Meeting Reports: Neuronal Ensembles 2024

On May 2, 2024, we hosted an international symposium on Neuronal Ensembles. The meeting took place online, with over 900 registrants from over the world. This was the third instance of a meeting focused on ensembles, again organized by Rafael Yuste from Columbia University, Rosa Cossart, from INMED, France, and Emre Yaksi, from the University of Trondheim Norway. This year’s edition focused on the comparison between human data and results from animal experiments. The meeting started with a welcome from the organizers, who defined ensembles as coactive groups of neurons that can happen in response to sensory stimulation or motor action, but also occur spontaneously. Thus, the focus phenomenology is on the existence of an endogenous circuit motif that can be engaged in different functional conditions.

The first speaker was Madeleine Lancaster from the Medical Research Council’s Laboratory of Molecular Biology in Cambridge, UK. Lancaster is the researcher that first pioneered human organoids and explained how they are layered, like the developing brain. She argued that what distinguishes human versus other primates is the fact that we have a protracted neurogenic period. But instead of 3D organoids, she presented her results from air-liquid interphase cultures, which have a denser neuropil without cell death, or holes which are the sign of damage. These neurons have dendritic spines, action, potentials, long-ranged connectivity, which can be functional, as demonstrated with microelectrode array recordings. Moreover, in mouse cocultures of spinal cord and muscle, spine cord activity can generate and mouse contractions. She addressed the differences between human and mouse cultures, arguing, that the later neurogenesis of humans leads to the slower maturation of the culture. She also spoke about cell replacement therapy for disease and the limitation of human organoids. She discussed briefly the work of the Pasca lab at Stanford that has maintained up to 270 days and observe a GABA switch which happens in human development. But she argued that interphase cultures a greater prospect since they can be cultured in the long term and show maturation of NMDA. All neuronal cell types were apparently generated in these cultures, with the exception of microglia.

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