Parrella, N.-F. | Search bioRxiv

bioRxiv2025

Examining excitation-inhibition modulation during social processing using functional Magnetic Resonance Spectroscopy

An imbalance of brain excitation-inhibition has been implicated in social communication function across neurodevelopmental and psychiatric conditions. Recent advances in functional magnetic resonance spectroscopy (fMRS) allow non-invasive measurement of dynamic changes in excitation-inhibition neurometabolites (glutamate and GABA), revealing potential links with cognitive processes. This study used functional MRS (fMRS) to investigate whether socially-laden stimuli modulate excitatory or inhibitory neurometabolites, and whether modulation relates to social function. Forty neurotypical adults (18-40 years; 20 male) underwent 3T MRI, with fMRS data acquired using a J-difference edited MRS sequence. GABA+macromolecules (GABA+) and glutamate+glutamine (Glx) were quantified in a right social brain region (superior temporal/temporoparietal junction [STG/TPJ]) and a control region (occipital cortex). Participants viewed a fixation cross (traditional resting state MRS; 5 min), silent video clips of social interaction, and a flashing checkerboard as control stimulus (5 min each; counterbalanced). The Social Responsiveness Scale (SRS-2) assessed social function. Block analysis showed no significant differences between resting and functional (social or checkerboard) GABA+ or Glx levels (ps<.05), although Bayesian analyses showed evidence for decreased STG/TPJ GABA+ and increased occipital cortex Glx for checkerboard compared to rest. Higher SRS-2 scores were associated with higher resting STG/TPJ Glx but not GABA+, and functional metabolite levels were not associated with SRS-2 scores (ps>.1). Sliding time- window analyses showed significantly reduced Glx in social brain during social stimulation. Despite sound data collection and analysis techniques, shifts in Glx and GABA+ following social stimuli were minimal. Future research could utilise more challenging social stimuli and examine alternate social brain regions.

neuroscience↗

bioRxiv2023

Resting state aperiodic slope predicts Research Domain Criteria Social Processes in young typically developing adults

The aperiodic exponent of the electrophysiological signal has been utilised to demonstrate differences in brain excitation-inhibition in ageing, cognition, and neuro- and psycho-pathology. Furthermore, excitation-inhibition imbalance has been associated with social communication difficulties in clinical and non-clinical cohorts. No work to date, however, has explored the association between aperiodic activity and social communication difficulties. A total of 40 neurotypical young adults aged 18-24 (24 female; age mean = 21.6, SD = 1.9) each underwent 5 minutes of eyes open and eyes closed resting state electroencephalography using a 64-channel HydroCel Geodesic Sensor Net. Participants also completed Research Domain Criteria social processes measures: Social Responsiveness Scale, Reading the Mind in the Eyes task, and Penn Emotional Recognition Task. Sex differences in aperiodic exponent and offset were observed, with larger exponent and greater offset observed in males, suggestive of greater inhibitory tone. Whole-brain, as well as left and right social brain, aperiodic exponent were moderately correlated with Social Responsiveness Scale Social Communication Index, but not Reading the Mind in the Eyes or Penn Emotional Recognition tasks. However, the correlations between aperiodic exponent and Social Responsiveness Scale Social Communication Index did not survive multiple comparisons correction, and regression models demonstrated that neither aperiodic exponent or offset were significantly predictive of social processes outcomes. These preliminary data provide some evidence that increased aperiodic activity may be associated with social communication difficulties, however, larger samples are needed to validate these initial findings.

neuroscience↗