Cerebral Cortex Advance Access originally published online on August 3, 2005
Cerebral Cortex 2006 16(5):609-617; doi:10.1093/cercor/bhj007
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Increased Neural Efficiency with Repeated Performance of a Working Memory Task is Information-type Dependent
1 Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD 21218, USA, 2 Department of Neurobiology, Stanford University, Stanford, CA 94305, USA, 3 Department of Psychology, Stanford University, Stanford, CA 94305, USA, 4 Department of Neuroscience, Johns Hopkins University, Baltimore, MD 21218, USA and 5 F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD 21205, USA
Address correspondence to Susan Courtney, Department of Psychological and Brain Sciences, Ames Hall, 3400 N. Charles Street, Baltimore, MD 21218, USA. Email: courtney{at}jhu.edu.
Unlike tasks in which practice leads to an automatic stimulus–response association, it is thought working memory (WM) tasks continue to require cognitive control processes after repeated performance. Previous studies investigating WM task repetition are in accord with this. However, it is unclear whether changes in neural activity after repetition imply alterations in general control processes common to all WM tasks or are specific to the selection, encoding and maintenance of the relevant information. In the present study, functional magnetic resonance imaging (fMRI) was used to examine changes during sample, delay and test periods during repetition of both object and spatial delayed recognition tasks. We found decreases in fMRI activation in both spatial and object-selective areas after spatial WM task repetition, independent of behavioral performance. Few areas showed changed activity after object WM task repetition. These results indicate that spatial task repetition leads to increased efficiency of maintaining task-relevant information and improved ability to filter out task-irrelevant information. The specificity of this repetition effect to the spatial task suggests a difference exists in the nature of the representation of object and spatial information and that their maintenance in WM is likely subserved by different neural systems.
Key Words: fMRI • object working memory • prefrontal cortex • spatial working memory • task repetition
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