Abstract
Dorsolateral prefrontal cortex (DLPFC) is thought to organize items in working memory and this organizational role may also influence long-term memory. To causally test this hypothesized role of DLPFC in long-term memory formation, we used theta-burst noninvasive stimulation (TBS) to modulate DLPFC involvement in a memory task that assessed the influence of active short-term retrieval on later memory. Human subjects viewed three objects on a grid and then either actively retrieved or passively restudied one object’s location after a brief delay. Long-term memory for the other objects was assessed after a delay to evaluate the beneficial role of active short-term retrieval on subsequent memory for the entire set of object-locations. We found that DLPFC TBS had no significant effects on short-term memory. In contrast, DLPFC TBS impaired long-term memory selectively in the active-retrieval condition, but not in the passive-restudy condition. These findings are consistent with the hypothesized contribution of DLPFC to the organizational processes operative during active short-term retrieval that influence long-term memory, although other regions that were not stimulated could provide similar contributions. Notably, active-retrieval and passive-restudy conditions were intermixed, and therefore nonspecific influences of stimulation were well controlled. These results suggest that DLPFC is causally involved in organizing event information during active retrieval to support coherent long-term memory formation.
Significance Statement Although dorsolateral prefrontal cortex (DLPFC) has been implicated in short-term working memory organization, its long-term memory contributions have not been established. Building on fMRI findings, we tested the role of DLPFC in organizing event information during memory formation to support long-term episodic memory. Our task involved both active-retrieval and passive-restudy encoding conditions, which varied the extent to which event elements were organized around select information. Modulation of DLPFC via theta burst noninvasive stimulation (TBS) selectively altered long-term memory formation in the active-retrieval condition, but not the passive-restudy condition. These results pinpoint the role of DLPFC in organizing event information to form coherent long-term memories and demonstrate that TBS can be used to disentangle cognitive processes that contribute to long-term memory.
Footnotes
Authors declare no conflict of interest.
This research was supported by grants R21MH108863 from the National Institute of Mental Health and F32NS087885 from the National Institute of Neurological Disorders and Stroke. The content is solely the responsibility of the authors and does necessarily represent the official view of the National Institutes of Health. Neuroimaging was performed at the Northwestern University Center for Translational Imaging, supported by Northwestern University Department of Radiology. R21MH108863 from the National Institute of Mental Health and F32NS087885 from the National Institute of Neurological Disorders and Stroke.
This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license, which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed.
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