Segregation and integration between visuo-spatial attention and semantic memory across large-scale brain networks

Visuo-spatial attention and semantic memory are supported by distinct, largely competing brain networks, yet they are frequently engaged together in daily life. How these networks interact during combined tasks remains unexplored. We conducted a factorial fMRI experiment in which 25 participants performed a novel task requiring visuo-spatial attention, semantic judgment, or both. Covert shifts of attention towards cued lateral location activated bilateral parietal (PEF), frontal eye fields (FEF), and anterior insula. Categorizing a word as referring to a living or non-living entity activated a lateral parietal region (LaP) between the dorsal tip of the angular gyrus and the lateral bank of the intraparietal sulcus, along with the left inferior frontal gyrus (IFG), superior temporal sulcus, inferior temporal lobe and bilateral anterior insula. Notably, the anterior insula was active in both conditions. Dynamic causal modeling showed excitatory-inhibitory parieto-frontal loops driving attention (PEF→FEF) and semantic processing (LaP→IFG) separately, but in the combined condition frontal-to-parietal feedback became excitatory, reflecting stronger integration, with the anterior insula driving overall connectivity. These findings identify LaP as a novel region supporting semantic processing of linguistic stimuli, and highlight the anterior insula as a key hub integrating attentional and semantic networks under concurrent cognitive demands.