Age effects on load-dependent brain activations in working memory for novel material

Abstract

Three competing models of cognitive aging (neural compensation, capacity limitations, neural inefficiency) were examined in relation to working memory for novel non-verbal material. To accomplish this goal young (n=25) and old (n=25) participants performed a delayed item recognition (DIR) task while being scanned with bold fMRI. The stimuli in the DIR task consisted of computergenerated closed-curve shapes with each shape presented only once in the testing conditions of each participant. This ensured that both the novelty and appearance of the shapes maximized visual demands and limited the extent of phonologic processing. Behaviorally, as expected, the old participants were slower and less accurate compared to the young participants. Spatial patterns of brain activation that corresponded to load-dependent (stimulus set size ranged from 1 to 3) fMRI signal during the three phases of the DIR task (memory set presentation, retention delay, probe presentation) were evaluated in both age groups. Support for neural compensation and capacity limitation was evident in retention delay and the probe phase, respectively. Data were inconsistent with the neural inefficiency model. The process specific support for the theories we examined is consistent with a large corpus of research showing that the substrates underlying the encoding, retention and probe phases are different. That is, cognitive aging theories can be specific to the neural networks/regions underlying the different phases of working memory. Delineating how these theories work in concert can increase knowledge of age-related effects on working memory. KeywordsAging; Working memory; neural compensation; neural capacity; inefficiency Correspondence: Roee Holtzer, Ph.D. Ferkauf Graduate School of Psychology and Department of Neurology, Albert Einstein College of Medicine, Yeshiva University, NY, USA. Phone: 718 430-3962; Fax: 718 430-3960; email: E-mail: rholtzer@aecom.yu.edu. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access Author ManuscriptBrain Res. Author manuscript; available in PMC 2010 January 16. Published in final edited form as:Brain Res. 2009 January 16; 1249: 148-161. doi:10.1016/j.brainres.2008.009. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript IntroductionWorking memory refers to the retention and manipulation of information, typically in a time scale of seconds. There is almost a universal consensus that working memory is critical for a range of cognitive abilities including planning (Prabhakaran et al., 2000) reasoning (De Neys and Verschueren, 2006) lang...

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