Homare Yamahachi

Licenciado, University of Buenos Aires
Circuit Dynamics of Adult Visual Cortex
presented by Charles D. Gilbert

Homare (Matias) Yamahachi did his undergraduate degree in biology at the faculty of natural sciences, University of Buenos Aires, Argentina. His work involves making a window on the living brain to look for changes in brain circuitry that are associated with sensory experience and learning. His studies combined fluorescent labeling of neurons and their connections by gene transfer with viral vectors. This technique was combined with high-resolution two-photon imaging, which allowed him to image individual synapses, all in the intact, living brain. While the study of cortical circuitry had previously been done with postmortem anatomical tools, these tools did not allow one to see the circuit dynamics. Using high-resolution in vivo imaging, Matias, along with his collaborators, found that the circuits of the visual cortex are highly dynamic, turning over synapses at a rate of seven percent per week. And these changes occurred in the adult brain. Extending these studies to a model where he altered sensory experience, he found even more dramatic changes in cortical circuits, with very rapid alterations in circuitry involving an exuberant effluorescence of new connections paralleled by a pruning of old connections. These results led to a new view of brain circuitry. While the old view held that the connections in the brain are fixed after a critical period early in postnatal life, these results point to an ongoing process of sculpting cortical circuits, with new connections being formed and old connections being eliminated.

Matias’s interests lie at the interface of technology and biology, and going forward he would like to continue engineering new experimental approaches, while applying them to important biological problems.