Behavioral and Brain Functions

Background: Dorsolateral prefrontal cortex (DLPFC), posterior parietal cortex, and regions in the occipital cortex have been identified as neural sites for visual working memory (WM). The exact involvement of the DLPFC in verbal and non-verbal working memory processes, and how these processes depend on the time-span for retention, remains disputed. Methods: We used functional MRI to explore the neural correlates of the delayed discrimination of Gabor stimuli differing in orientation. Twelve subjects were instructed to code the relative orientation either verbally or non-verbally with memory delays of short (2 s) or long (8 s) duration. Results: Blood-oxygen level dependent (BOLD) 3-Tesla fMRI revealed significantly more activity for the short verbal condition compared to the short non-verbal condition in bilateral superior temporal gyrus, insula and supramarginal gyrus. Activity in the long verbal condition was greater than in the long non-verbal condition in left language-associated areas (STG) and bilateral posterior parietal areas, including precuneus. Interestingly, right DLPFC and bilateral superior frontal gyrus was more active in the non-verbal long delay condition than in the long verbal condition. Conclusion: The results point to a dissociation between the cortical sites involved in verbal and non-verbal WM for long and short delays. Right DLPFC seems to be engaged in non-verbal WM tasks especially for long delays. Furthermore, the results indicate that even slightly different memory maintenance intervals engage largely differing networks and that this novel finding may explain differing results in previous verbal/non-verbal WM studies. Background Working Memory (WM) is the ability to keep a limited amount of information online for immediate use during short intervals [1]. In typical WM experiments 1 to 10 items are maintained in memory for periods up to and including 60 s [2]. The classical model of WM consists of the central executive and three subsidiary systems, namely the visuo-spatial sketchpad, the phonological loop, and the recently proposed episodic buffer [3]. Published: 25 October 2007 Behavioral and Brain Functions 2007, 3:56 doi:10.1186/1744-9081-3-56 Received: 4 September 2007 Accepted: 25 October 2007 This article is available from: http://www.behavioralandbrainfunctions.com/content/3/1/56 © 2007 Rothmayr et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.