RT Journal Article
SR Electronic
T1 Serial representation of items during working memory maintenance at letter-selective cortical sites
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 171660
DO 10.1101/171660
A1 Ali Bahramisharif
A1 Ole Jensen
A1 Joshua Jacobs
A1 John Lisman
YR 2017
UL http://biorxiv.org/content/early/2017/08/02/171660.abstract
AB We used intracranial recordings to study brain oscillations during a working memory task. To analyze sites involved in working memory, we focused on sites at which the elevation of the broadband gamma signal depended on which letter was presented. During the encoding and maintenance periods of the task, gamma and theta power were affected, but in opposing ways. Nevertheless, cross-frequency coupling (CFC) was present during both periods, suggesting that CFC is fundamental to the task. We tested a previously proposed model according to which different items are active at different phases of the theta cycle (in different gamma cycles within the theta cycle). Consistent with this model, the theta phase of letter-induced gamma elevation during maintenance reflected the order of letter presentation. These results suggest that working memory is organized by a theta-gamma code and provide strong support for the serial representation of items held in working memory.