Isolating the Contribution of the Koniocellular Visual Pathway in Aversive Learning in Human Visual Cortex

The present study examined how the koniocellular retino-geniculate visual pathway contributes to the electrocortical amplification of threat cues in human visual cortex using a simple aversive conditioning task. The task involved S-cone isolating stimuli (Tritan condition) and achromatic luminance stimuli (luminance condition) that preferentially activated the koniocellular pathway and luminance channels, respectively. Steady-state visual evoked potential (ssVEPs) responses to the conditioned threat cues (CS+) and safety cues (CS-) in each condition were analyzed using a non-parametric Bayesian bootstrapped approach. The Tritan and luminance conditions exhibited greater ssVEP responses to the CS+ stimuli compared to the CS-stimuli in occipital sensors early into the trial (0 ms - 1000 ms; logBF10 > 2). In addition to these early conditioning effects, a late conditioning effect was observed (1500 ms - 2500 ms) in the Tritan condition that emerged over bilateral anterior sensors (logBF10 > 2). To further examine the koniocellular contribution to aversive learning, transitive Bayes factors were computed to compare the magnitude of the conditioning effects across conditions. Transitive Bayesian comparisons showed that the early conditioning effect was larger for the luminance condition than for the Tritan condition (logBF10 > 2). Furthermore, the late conditioning effect remained larger in the Tritan condition compared to the luminance condition (logBF10 > 2). Our results are consistent with previous work demonstrating that Tritan stimuli elicit enhanced electrocortical responses and with theoretical notions suggesting that the koniocellular pathway contributes to the representation of threat signals in human visual cortex.