Feature-specific reactivations of past information shift current neural encoding thereby mediating serial bias behaviors

Abstract

The regularities of the world render an intricate interplay between past and present. Even across independent trials, current-trial perception can be automatically shifted by preceding trials, namely the “serial bias.” Meanwhile, the neural implementation of the spontaneous shift of present by past that operates on multiple features remains unknown. In two auditory categorization experiments with human electrophysiological recordings, we demonstrate that serial bias arises from the co-occurrence of past-trial neural reactivation and the neural encoding of current-trial features. The meeting of past and present shifts the neural representation of current-trial features and modulates serial bias behavior. Critically, past-trial features (i.e., pitch, category choice, motor response) keep their respective identities in memory and are only reactivated by the corresponding features in the current trial, giving rise to dissociated feature-specific serial biases. The feature-specific automatic reactivation might constitute a fundamental mechanism for adaptive past-to-present generalizations over multiple features.

Reactivated past decisions repel early sensory processing and attract late decision-making

“…PFC recordings on monkeys show that past-trial information is transiently reactivated just before trial onset and further correlates with serial bias behavior 28 . Our recent study 19 as well as previous works [31][32][33][34] demonstrate that past-trial information, indeed retained in activity-silent states during the intertrial interval, is triggered by the corresponding event within the current trial, and the co-occurrence of past and present contributes to serial bias. Most importantly, the past-to-present neural influence exhibits a feature-specific direction commensurate with the corresponding bias behavior, i.e., repulsive for sensory and motor features, and attractive for choices 19 .…”

“…Our recent study 19 as well as previous works [31][32][33][34] demonstrate that past-trial information, indeed retained in activity-silent states during the intertrial interval, is triggered by the corresponding event within the current trial, and the co-occurrence of past and present contributes to serial bias. Most importantly, the past-to-present neural influence exhibits a feature-specific direction commensurate with the corresponding bias behavior, i.e., repulsive for sensory and motor features, and attractive for choices 19 . Serial bias is also posited to depend on neural representational similarities between sensory and memory information 35 , such as aligned and flipped relationships resulting in attractive and repulsive serial bias 26,33 .…”

“…Both repulsive and attractive past-present interactions rely on memory reactivations of past. Consistent with the 'activity-silent' WM theory 49 , recent studies show that past-trial information silently stored in WM could be reactivated either before stimulus onset or after 19,28,[31][32][33][34]50 . Here, only pasttrial information that contributes to serial bias behaviors is reactivated, suggesting a substantial role of memory reactivation in serial dependence.…”

“…Notably, our previous study revealed feature-specific characteristics of past reactivation, i.e., reactivated by corresponding features 19 . Meanwhile, since it is an instantaneous perceptual decision-making task where sensory encoding and decision-making co-evolve, the stages for these feature-specific reactivations could not be identified.…”

“…One striking example is serial dependence, that is, perception tends to be involuntarily biased towards stimuli in previous trials [4][5][6][7][8] . Serial dependence has been robustly observed in a wide range of visual features, from simple ones like orientation 4,[9][10][11][12] , numerosity 13 , and position 14,15 to abstract ones such as facial attractiveness 16,17 and other modalities 18,19 . Despite its detrimental effects on perceptual fidelity, serial dependence is thought to reflect an optimizing strategy of the brain to increase perceptual stability and efficiency by taking advantage of inherent temporal correlations in a world that is presumably stable over a short time scale 20,21 .…”