Task Relevance Enhances Early Transient and Late Slow-Wave Activity of Distributed Cortical Sources |
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Authors: | CJ Aine JM Stephen R Christner D Hudson E Best |
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Institution: | (1) Research Service, New Mexico VA Health Care System, Albuquerque, New Mexico;(2) 1501 San Pedro SE, Bldg 14 (151), Albuquerque, NM 87108, USA;(3) Departments of Radiology, Neurology and Neuroscience, UNM School of Medicine, Albuquerque, NM 87131, USA;(4) The MIND Institute, 801 University Blvd SE, Suite 200, Albuquerque, NM 87106, USA;(5) Biomedical Research Institute of New Mexico (BRINM), 1501 San Pedro SE, Bldg 14 (151), Albuquerque, NM 87108, USA;(6) Biophysics Group, Physics Division, Los Alamos National Laboratory, MS D454, Los Alamos, NM 87545, USA |
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Abstract: | The primary purpose of these studies was to link together concepts related to attention/working memory and feedforward/feedback activity using MEG response profiles obtained in humans. Similar to recent studies of attention in monkeys, we show early spike-like activity (<200 ms poststimulus), most likely reflecting an early transient excitatory response mixed with feedback influences, followed by slow-wave activity (>200 ms poststimulus) in MEG cortical response profiles evoked by a visual working memory task. We experimentally dissociated the early transient activity from the later sustained activity (predominately feedback) by conducting an auditory size classification task. Words, representing common objects, evoked activity in occipital cortex (presumably due to imagery) even though visual stimuli were not present in this task. The initial spike was absent from the response profile obtained from occipital cortex, leaving only slow-wave activity, thereby allowing us to characterize or profile feedback activity in this situation. Attention or task relevance enhanced the initial spike and slow-wave activity in visually responsive areas. Prefrontal activity, along the superior frontal sulcus, evoked by the working memory task, was active later in time than initial activity in visual cortex and later than the earliest effect of attention modulation in visual cortex. |
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Keywords: | working memory magnetoencephalography MEG feedforward/feedback transient/sustained attention cross-correlation |
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