Perceptual Priming Can Increase or Decrease With Aging.

Kalathupiriyan A Zhivago,Ranjini Garani,S P Arun,Aditya Murthy,Simran Purokayastha,Sneha Shashidhara,Naren P Rao

doi:10.3389/fnagi.2020.576922

Abstract

A decline in declarative or explicit memory has been extensively characterized in cognitive aging and is a hallmark of cognitive impairments. However, whether and how implicit perceptual memory varies with aging or cognitive impairment is unclear. Here, we compared implicit perceptual memory and explicit memory measures in three groups of participants: (1) 59 healthy young volunteers (20–30 years); (2) 269 healthy old volunteers (50–90 years) and (3) 21 patients with mild cognitive impairment, i.e., MCI (50–90 years). To measure explicit memory, participants were tested on standard recognition and recall tasks. To measure implicit perceptual memory, we used a classic perceptual priming paradigm. Participants had to report the shape of a visual search pop-out target whose color or position was varied randomly across trials. Perceptual priming was measured as the speedup in response time for targets that repeated in color or position. Our main findings are as follows: (1) Explicit memory was weaker in old compared to young participants, and in MCI patients compared to age- and education-matched controls; (2) Surprisingly, perceptual priming did not always decline with age: color priming was smaller in older participants but position priming was larger; (3) Position priming was less frequent in the MCI group compared to matched controls; (4) Perceptual priming and explicit memory were uncorrelated across participants. Thus, perceptual priming can increase or decrease with age or cognitive impairment, but these changes do not covary with explicit memory.

Highlights

Memory has broadly been classified into explicit and implicit memory (Squire, 1992; Schacter et al, 1993; Gazzaniga et al, 2014)
In the implicit perceptual priming task (Figure 1A), participants had to report the shape of an oddball item in a hexagonal search array while its position or color was varied independently
Object recognition memory was significantly weaker in old compared to young participants (Figure 3A; average accuracy: 92 ± 1% for old, 96 ± 1 for young, cohen’s d = 0.49, z = 2.62, p < 0.05, rank-sum test) and in patients compared to matched controls (Figure 3A; average accuracy: 84 ± 1% for patients, 91 ± 1 for matched controls, cohen’s d = 0.89, z = 3.31, p < 0.005, rank-sum test)

Summary

Introduction

Memory has broadly been classified into explicit and implicit memory (Squire, 1992; Schacter et al, 1993; Gazzaniga et al, 2014). Implicit memory is unconscious and non-declarative; it is measured by the facilitation in the response to previously experienced items (Schacter et al, 1993; Fleischman et al, 2005; Spataro et al, 2016). Since a decline in explicit memory is a hallmark of both aging and cognitive disorders, the question of whether implicit memory is affected has been extensively investigated (Mitchell and Bruss, 2003; Fleischman, 2007; Berry et al, 2008; Ward et al, 2013). The results are mixed: explicit memory always shows a clear decline with age and cognitive

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