Theta oscillations in human cortex during a working-memory task: evidence for local generators.


Journal Article

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 (<20 mm) were often but not always coherent, distant gated sites were almost never coherent. Our results imply that there are local mechanisms for the generation of cortical theta.

Full Text

Cited Authors

  • Raghavachari, S; Lisman, JE; Tully, M; Madsen, JR; Bromfield, EB; Kahana, MJ

Published Date

  • March 2006

Published In

Volume / Issue

  • 95 / 3

Start / End Page

  • 1630 - 1638

PubMed ID

  • 16207788

Pubmed Central ID

  • 16207788

Electronic International Standard Serial Number (EISSN)

  • 1522-1598

International Standard Serial Number (ISSN)

  • 0022-3077

Digital Object Identifier (DOI)

  • 10.1152/jn.00409.2005


  • eng