Alpha Activity Reflects the Magnitude of an Individual Bias in Human Perception

Abstract

Biases in sensory perception can arise from both experimental manipulations and personal traitlike features. These idiosyncratic biases and their neural underpinnings are often overlooked in studies on the physiology underlying perception. A potential candidate mechanism mediating such idiosyncratic biases is spontaneous alpha activity, a prominent brain rhythm known to influence the processing of upcoming information in general. Using a time perception task, we here tested the hypothesis that alpha power reflects the compensation for an idiosyncratic bias. Importantly, to understand the interplay between idiosyncratic biases and contextual (temporary) biases induced by experimental manipulations, we quantified this relation before and after temporal recalibration. Using EEG recordings in human participants, we found that pre-stimulus alpha power correlates with the tendency to respond relative to an own idiosyncratic bias, with stronger alpha leading to responses matching the bias. In contrast, alpha power did not predict response correctness. These results also held after temporal recalibration and were specific to the alpha band, suggesting that alpha power indexes the cognitive effort to overcome an individual's momentary bias in perception. Significance statementThe brain is a biased organ, frequently generating systematically distorted percepts of the world, leading each of us to evolve in our own subjective reality. However, such biases are often overlooked or considered noise when studying the neural mechanisms underlying perception. We show that spontaneous alpha band activity predicts the degree of biasedness of human choices in a time perception task, suggesting that alpha power indexes the effort needed to overcome an individual's idiosyncratic bias. This result provides a window onto the neural underpinnings of subjective perception, and offers the possibility to quantify or manipulate such priors in future studies.

The Neurophysiological Basis of the Trial-Wise and Cumulative Ventriloquism Aftereffects

“…We removed ICA components that reflect eye movement artefacts, localized muscle activity or poor electrode contacts (17.2 ± 4.45 rejected components per participant, mean ± SD). These were identified as in our previous studies (Grabot & Kayser, 2020;Kayser et al, 2017) following definitions provided in the literature (Hipp & Siegel, 2013;O'Beirne & Patuzzi, 1999). Additionally, trials with amplitude exceeding 175 mV were rejected.…”

Postdiction: when temporal regularity drives space perception through pre-stimulus alpha oscillations

“…Based on the assumption that postdiction is driven by prior expectations, and on previous literature indicating that the influence of priors on perception is reflected in low-frequency oscillatory activity (Sherman, Kanai, Seth, & VanRullen, 2016; Mayer, Schwiedrzik, Wibral, Singer, & Melloni, 2016; Samaha, Boutonnet, Postle, & Lupyan, 2018; Nuttida Rungratsameetaweemana & Serences, 2018), we hypothesized that perceptual reports during the rabbit illusion are similarly related to pre-stimulus oscillatory activity. We thus investigated pre-stimulus alpha activity through the prism of a recent line of research which has suggested a specific interpretation of the role of alpha band oscillations during perceptual decisions: alpha may reflect the influence of idiosyncratic biases on perception (Grabot & Kayser, 2019; Grabot, Kösem, Azizi, & Wassenhove, 2017) and may relate to the decision criterion rather than accuracy (Limbach & Corballis, 2016; Iemi, Chaumon, Crouzet, & Busch, 2017; Samaha, Iemi, & Postle, 2017; Craddock, Poliakoff, El-deredy, Klepousniotou, & Lloyd, 2017; Iemi & Busch, 2018). We found that pre-stimulus alpha power fluctuations in parietal and frontal areas reflect the tendency of an individual to perceive the illusion.…”

“…The regions found to be activated in the inward condition, fall within the motor and premotor cortex, known to play a central role in timing perception, especially in the momentarily indexing of ongoing time (Macar, Coull, & Vidal, 2006; Coull, Meck, & Cheng, 2011). Pre-stimulus alpha activity correlating with individual biases was also located in frontal areas, possibly related to cognitive control (Grabot & Kayser, 2019).…”

“…In fact, many studies have shown that alpha oscillations correlate with the perception of upcoming stimuli (Ergenoglu, et al, 2004; Hanslmayr, et al, 2007; van Dijk, Schoffelen, Oostenveld, & Jensen, 2008; Mathewson, Gratton, Fabiani, Beck, & Ro, 2009). Increased alpha power was notably associated with a stronger influence of idiosyncratic biases of individual observers (Grabot & Kayser, 2019; Grabot, Kösem, Azizi, & Wassenhove, 2017). Since these biases may come from individual prior expectation (de Lange, Heilbron, & Kok, 2018), we hypothesized that pre-stimulus alpha power would reflect the impact of the intrinsic prior involved in postdiction.…”

Time Perception through the Processing of Verb Tenses: An ERP study regarding Mental Time Travel

“…Moreover, recent studies propose that alpha brain oscillations may reflect the temporal sequence coordination of the associated neuronal representations. The underlying rhythmic neuronal oscillations operate as an attentional 'gatekeeper' that allocates priority to certain stimuli for WM storage by enabling an optimal signal-to-noise ratio; in this way, possible interference with conflicting sensory inputs (Freunberger et al, 2011;Grabot and Kayser, 2020;Jensen et al, 2014) is avoided or reduced. In this framework, a considerable body of evidence has highlighted a relationship between the alpha phase and timing in perception.…”