Gianfranco Fortunato¹ (), Valeria Centanino¹, Domenica Bueti¹; ¹International School for Advanced Studies (SISSA)

In the human brain, millisecond durations of visual events are processed across different regions, from early visual to parietal and frontal areas. Previous functional magnetic resonance imaging (fMRI) studies have shown that early visual areas respond to durations via monotonic tuning, while downstream areas employ unimodal tuning. However, whether and how the properties of unimodal tuning change along the hierarchy to mediate duration perception is still unknown. In this study, we recorded brain activity at 7T-fMRI while participants performed a duration discrimination task of visual stimuli. We modeled BOLD responses using the population receptive field approach for estimating vertex-wise tuning functions. Results showed that neuronal populations in occipital visual areas maximally respond to long durations, in line with the presence of monotonic tuning mediating duration encoding. In parietal, premotor and caudal supplementary motor areas, neuronal populations show selectivity to different durations, covering the entire presented range, and they are also spatially organized in maps. Both properties are compatible with the read-out of temporal information. In rostral supplementary motor areas, inferior frontal cortex and anterior insula, neuronal populations selectively respond to the mean of the presented durations. This selectivity also correlates with participants' point of subjective equality, suggesting a subjective representation of temporal information used to solve the task. Finally, our results showed the existence of specific dependencies between these neuronal populations, likely supporting the presence of distinct functional stages in duration processing and perception i.e., encoding, representation and task-related decisions. Overall, our findings suggest the existence of a putative functional hierarchy of visual temporal processing and highlight the role of tuning properties as neural mechanism of duration perception.