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CBB talk series
The Cognitive Brown Bag (CBB) is a graduate student organized talk series, primarily attended by the faculty, graduate students, and staff from the cognitive labs at Dartmouth College. A list of past CBB talks can be found here.
Organizers: Benjamin Graul (Wager lab) , Zizhuang Miao (Wager lab), and Deepasri Prasad (Robertson lab).
Academic year 2025-2026
All talks will be held from 1:10-2:10 p.m., unless otherwise noted.
Spring term
| Date | Speaker | Title | Abstract |
| Tues, 4/21 | |||
| Deepasri Prasad (Dartmouth College, Robertson lab) | Re-examining sensory reinstatement during visual recall in category-selective visual cortex | Our classic understanding of visual recall proposes that the same category-selective visual areas activated during perception are similarly reactivated when recalling their preferred category. However, recent work has complicated this “sensory reinstatement” hypothesis, demonstrating variations like topographic shifts between encoding and recall in scenes (Steel et al., 2021) and intermixed neuronal subpopulations selective for encoding and recognition in faces (Quian Quiroga et al., 2023; Chen et al., 2024). Given this variety, are there common principles or characteristic differences across how category-selective areas implement sensory reinstatement? Here, we examine the activation patterns during perception and recall in a range of category-selective visual areas using fMRI. Participants (N=25) performed visual recall and perception tasks in the scanner. For recall, participants vividly recalled self-generated personally familiar faces, scenes, objects, and body parts. For perception, participants viewed dynamic videos from the same categories. Using face-, body-, and scene-selective functional areas defined from independent atlases, we identified category-specific regions of interest in both tasks. We see that all areas showed some degree of sensory reinstatement, with significant overall univariate activity for their preferred category in both perception and recall. However, how this sensory reinstatement is implemented differs depending on the area. For most areas, the most selective voxels for perception were similarly the most selective for recall. However, in scene-selective PPA and OPA, the top-most selective voxels differed between the tasks. This effect is driven by a significant anterior shift in recall versus perceptual activity (all p-values<0.001). Together, this indicates that no single implementation of sensory reinstatement is common across all visual categories; instead, the reinstatement method might reflect unique mnemonic demands of each visual category. | |
| Peter Angeli (Dartmouth College, Robertson lab) | A Voxel-Level Visuospatial Code Structures Hippocampal-Cortical Interactions to Support Memory Dynamics | Episodic memory is tied to specific sensory experiences, requiring close interplay between sensory and mnemonic systems. The hippocampus uniquely spans both systems, yet relatively little is known about how it efficiently integrates sensory and mnemonic information. Building from recent work showing that a bivalent (i.e. positive and negative) retinotopic code scaffolds interactions across higher-order perceptual and mnemonic regions in cortex, we asked whether a similar code structures intra-hippocampal activity, as well as hippocampal-cortical interactions. To explore this possibility, we leveraged densely sampled high-resolution 7T functional MRI from the Natural Scenes Dataset along with voxel-scale visual population receptive field (pRF) modeling and individualized resting state networks. We found a robust voxel-scale retinotopic code in the human hippocampus, comprised of an equal proportion of pRFs with positive and negative responses to visual stimulation. This bivalent code continued to shape spontaneous voxel-scale dynamics even during independent resting-state fixation, both within the hippocampus and between the hippocampus and cortex, particularly to mnemonic Default Network A. Finally, activity during a multi-session continuous memory task revealed preferential recruitment of cortical positive pRFs for encoding and negative pRFs for retrieval, suggesting a functional role for this bivalent retinotopic code in structuring visual memory dynamics. Together, these findings suggest that a bivalent retinotopic code organizes hippocampal sensory-mnemonic information processing. | |
| Tues, 4/28 | |||
| Eunhye Choe (Dartmouth College, Tse lab) | |||
| Atlas Shahamati (Dartmouth College, Soltani lab) | |||
| Tues, 5/12 | |||
| Zizhuang Miao (Dartmouth College, Wager lab) | |||
| Antônio Mello (Dartmouth College, Duchaine lab) | |||
| Tues, 5/26 | |||
| Aryan Yazdanpanah (Dartmouth College, Soltani lab) | |||
| Eun Tack Cho (Dartmouth College, Murray lab) |