Mistaking imagination for reality: Congruent mental imagery leads to more liberal perceptual detection

Nadine Dijkstra,Matan Mazor,Peter Kok,Stephen Fleming

doi:10.1016/j.cognition.2021.104719

Nadine Dijkstra, Matan Mazor + Show 2 more

Open Access

https://doi.org/10.1016/j.cognition.2021.104719

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Abstract

Visual experiences can be triggered externally, by signals coming from the outside world during perception; or internally, by signals from memory during mental imagery. Imagery and perception activate similar neural codes in sensory areas, suggesting that they might sometimes be confused. In the current study, we investigated whether imagery influences perception by instructing participants to imagine gratings while externally detecting these same gratings at threshold. In a series of three experiments, we showed that imagery led to a more liberal criterion for reporting stimulus presence, and that this effect was both independent of expectation and stimulus-specific. Furthermore, participants with more vivid imagery were generally more likely to report the presence of external stimuli, independent of condition. The results can be explained as either a low-level sensory or a high-level decision-making effect. We discuss that the most likely explanation is that during imagery, internally generated sensory signals are sometimes confused for perception and suggest how the underlying mechanisms can be further characterized in future research. Our findings show that imagery and perception interact and emphasize that internally and externally generated signals are combined in complex ways to determine conscious perception.

Highlights

In daily life, we are bombarded with visual input from the outside world
Various lines of research have shown that externally triggered perception and internally triggered mental imagery activate similar neural codes in sensory as well as high-level brain areas, even in the presence of external input (Rademaker, Chunharas, & Serences, 2019; but see Bettencourt & Xu, 2015). This leads to the hypothesis that engaging in imagery might influence how the brain processes external inputs during perception
In a series of experiments, we investigated the influence of imagery on signal detection theoretic measures of detection and whether this effect was influenced by expectation, was stimulus-specific and whether individual differences in imagery vividness played a role

Summary

Introduction

We are bombarded with visual input from the outside world. Different shapes, colours and textures are processed by our visual system to create the technicolour perception we experience every day. Various lines of research have shown that externally triggered perception and internally triggered mental imagery activate similar neural codes in sensory as well as high-level brain areas (for reviews, see Dijkstra, Bosch, & van Gerven, 2019; Pearson, 2019), even in the presence of external input (Rademaker, Chunharas, & Serences, 2019; but see Bettencourt & Xu, 2015). This leads to the hypothesis that engaging in imagery might influence how the brain processes external inputs during perception. These results can be explained by the idea that imagery functions as a top-down prior, biasing perception towards or away from the imagined percept by pre-activating stimulus-specific neural pop ulations, similar to the effects of expectation (Denison, Piazza, & Silver, 2011; Dijkstra, Hinne, et al, 2019; Hohwy, Roepstorff, & Friston, 2008)

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