Research Report Age-related reorganization of encoding networks directly influences subsequent recognition memory Danielle J. Tisserand a, * , Anthony R. McIntosh a , Freddy M. van der Veen b , Walter H. Backes c , Jelle Jolles d a Rotman Research Institute, Baycrest Centre for Geriatric Care, 3560 Bathurst Street, Toronto, Ontario, Canada M6A 2E1 b Department of Psychiatry, Erasmus Medical Centre, Rotterdam, The Netherlands c Department of Radiology, Maastricht University Hospital, Maastricht, The Netherlands d Brain and Behaviour Institute, Maastricht University, Maastricht, The Netherlands Accepted 9 April 2005 Available online 13 June 2005 Abstract Functional magnetic resonance imaging was used to link performance-related brain activity during two word encoding tasks to subsequent recognition for those words in young and older adults. There were no significant group differences in performance during encoding, but the young subjects performed better than the older at the recognition task. Performance-related brain networks strongly differed between the two groups. In young subjects, there were two networks associated with performance, one related to encoding (mainly involving premotor and parietal brain regions) and the other to recognition (involving middle frontal, and lateral and medial temporal regions), whereas the network for older subjects (including prefrontal, premotor, lateral and medial temporal regions) was associated both with encoding and recognition. Areas in this network strongly overlapped with those supporting recognition in the young subjects (e.g., medial temporal lobe), suggesting that older subjects may have recruited these areas to maintain performance during encoding. However, this reorganization of brain networks appears to have come at the cost of subsequent recognition. D 2005 Elsevier B.V. All rights reserved. Theme: Neural basis of behavior Topic: Aging Keywords: Functional magnetic resonance imaging; Human; Memory; Medial temporal lobe; Prefrontal cortex 1. Introduction There is growing evidence that age-related changes in cognitive performance are accompanied by a functional reorganization of the brain areas involved in these processes [7,13,24]. For example, Della-Maggiore et al. [13] and Grady et al. [24] found that, despite similar task-related engagement of the hippocampus in young and older adults, there was a large difference between the groups in the brain regions functionally connected to it. Such a reorganization of neural networks may reflect the natural course of aging, with a negative impact upon cognitive operations. In other cases, it may represent the creation of new functional networks in an attempt to compensate for a decline in efficiency of existing ones [17]. However, compensatory changes to preserve function in one cognitive operation may come at a cost of performance at another. For instance, older adults may make an extra effort to maintain adequate performance levels, but this attempt might be insufficient when task demands are high [1]. From the cognitive aging literature, it is known that older individuals are less likely to spontaneously use encoding strategies than young [11]. However, these age effects are attenuated when contextual support is provided. That is, when subjects are given cues about how to efficiently process 0926-6410/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.cogbrainres.2005.04.016 * Corresponding author. Fax: +1 416 7852862. E-mail address: dtisserand@rotman-baycrest.on.ca (D.J. Tisserand). URL: http://www.rotman-baycrest.on.ca/tisserand (D.J. Tisserand). Cognitive Brain Research 25 (2005) 8 – 18 www.elsevier.com/locate/cogbrainres