Developmental Aspects and Neurobiological Correlates of Working and Associative Memory

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Gerald Goldstein Daniel N. Allen

VA Pittsburgh Healthcare System, Pittsburgh, Pennsylvania University of Nevada Las Vegas

Nicholas S. Thaler James F. Luther

University of Oklahoma Health Sciences VA VISN IV Mental Illness Research, Educational, and Clinical

Center, VA Pittsburgh Healthcare System, Pittsburgh,

Pennsylvania

Kanagasabai Panchalingam and Jay W. Pettegrew

University of Pittsburgh School of Medicine

Objective: It has been shown that verbal working and associative memory have different developmental trajectories with working memory, taking a linear course from early childhood to adolescence, whereas associative memory takes a curvilinear course asymptoting at about age 12. This study made a determination of whether these trajectories tracked with 2 magnetic resonance spectroscopy imaging (MRSI) variables: phosphocreatine level (PCr) and gray matter percentage (GM%). Method: In a cross-sectional study, 94 children ranging in age from 6–14 years were administered tests of verbal working and associative memory and underwent an MRSI procedure evaluating 6 major brain regions. The study considered PCr levels and GM% in the 6 regions. Loess curves were constructed plotting the memory tests and MRSI variables across age, and trajectories were evaluated. Results: PCr showed a linear increase with age, particularly in the left superior temporal lobe with this increase closely tracking improvement in working memory but not associative memory scores. GM% did not increase with age in any brain region, and there was no tracking with either of the memory tests. Conclusion: Verbal working memory and verbal associative memory have differing age trajectories, with working memory showing close tracking with PCr level, mainly in the left superior temporal lobe. No such tracking was found for the associative memory tests. GM% curves were flat across regions, showing no association with age.

Keywords: working memory, MR spectroscopy, Loess curves

Working memory is a limited capacity memory system that provides temporary storage to manipulate information for complex cognitive tasks, such as those involved in learning and reasoning (Baddeley & Hitch, 1974). The distinction has been made between verbal and other forms of working memory such as spatial working memory, and different measures are used to evaluate these abilities separately. This study is concerned with verbal working memory, which has been operationally defined by both psychometric tests and experimental procedures that assess it in various ways. For

Gerald Goldstein, VISN IV Mental Illness Research, Educational, and Clinical Center, VA Pittsburgh Healthcare System, Pittsburgh, PA; Daniel N. Allen, Department of Psychology, University of Nevada Las Vegas; Nicholas S. Thaler, Department of Psychiatry and Behavioral Sciences, University of Oklahoma Health Sciences; now at UCLA Semel Institute for Neuroscience and Human Behavior, Department of Psychiatry and Behavioral Sciences James F. Luther, VISN IV Mental Illness Research, Educational, and Clinical Center, VA Pittsburgh Healthcare System, Pittsburgh, PA; Kanagasabai Panchalingam, Department of Psychiatry, University of

Pittsburgh School of Medicine; Jay W. Pettegrew, Department of Psychi1

example, IQ and memory batteries often incorporate working memory indices for clinical use (Sheslow & Adams, 2003; Wechsler, 2008, 2009), whereas laboratory procedures such as the n-back and Sentence Memory Test are also available (Daneman & Carpenter, 1980; Jaeggi et al., 2010). Typically, verbal working memory tests use auditory stimuli as test items, as is the case in this study. Although this form of memory is generally characterized as verbal working memory, it is usually evaluated with spoken language material. Its definition, first proposed by Baddeley (1992,

atry, Department of Neurology, Department of Behavioral and Community Health Services, University of Pittsburgh School of Medicine and Department of Bioengineering, University of Pittsburgh.

This work was supported in part by an NIHCD/NIH HD-39799 grant (JWP) Indebtedness is expressed to the Medical Research Service and the VA VISN-IV Mental Illness Research, Education and Clinical Center (MIRECC) Depertment of Veterans Affairs.

Correspondence concerning this article should be addressed to Jay W. Pettegrew, Department of Psychiatry, University of Pittsburgh School of Medicine, RIDC Park, 2600 Kappa Drive, Pittsburgh PA 15238. E-mail:

pettegrew@phfrinc.com

2003), is the ability to maintain and manipulate a limited amount of information over a period of time, generally while solving a problem. Associative memory is defined as the process of storage and retrieval of information beyond the initial few seconds. Working memories disappear after that time interval while associative memories are stored in the long-term memory system.