Aging Modulates the Hemispheric Specialization during Word Production.

Elena Hoyau,Assia Jaillard,Alexandre Krainik,Cedric Pichat,Nathalie Fournet,Monica Baciu,Emilie Cousin,Naila Boudiaf

doi:10.3389/fnagi.2017.00125

Abstract

Although older adults exhibit normal accuracy in performing word retrieval and generation (lexical production; e.g., object naming), they are generally slower in responding than younger adults. To maintain accuracy, older adults recruit compensatory mechanisms and strategies. We focused on two such possible compensatory mechanisms, one semantic and one executive. These mechanisms are reflected at inter- and intra-hemispheric levels by various patterns of reorganization of lexical production cerebral networks. Hemispheric reorganization (HR) changes were also evaluated in relation to increase naming latencies. Using functional magnetic resonance imaging (fMRI), we examined 27 healthy participants (from 30 years to 85 years) during an object naming task, exploring and identifying task-related patterns of cerebral reorganization. We report two main results. First, we observed a left intra-hemispheric pattern of reorganization, the left anterior-posterior aging (LAPA) effect, consisting of supplementary activation of left posterior (temporo-parietal) regions in older adults and asymmetric activation along the left fronto-temporal axis. This pattern suggests that older adults recruit posterior semantic regions to perform object naming. The second finding consisted of bilateral recruitment of frontal regions to maintain appropriate response times, especially in older adults who were faster performers. This pattern is discussed in terms of compensatory mechanism. We suggest that aging is associated with multiple, co-existing compensation and reorganization mechanisms and patterns associated with lexical production.

Highlights

Anomia and tip-of-the-tongue phenomena are frequently reported by older adults in daily life (Perlmutter, 1978; Zelinski et al, 1980; Cavanaugh et al, 1983)
This section is structured in three parts: General results; Objective 1: Naming accuracy, and Objective 2: Naming latencies
We aimed to evaluate the effect of normal aging on lexical production, in terms of intra- and inter-Hemispheric reorganization (HR) (HR indices) of cerebral activation during an object naming task

Summary

Introduction

Anomia and tip-of-the-tongue phenomena are frequently reported by older adults in daily life (Perlmutter, 1978; Zelinski et al, 1980; Cavanaugh et al, 1983) They reflect difficulty in retrieving and generating words (Obler and Albert, 1980; Burke and Shafto, 2004; Salthouse and Mandell, 2013). At the cerebral level, aging modulates cerebral activity (Greenwood, 2007), reflected either by increased or decreased activity, or by additional recruitment of regions that are not usually engaged by similar tasks in younger adults (e.g., Cabeza, 2002; Greenwood, 2007; Park and Reuter-Lorenz, 2009; Lövdén et al, 2010; Grady, 2012) These modifications are reflected in multiple patterns of interand intra-hemispheric cerebral reorganization (e.g., Grady et al, 1994; Cabeza, 2002; Davis et al, 2008). We sought to determine whether the dissociation of naming performance in aging (i.e., preservation of naming accuracy despite longer latencies) is associated with intra- and inter-hemispheric cerebral reorganization mechanisms

Objectives

Methods

Results

Discussion

Conclusion