlight the need to consider the possibility of differential access to low-level stimulus properties in studies of visual metacognition

animal behavior and cognition↗

bioRxiv2024

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

Spontaneous fluctuations in cortical excitability, as reflected in variation in occipital alpha-band activity (8-12 Hz), have been shown to explain trial-to-trial variability in perception. Specifically, observers typically 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 content and chromatic information. The goal of this study was to understand how spontaneous alpha power affects 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. Our results showed an interaction effect of pre-stimulus alpha power on detection between the two conditions. While weak alpha power was predictive of seeing the stimulus in the steady condition (MC-biased), no significant effect was found in the pulsed condition (PC-biased). This interaction was driven by a selective alpha-related criterion shift in the steady condition, with no effect of pre-stimulus alpha on sensitivity (d) in either condition. Our results imply that alpha oscillations may differentially regulate excitability in the MC and PC pathways.

neuroscience↗

bioRxiv2023

Double dissociation of spontaneous alpha-band activity and pupil-linked arousal on additive and multiplicative perceptual gain

Perception is a probabilistic process dependent on external stimulus properties and ones internal state. However, which internal states influence perception and via what mechanisms remain debated. We studied how spontaneous alpha-band activity (8-12 Hz) and pupil fluctuations impact visual detection and confidence across stimulus contrast levels (i.e., the contrast response function or CRF). We found that weak pre-stimulus alpha power induced an "additive" shift in the CRF, whereby stimuli were reported present more frequently at all contrast levels, including contrast of zero (i.e., false alarms). Conversely, pre-stimulus pupil size had a "multiplicative" effect on detection such that stimuli occurring during large pupil states (putatively corresponding to higher arousal) were perceived more frequently as contrast increased. Signal detection modeling reveals that alpha power changes detection criteria equally across the CRF but not detection sensitivity (d) whereas pupil-linked arousal modulated sensitivity, particularly for higher contrasts. Interestingly, pupil size and alpha power were positively correlated, meaning that some of the effect of alpha on detection may be mediated by pupil fluctuations. However, pupil-independent alpha still induced an additive shift in the CRF corresponding to a criterion effect. Our data imply that weak alpha boosts detection and confidence by an additive factor, rather than by a multiplicative scaling of contrast responses, a profile which captures the effect of pupil-linked arousal. We suggest that alpha-power and arousal fluctuations have dissociable effects on behavior. Alpha reflects the baseline level of visual excitability, which can vary independent of arousal. Significance statementNearly a century ago, brain waves around 8-13 Hz (the "alpha-band") were discovered and linked to visual processing and cortical arousal. However, the precise way that alpha activity shapes perception and relates to arousal is unsettled. We recorded pupillometry and EEG while subjects detected and reported confidence for visual stimuli with varying intensity. Stimuli occurring during states of strong alpha were seen less often, regardless of intensity level, suggesting alpha exerts subtractive inhibition on perception and confidence. Pupil size (a proxy for arousal) was found to correlate with alpha yet, surprisingly, has a different effect on perception. Small pupil lowered perceptual sensitivity more as stimulus intensity increased. Our findings reveal distinct effects of alpha activity and arousal on visual perception.

neuroscience↗