Predictive Coding Over the Lifespan: Increased Reliance on Perceptual Priors in Older Adults-A Magnetoencephalography and Dynamic Causal Modeling Study.

Michael Wibral,Patricia Wollstadt,Saskia Helbling,Jason S. Chan,Cerisa Stawowsky,Marcus J. Naumer,Jochen Kaiser,Mareike Brandl

doi:10.3389/fnagi.2021.631599

Michael Wibral, Patricia Wollstadt + Show 6 more

Open Access

https://doi.org/10.3389/fnagi.2021.631599

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Abstract

Aging is accompanied by unisensory decline. To compensate for this, two complementary strategies are potentially relied upon increasingly: first, older adults integrate more information from different sensory organs. Second, according to the predictive coding (PC) model, we form “templates” (internal models or “priors”) of the environment through our experiences. It is through increased life experience that older adults may rely more on these templates compared to younger adults. Multisensory integration and predictive coding would be effective strategies for the perception of near-threshold stimuli, which may however come at the cost of integrating irrelevant information. Both strategies can be studied in multisensory illusions because these require the integration of different sensory information, as well as an internal model of the world that can take precedence over sensory input. Here, we elicited a classic multisensory illusion, the sound-induced flash illusion, in younger (mean: 27 years, N = 25) and older (mean: 67 years, N = 28) adult participants while recording the magnetoencephalogram. Older adults perceived more illusions than younger adults. Older adults had increased pre-stimulus beta-band activity compared to younger adults as predicted by microcircuit theories of predictive coding, which suggest priors and predictions are linked to beta-band activity. Transfer entropy analysis and dynamic causal modeling of pre-stimulus magnetoencephalography data revealed a stronger illusion-related modulation of cross-modal connectivity from auditory to visual cortices in older compared to younger adults. We interpret this as the neural correlate of increased reliance on a cross-modal predictive template in older adults leading to the illusory percept.

Highlights

Predictive coding theory suggests that our perceptual experience is determined by a fine balance between internal predictions based on priors acquired over the course of our lives and incoming sensory evidence (Arnal and Giraud, 2012; Wolpe et al, 2016)
Previous studies have demonstrated that older adults as well as some patient populations have increased rates of illusory percepts, which can be interpreted as increased rates of multisensory integration
Predictive coding theories offer a parsimonious explanation for this effect, considering that the amount of accumulated prior information increases over the life-span, while the precision of unisensory evidence decreases

Summary

Introduction

Predictive coding theory suggests that our perceptual experience is determined by a fine balance between internal predictions based on priors acquired over the course of our lives and incoming sensory evidence (Arnal and Giraud, 2012; Wolpe et al, 2016). The first factor will strengthen the influence of predictions, while the second reduces the influence of unisensory evidence. Together, they should tip the balance to a state, where perception is increasingly dominated by predictions. They should tip the balance to a state, where perception is increasingly dominated by predictions Investigating this change in balance is possible using perceptual illusions that arise when predictions take precedence over sensory evidence, such as the sound-induced flash illusion (SiFi)

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