Attention functions as a filter mechanism that addresses the limitations of sensory processing by selecting the most behaviorally relevant inputs. Recent studies indicate that attention can select information based on the sensory modality of presentation, but it remains unclear if this intermodal selection utilizes shared attentional resources or independent pools for each modality. This research explores the neural mechanisms of sustained intermodal attention, examining the debate between common versus modality-specific attentional resources. Using frequency-tagged auditory and visual stimuli, the study recorded continuous electrophysiological brain responses in early sensory cortices through three experiments. These investigations aimed to determine if attention to a specific modality leads to modality-specific processing modulation, whether this modulation involves facilitation of attended stimuli, inhibition of unattended ones, or both, and if stimuli from different modalities compete for processing, suggesting a reliance on common resources. Results indicated that attentional modulation is modality-specific, involving facilitation of attended stimuli and inhibition of unattended ones. Additionally, competition for processing occurred within modalities but not across them. Overall, the findings support the idea that early sensory processing depends on modality-specific rather than common attentional resources.
