Abstract
Both functional MRI and neurophysiological evidence suggest that attention serves to shift cortical representations toward behaviorally relevant stimuli (Cukur et al., 2013; David et al., 2008). Attention therefore likely alters the degree to which brain areas share functional representations and form functional brain networks. However, little is known about how attention reconfigures the brain areas involved in such networks (i.e., the network’s cortical extent) to optimize processing of the attended stimuli. To investigate this issue, we reanalyzed a previously published fMRI dataset in which six participants either watched natural movie clips passively or searched for specific object categories (Cukur et al., 2013). To probe how attention influences the cortical extent of functional networks, a new method called model connectivity (MC) was used to recover networks with distinct object category representations (Meschke et al., 2022). While functional connectivity uses BOLD time series to quantify functional coupling, MC uses encoding model weights to quantify the degree to which brain areas share functional representations. Before performing MC, visual-semantic encoding models were constructed separately for the passive viewing and search conditions. Then, MC was applied to the semantic model weights estimated during passive viewing, recovering 18 distinct visual-semantic networks. MC was then used to recover visual-semantic networks from model weights estimated during search, and the brain areas spanned by each network during passive viewing were compared to those recovered during search. While the cortical extent of each network was largely consistent across the attentional conditions, selective attention during search shifted representations towards the attended category, changing the degree to which brain areas shared functional representations. Consequently, brain areas were recruited, dropped, and shifted within visual-semantic networks during search. These results suggest that because attention expands the cortical representations of the attended stimuli, attention also changes the cortical extent of functional networks.