Abstract
The current work investigated adaptive visuocortical changes in spatial frequency tuning using electrophysiology and a classical fear conditioning paradigm in which the spatial frequency of Gabor gratings differentially predicted a noxious sound. Fifty-five undergraduate students (MAGE = 18.69, SDAGE = 0.91, 36 female) at the University of Florida participated in the study. High-density (128 channel) EEG was continuously recorded while participants viewed 400 total trials of individually presented Gabor patches of 10 different spatial frequencies (40 total trials per frequency). Gabor stimuli were flickered to produce sweep steady-state visual evoked potentials (ssVEPs) with a temporal frequency of 13.33 Hz. Stimulus contrast was ramped up from 0 to 100% Michelson over the course of each trial. In the second half of the experimental session, a selected range of Gabor stimuli (either with the lowest or highest spatial frequencies, manipulated between-participants) were paired with an aversive 90 dB white noise auditory stimulus. The amplitude envelope of the sweep ssVEP response at 13.33 Hz was extracted via Hilbert transformation and Alpha band (7.93 – 12.07 Hz) activity was isolated through wavelet transform, with differences between paired and unpaired gratings before and after conditioning evaluated statistically using permutation-controlled mass-univariate t-tests. Ongoing analyses indicate that amplitude reduction in the alpha band (alpha blocking) was more pronounced when viewing spatial frequencies paired with aversive stimuli, compared with when viewing non-paired Gabors. Notably, alpha blocking did not follow the contrast increase across the trial, but the Hilbert envelope of the sweep-ssVEP did, suggesting that alpha reflects a detection/attention mechanism rather than a contrast-tracking mechanism. Results suggest that higher-order attention network responses to fear-conditioned stimuli may operate independently of low-level stimulus feature processing in primary visual cortex as indexed by ssVEPs.