Glutamate in Salience Network Predicts BOLD Response in Default Mode Network During Salience Processing.

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Neuroimaging

Background:

• The salience network (SN), including the dorsal anterior cingulate cortex (dACC) and anterior insula (AI), is crucial for processing salient information.
• Previous magnetic resonance spectroscopy (MRS) studies link glutamate concentration in the anterior cingulate cortex (ACC) to attentional scope.
• The role of dACC glutamate in modulating brain responses to salience processing remains to be fully elucidated.

Purpose of the Study:

• To investigate whether glutamate concentration in the dACC influences brain activity during salience processing.
• To examine the relationship between dACC glutamate levels and the brain's response to emotional and unexpected stimuli.

Main Methods:

• Utilized 7-Tesla STEAM MRS to measure glutamate concentrations in the dACC of 27 healthy subjects.
• Employed functional magnetic resonance imaging (fMRI) to assess brain responses during a salience processing task involving emotional and unexpected stimuli.
• Performed regression analyses to correlate MRS and fMRI data, controlling for demographic and anatomical factors.

Main Results:

• Stimulus salience, driven by sexual content and unexpectedness, attenuated deactivation in the posterior cingulate cortex (PCC).
• Higher glutamate levels in the dACC were associated with this attenuated PCC deactivation.
• A significant correlation was found between dACC glutamate concentration and brain activity during salience processing.

Conclusions:

• Glutamate concentration in the dACC plays a key role in modulating brain responses to salience.
• The dACC's glutamate levels help balance the deactivation in the PCC in response to inherent stimulus salience.
• Findings provide insights into the neurochemical underpinnings of attention and salience processing.