Tyler Bonnen, Ph.D. Student and Dawn Finzi, Graduate Student in the Department of Psychology, Stanford University
Title: On structure and function: White matter connections from early visual cortex scaffold the representation of visual space in face-selective regions
Abstract: The human face-processing network can be divided along two distinct streams: ventral occipito-temporal cortex containing IOG-faces, pFus-faces, and mFus-faces, and lateral occipito-temporal cortex containing pSTS-faces and mSTS-faces. Ventral regions are thought to be involved in processing face identity, while lateral regions are involved in processing dynamic aspects of faces. Despite these differences in function within an already highly specialized network, the anatomical or computational origins driving these differences remain unknown. Using a novel mapping stimulus (toonotopy) and population receptive field modeling in 21 participants, we find that ventral and lateral face-selective regions differentially code visual space. Ventral face-selective regions show a dense coverage of the center of the visual field (foveal bias), whereas lateral face-selective regions show a uniform coverage of the contralateral visual field extending to the periphery. To understand in what way white matter connections constrain the differential visual field coverage across face-selective regions, subjects participated in a second diffusion MRI experiment and anatomically constrained tractography. Examination of the distribution of white-matter connections from early visual cortex (EVC) to face-selective regions reveals that white matter tracts to ventral face-selective regions originate more foveally in EVC than those projecting to lateral face-selective regions. Together, these findings demonstrate that the anatomical and functional segregation of face-selective regions into two streams has a structural foundation that aligns with a differential processing of visual space across the two streams.
Title: Formalizing involvement of the Medial-Temporal Lobe in perceptual tasks: A meta-analytic, computational, and behavioral approach
Abstract: Animals rapidly transform sensory experience into memory. In the mammalian brain, perirhinal cortex (PRC) often plays a critical role in this process; As a Medial Temporal Lobe (MTL) structure implicated in memory-related behaviors, PRC receives direct inputs from numerous high-level sensory regions. Yet there has been an enduring debate in the memory literature over whether PRC is also necessary for certain perceptual processes. In this talk I'll sketch out an approach we've developed to formalize the perceptual demands in tasks considered to be diagnostic of PRC involvement in perception. This computational, meta-analytic, and behavioral approach is our first step towards formalizing how perceptual information is transformed in the service of memory-related behaviors.