Boosts in brain signal variability track liberal shifts in decision bias.

Niels A Kloosterman,Johannes Jacobus Fahrenfort,Douglas D Garrett,Ulman Lindenberger,Julian Q Kosciessa

doi:10.7554/elife.54201

Niels A Kloosterman, Johannes Jacobus Fahrenfort + Show 3 more

Open Access

https://doi.org/10.7554/elife.54201

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Abstract

Adopting particular decision biases allows organisms to tailor their choices to environmental demands. For example, a liberal response strategy pays off when target detection is crucial, whereas a conservative strategy is optimal for avoiding false alarms. Using conventional time-frequency analysis of human electroencephalographic (EEG) activity, we previously showed that bias setting entails adjustment of evidence accumulation in sensory regions (Kloosterman et al., 2019), but the presumed prefrontal signature of a conservative-to-liberal bias shift has remained elusive. Here, we show that a liberal bias shift is reflected in a more unconstrained neural regime (boosted entropy) in frontal regions that is suited to the detection of unpredictable events. Overall EEG variation, spectral power and event-related potentials could not explain this relationship, highlighting that moment-to-moment neural variability uniquely tracks bias shifts. Neural variability modulation through prefrontal cortex appears instrumental for permitting an organism to adapt its biases to environmental demands.

Highlights

We often reach decisions by objectively weighing different alternatives, and by allowing subjective biases to influence our choices
We developed time-resolved, modified multi-scale entropy (MSE), that differs from traditional MSE in two ways
Frontal cortex has previously been shown to be involved in strategic bias shifts in humans (Chen et al, 2015b; Rahnev et al, 2016b; Reckless et al, 2014b; Windmann et al, 2002b) and monkeys (Ferrera et al, 2009), but its spatiotemporal neural signature has to date remained elusive

Summary

Introduction

We often reach decisions by objectively weighing different alternatives, and by allowing subjective biases to influence our choices. Stronger quenching has been reported in observers with higher perceptual sensitivity (Arazi et al, 2017), in line with a central assumption of signal detection theory (SDT) that internal noise is detrimental for sensitivity and should be suppressed (Green and Swets, 1966) To attend to this conceptual discrepancy, we asked whether a quenching effect can be observed in moment-to-variability, and if so, whether it reflects strategic decision bias shifts and perceptual sensitivity. We found that those participants who strategically shifted more towards a liberal bias, showed a stronger boost in mMSE This relationship could not be explained by overall EEG signal variation, band-specific spectral power, and eventrelated potentials, highlighting the unique contribution of moment-to-moment neural variability to the bias shift. We show that interactions between spectral power and phase in ultra-low frequencies (1-3 Hz) may underlie the observed effects

Results

Discussion

Materials and Methods