To assess color expectations with high spatio-temporal resolution, I first set up simultaneous EEG/MEG (electro- and magnetoencephalography) recordings, and adjusted colors in the DKL-space to make sure that they match in luminance and saturation, such that any effect observed can in the end be unambiguously linked to color hue. I collected full EEG/MEG datasets (n=37) for decoding color from the brain and testing whether color representations emerge in periods of color anticipation. As a first step, to reconstruct color representations from brain activity, we employed a color localizer task, where human participants were shown four different colors while their electromagnetic brain responses were recorded (Figure 1, A1). Using multivariate pattern analyses, we found color-related information in activity patterns peaking around 120ms after color presentation onset in early visual regions (Figure 1, A2). As a second step, participants then viewed colored stimuli presented in an 80% predictable sequence, enabling the brain to form expectations about the upcoming color (see Figure 1, B1 for an example sequence). A neutral grey placeholder was shown 400ms before the actual color stimulus to evoke a measurable visual response during color expectations (“ping approach”). A decoding model trained on the color localizer data could successfully reconstruct not only the color from the post-stimulus response (Figure 1, B2, lower row) but also from the brain activity elicited by the grey placeholder (Figure 1, B2, upper row). Our findings demonstrate that human predictions carry, indeed, decodable sensory color information in early visual cortical areas. This further specifies the level of sensory detail that is present in predictive sensory templates. Understanding what sensory information is actually contained in human expectations and at which level of detail they operate will also help to better link prediction processes to perception and attentional guidance.
The results have been presented on national and international conferences and are currently written up for open-access publication. A new study leveraging color decoding techniques and applying it to a follow-up research question is currently running under my supervision.
