Regional Excitatory-Inhibitory Balance Relates to Self-Reference Effect on Recollection via the Precuneus/Posterior...

Area of Science:

• Cognitive Neuroscience
• Neuroimaging
• Neurochemistry

Background:

• The self-referential effect (SRE) enhances memory and perception, linked to default mode network (DMN) activation.
• Neurochemical underpinnings of DMN activity in SRE remain unclear.
• Excitation/inhibition (E/I) balance is crucial for cognition and may influence SRE.

Purpose of the Study:

• To investigate the association between neurochemical E/I balance and DMN neural processes in self-referential encoding.
• To examine the role of the glutamate/glutamine (Glx) to gamma-aminobutyric acid (GABA) ratio in SRE.

Main Methods:

• Utilized 1H-Magnetic Resonance Spectroscopy (1H-MRS) to measure Glx and GABA concentrations in the precuneus/posterior cingulate cortex (Pcu/PCC).
• Employed functional Magnetic Resonance Imaging (fMRI) during a task involving self-referential and semantic judgments.
• Analyzed task-dependent functional connectivity between Pcu/PCC and medial prefrontal cortex (mPFC).

Main Results:

• Self-related encoding improved memory and increased Pcu/PCC activation compared to semantic encoding.
• Pcu/PCC activation positively correlated with the Glx/GABA+ ratio.
• Pcu/PCC-mPFC connectivity associated with both Glx/GABA+ ratio and SRE memory accuracy, mediated by the Glx/GABA+ ratio.

Conclusions:

• Neurochemical E/I balance, proxied by the Glx/GABA+ ratio, is linked to self-related cognition.
• The Pcu/PCC-mPFC connectivity mediates the relationship between neurochemical balance and SRE memory enhancement.
• Findings highlight the role of E/I balance in DMN function and self-related processes.