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Activity in human medial temporal lobe associated with encoding process in spatial working memory revealed by magnetoencephalography

Authors

  • Pablo Campo,

    1. Centro de Magnetoencefalografía Dr Pérez-Modrego, Pabellón 8, Facultad de Medicina, Universidad Complutense de Madrid, 28040, Madrid, Spain
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  • Fernando Maestú,

    1. Centro de Magnetoencefalografía Dr Pérez-Modrego, Pabellón 8, Facultad de Medicina, Universidad Complutense de Madrid, 28040, Madrid, Spain
    2. Departamento de Psicología Básica II (Procesos Cognitivos), Facultad de Psicología, Universidad Complutense de Madrid, Madrid, Spain
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  • Almudena Capilla,

    1. Centro de Magnetoencefalografía Dr Pérez-Modrego, Pabellón 8, Facultad de Medicina, Universidad Complutense de Madrid, 28040, Madrid, Spain
    2. Departamento de Psicología Básica II (Procesos Cognitivos), Facultad de Psicología, Universidad Complutense de Madrid, Madrid, Spain
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  • Santiago Fernández,

    1. Departamento de Psicología, Universidad Camilo José Cela, Madrid, Spain
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  • Alberto Fernández,

    1. Centro de Magnetoencefalografía Dr Pérez-Modrego, Pabellón 8, Facultad de Medicina, Universidad Complutense de Madrid, 28040, Madrid, Spain
    2. Departamento de Psiquiatría, Facultad de Medicina, Universidad Complutense de Madrid, Spain
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  • Tomás Ortiz

    1. Centro de Magnetoencefalografía Dr Pérez-Modrego, Pabellón 8, Facultad de Medicina, Universidad Complutense de Madrid, 28040, Madrid, Spain
    2. Departamento de Psiquiatría, Facultad de Medicina, Universidad Complutense de Madrid, Spain
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Dr Tomás Ortiz, 1Centro de Magnetoencefalografía Dr Pérez-Modrego, as above.
E-mail: cmeg@rect.ucm.es

Abstract

Animal studies have suggested that working memory may be affected after lesions in the medial temporal lobe, although this assumption has not been corroborated by neuropsychological studies in humans. However, very recently, several functional neuroimaging studies in humans have successfully observed activation of the medial temporal lobe during working memory tasks. The main aim of this study was to investigate the contribution of the medial temporal lobe to the encoding process in spatial working memory. To address this issue we registered the neuromagnetic brain patterns of eight adult volunteers while they performed a spatial working memory task and more perceptual task using identical stimuli. After a initial phase (between 200 and 400 ms) without differences in activation, the medial temporal lobe showed a sustained activity, more evident in the right hemisphere, lasting up to 800 ms during the encoding stage of the spatial working memory task, while the activation in the perceptual task terminated earlier (∼400 ms after stimulus onset). The finding of a continued activation of the medial temporal lobe strongly suggests the contribution of this brain region to encoding operations in working memory.

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