Yiming Jin¹ (), Nan Jin^1,2, Yongchun Cai¹; ¹Zhejiang University, ²Ludwig-Maximilians-Universität München

The aperiodic exponent (spectral slope) of the neural power spectrum has recently emerged as a putative non-invasive marker for cortical excitation/inhibition (E/I) balance. While this metric reflects the global state of cortical circuitry, it remains unclear whether intrinsic resting-state E/I balance constrains specific, localized sensory computations. Here, we investigated whether resting-state EEG 1/f slopes predict the strength of Visual Surround Suppression (VSS), a canonical inhibitory mechanism in the visual cortex wherein neural responses to stimuli within the classical receptive field (CRF) are suppressed by stimulation of the extra-classical surround. We recorded resting-state EEG from 25 healthy adults and extracted 1/f slopes from the occipital cortex using spectral parameterization (i.e., FOOOF). We then measured VSS strength for each participant using three independent paradigms to ensure construct validity: (1) a contrast matching task (measuring the suppression of apparent contrast by a surrounding grating); (2) a motion discrimination task (measuring the effect of stimulus size on duration thresholds, indexing spatial suppression); and (3) an SSVEP paradigm (measuring the modulation of signal-to-noise ratio in steady-state responses to a central flicker by a static surround). At the group level, all three paradigms yielded robust surround suppression effects, confirming the validity of our measurements. However, correlation analyses revealed no significant relationship between resting-state occipital 1/f slopes and any behavioral or neural measures of VSS strength across individuals. These findings suggest that while the 1/f slope may index global cortical E/I tone, visual surround suppression relies heavily on local circuit dynamics (such as divisive normalization) that operate independently of the baseline cortical state. Our results imply a mechanistic dissociation between global resting-state E/I balance and the local inhibitory computations governing sensory processing.