Theta Oscillations in Human Cortex During a Working-Memory Task: Evidence for Local Generators

1 Volen Center for Complex Systems, Brandeis University, Waltham; 2 Department of Neurosurgery, Children's Hospital and 3 Department of Neurology, Brigham and Women's Hospital, Boston, Massachusetts; and 4 Department of Psychology, University of Pennsylvania, Philadelphia, Pennsylvania Sub...

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Published in:Journal of neurophysiology 2006-03, Vol.95 (3), p.1630-1638
Main Authors: Raghavachari, S, Lisman, J. E, Tully, M, Madsen, J. R, Bromfield, E. B, Kahana, M. J
Format: Article
Language:English
Subjects:
Adolescent
Adult
Biological Clocks - physiology
Brain Mapping - methods
Cerebral Cortex - physiology
Female
Humans
Male
Memory, Short-Term - physiology
Neural Pathways - physiology
Psychomotor Performance - physiology
Theta Rhythm - methods
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Summary:1 Volen Center for Complex Systems, Brandeis University, Waltham; 2 Department of Neurosurgery, Children's Hospital and 3 Department of Neurology, Brigham and Women's Hospital, Boston, Massachusetts; and 4 Department of Psychology, University of Pennsylvania, Philadelphia, Pennsylvania Submitted 20 April 2005; accepted in final form 28 September 2005 Cortical theta appears important in sensory processing and memory. Intracanial electrode recordings provide a high spatial resolution method for studying such oscillations during cognitive tasks. Recent work revealed sites at which oscillations in the theta range (4–12 Hz) could be gated by a working-memory task: theta power was increased at task onset and continued until task offset. Using a large data set that has now been collected (10 participants/619 recording sites), we have sufficient sampling to determine how these gated sites are distributed in the cortex and how they are synchronized. A substantial fraction of sites in occipital/parietal (45/157) and temporal (23/280) cortices were gated by the task. Surprisingly, this aspect of working-memory function was virtually absent in frontal cortex (2/182). Coherence measures were used to analyze the synchronization of oscillations. We suspected that because of their coordinate regulation by the working-memory task, gated sites would have synchronized theta oscillations. We found that, whereas nearby gated sites (
ISSN:0022-3077
1522-1598
DOI:10.1152/jn.00409.2005