Neural Correlates of Object-Based Attention in Retinotopic Visual Cortex in a 100% Valid Cueing Task
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Authors
Lytchenko, Taissa K.
Issue Date
2024
Type
Thesis
Language
Keywords
Cue , Early Visual Cortex , FMRI , Neural Correlates , Object-based Attention , Visual Attention
Alternative Title
Abstract
A central debated question in the study of Object-Based Attention (OBA) is whether attention spreads automatically to the entire object (Chen & Cave, 2006) or whether the pattern of results is driven by other non-obligatory factors, such as prioritization of target locations (Shomstein & Yantis, 2002). However, virtually all behavioral measures attributed to OBA are based on examining performance on invalid-cue trials, the inclusion of which confounds the assessment of the automaticity hypothesis. A critical test of the hypothesis attention spreads over objects that lacks this confound would be to determine whether or not effects of OBA can be observed in a 100% valid cueing paradigm. In this paper we investigate the obligatory nature of OBA by leveraging the spatial specificity of functional magnetic resonance imaging (fMRI) and the retinotopic organization of the early visual cortex. We aimed to identify potential neural correlates of OBA in the complete absence of invalid trials. Participants perform a version of the classic two-rectangle OBA paradigm while simultaneously measuring changes in BOLD signals arising from retinotopically organized cortical areas V1, V2 and V3. In the first half of the experiment, we used the classic two-rectangle OBA paradigm except that the cue was 100% valid. In the second half, we reduced cue validity to more closely match standard OBA paradigms (runs containing invalid trials). We analyzed BOLD signals arising from our regions of interest in V1, V2, and V3 according to their topographic correspondences with the ends of the rectangles in the visual field and compared these. We then compared responses in each ROI according to where the cue had occurred (Cued, Uncued-Same-Object, Uncued-Other-Object location). We replicated this procedure in Experiment 2, but changed the layout of the two rectangles from a vertical to a horizontal configuration. Critical result: we observed statistically significant effects of OBA in V3 (Experiment 1) and V1-2 (Experiment 2) in both the 100% valid runs and in runs containing invalid trials. Moreover, the effects of OBA were no smaller in the 100% runs compared to runs containing invalid trials. Conclusion: we see BOLD modulation at the uncued locations consistent with neural correlates of OBA.