Beta-band activity in medial prefrontal cortex predicts source memory encoding and retrieval accuracy

Karuna Subramaniam,Coleman Garrett,Leighton B N Hinkley,Chang Cai,Anne Findlay,Hardik Kothare,John F Houde,Danielle Mizuiri,Srikantan S Nagarajan

doi:10.1038/s41598-019-43291-7

Karuna Subramaniam, Coleman Garrett + Show 7 more

Open Access

https://doi.org/10.1038/s41598-019-43291-7

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Journal: Scientific Reports	Publication Date: May 2, 2019
Citations: 11	License type: open-access

Affiliation: University of California, San Francisco

Abstract

Reality monitoring is defined as the ability to distinguish internally self-generated information from externally-derived information. The medial prefrontal cortex (mPFC) is a key brain region subserving reality monitoring and has been shown to be activated specifically during the retrieval of self-generated information. However, it is unclear if mPFC is activated during the encoding of self-generated information into memory. If so, it is important to understand whether successful retrieval of self-generated information critically depends on enhanced neural activity within mPFC during initial encoding of this self-generated information. We used magnetoencephalographic imaging (MEGI) to determine the timing and location of cortical activity during a reality-monitoring task involving self generated contextual source memory encoding and retrieval. We found both during encoding and retrieval of self-generated information, when compared to externally-derived information, mPFC showed significant task induced oscillatory power modulation in the beta-band. During initial encoding of self-generated information, greater mPFC beta-band power reductions occurred within a time window of −700 ms to −500 ms prior to vocalization. This increased activity in mPFC was not observed during encoding of externally-derived information. Additionally, increased mPFC activity during encoding of self-generated information predicted subsequent retrieval accuracy of this self-generated information. Beta-band activity in mPFC was also observed during the initial retrieval of self-generated information within a time window of 300 to 500 ms following stimulus onset and correlated with accurate retrieval performance of self-generated information. Together, these results further highlight the importance of mPFC in mediating the initial generation and awareness of participants’ internal thoughts.

Highlights

Reality monitoring is defined as the ability to distinguish the source of internally self-generated information from outside reality[1,2,3,4]
The lack of medial prefrontal cortex (mPFC) activity closer to vocalization onset demonstrates that mPFC activity does not appear to mediate a general motor preparation to act. These findings suggest that mPFC was only active within a specific time window prior to this point, which likely represents the initial generation of one’s own internal thoughts, and the cognitive volition to transform these internally-generated thoughts into actions
(i.e., after 500 ms) negates the idea that mPFC activity could be attributed to a general motor preparation to act (Fig. 3). These findings indicate that mPFC activity observed during these specific time windows likely represents the initial generation and awareness of one’s own thoughts and the volition to cognitively prepare to transform these internal thoughts into self-initiated actions

Summary

Introduction

Reality monitoring is defined as the ability to distinguish the source of internally self-generated information from outside reality (externally-derived information)[1,2,3,4]. We use MEG to examine the timing of precisely when induced neural oscillatory activity mediating the initial encoding of self-generated information can predict and facilitate accurate retrieval of this self-generated information. Reconstructions of MEG sensor data using adaptive spatial filtering techniques[9] provide precise source localization during the encoding and retrieval of self-generated information These accurate source localization reconstructions together with the high temporal resolution of MEGI, allow us to capitalize on understanding both the timing and location of neural activity from internal thought generation to preparation and volition to transform these intentions into actions. MEG source analyses enables us to examine the precise timing of activation in mPFC and probe whether mPFC is activated during the initial generation of one’s own thoughts (but not during the externally-derived condition) prior to motor preparation and execution. Support for these hypotheses would indicate that mPFC mediates the successful encoding of self-generated information, and that its activity can predict and facilitate subsequent retrieval and accurate identification of this self-generated information

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