WHOLE-BRAIN REACTIVATION OF VISUALLY EVOKED PATTERNS AT REST

This study investigates the relation between spontaneous and task-evoked brain activity patterns (AP). Evoked-AP have been reported to be “reactivated” at rest in stimulus-specific processing areas. If reactivations at rest represent information states working as “priors” to anticipate upcoming activities (Pezzulo, Trends Cogn Sci., 2021), the patterns shouldn’t be confined to specialized areas, but be widely present across cortex. To evaluate this hypothesis, we re-analysed Kim’s dataset (Kim, J Neurophysiol. 2020) searching for reactivation of evoked patterns beyond visual areas. Sixteen participants underwent fMRI both at rest and while looking at different categories of visual stimuli (task) (Fig.1a). A GLM determined participant- and category-specific whole-brain task-APs. These were correlated for each vertex with the rest-AP at each time point, resulting in an evoked-AP-to-rest correlation timeseries. The 90^th percentile (U90) of the correlation values distribution measures the degree to which each evoked AP is reactivated at rest (Fig.1b). The resulting U90-maps show both category-specific areas and a common backbone of regions reactivating all visual stimuli, prominently in primary visual and dorsal parietal cortex (Fig.1c). Category specificity was highlighted in deltaU90-maps (“reactivation maps”) revealing preferential reactivation not only in classic category-selective visual areas but also in parietal and prefrontal regions. Category-specific reactivation maps aligned best with the corresponding category evoked-AP, although reactivation extended more broadly (Fig.1d). Even if preliminary, these results support one of the “priors” theory predictions, showing visual stimuli reactivation in a distributed set of regions beyond stimulus-specific areas, and confirming the task-rest pattern similarity.