Examining excitation-inhibition modulation during social processing using functional magnetic resonance spectroscopy

Area of Science:

• Neuroscience
• Neuroimaging
• Biochemistry

Background:

• Imbalances in brain excitation-inhibition are linked to social communication deficits in neurodevelopmental and psychiatric disorders.
• Functional magnetic resonance spectroscopy (fMRS) enables non-invasive measurement of dynamic neurometabolite changes (glutamate and GABA).

Purpose of the Study:

• To investigate if social stimuli modulate excitatory (glutamate) or inhibitory (GABA) neurometabolites in the human brain.
• To determine if such neurometabolite modulation relates to individual differences in social function.

Main Methods:

• Forty neurotypical adults underwent 3T MRI with fMRS using a J-difference edited sequence.
• GABA+ and Glx (glutamate+glutamine) were quantified in the superior temporal/temporoparietal junction (STG/TPJ) and occipital cortex.
• Participants were exposed to resting state, social video clips, and a checkerboard stimulus, with social function assessed via SRS-2.

Main Results:

• No significant differences in GABA+ or Glx were found between resting and functional conditions (social or checkerboard).
• Bayesian analyses suggested decreased STG/TPJ GABA+ and increased occipital Glx during checkerboard stimulus compared to rest.
• Higher resting Glx in the STG/TPJ was associated with higher social responsiveness scores (SRS-2), but functional metabolite levels were not.
• Sliding time-window analysis revealed reduced Glx in the social brain during social stimulation.

Conclusions:

• Dynamic neurometabolite shifts in response to social stimuli were minimal in neurotypical adults.
• Resting glutamate levels in social brain regions may be associated with social function.
• Future research should employ more challenging social stimuli and explore alternative social brain regions.