Jieun Park¹ (), Soojin Park¹; ¹Department of Psychology, Yonsei University, Seoul, Korea

What are the systematic cues or transitions in the world that allow us to break down the seemingly unbroken flow of navigation into discrete locations, spaces, and key turning points? Past studies have shown that structural boundaries such as a wall or a doorway help chunk the memory of the events. Here, we asked how the structural boundary prominence and type are represented in the brain. Boundary prominence was determined by the prominence of a perceptual boundary: Hard Boundary (HB) showing a large boundary transition within scenes such as a clear walk-out from an indoor space to an outdoor space; Soft Boundary (SB) showing a subtle transition such as an outdoor patio to an outdoor space; and No Boundary (NB) with an absence of any perceptible boundary or transition. For each boundary prominence condition, four boundary types (Indoor-Outdoor, Doorway, Landmark, Turn) were presented in six second movie clips depicting a boundary transition episode. During scanning, participants (N=10) performed a color-dot judgment task to compare whether the color of the two dots presented sequentially on top of the video stimuli were the same or different. In half of the trials, the two dots were presented within the same boundary, in other half, they were presented across the boundary. The average inter-stimulus interval between the two dots were matched. Results show that the PPA demonstrated a stair-cased activity pattern, with the highest activity for the hard boundary, followed by soft and no boundary. Both the RSC and OPA showed a main effect of boundary prominence, driven primarily by differences between hard and no boundaries. Boundary prominence interacted with type in the PPA and RSC, but not in the OPA. Preliminary behavioral analysis suggests hard boundaries may enhance dot color comparison accuracy across boundaries when dots are presented in segregation across the boundary.

Acknowledgements: This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIP)(NRF-2023R1A2C1006673)