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Contributed Talk Session: Wednesday, August 5, 2:00 – 3:00 pm, Skirball Theater
Poster A in Poster Session A: Tuesday, August 4, 9:30 – 11:15 am, Kimmel Center, Shorin & Rosenthal Rooms

Recycling and Co-option Are Dissociable Mechanisms of Cortical Reorganization

Lauren S Aulet¹; ¹University of Massachusetts at Amherst

Presenter: Lauren S Aulet

When children learn to read, a region of ventral temporal cortex becomes selective for written words, yet this territory evolved long before writing existed. The dominant account of this phenomenon, cortical recycling, proposes that literacy reshapes prior visual representations to serve reading. However, recent work reveals conflicting evidence about which representations are recycled and whether modification is even necessary. We propose that these findings reflect two dissociable mechanisms that have been conflated under a single label. We trained ResNeXt-50 deep neural networks on infant egocentric video (SAYCam) using DINO self-supervised learning and then fine-tuned them on letter classification, tracking channel-level category selectivity. Limb-selective channels show high enrichment among newly letter-selective channels and high feature transformation: they are recycled. Face-selective channels show equally high enrichment but minimal feature transformation: they are co-opted, with a new downstream readout exploiting their existing features. Both mechanisms operate simultaneously on different neural populations during the same learning event, with the determining factor being whether a channel's existing features are already informative for the new task. We propose recycling and co-option as a more precise vocabulary for understanding how the brain repurposes existing circuits for culturally novel skills.

Topic Area: Computational Models of Vision & Visual Cortex