Bromer C, Bartol TM, Bowden JB, Hubbard DD, Hanka DC, Gonzalez PV, Kuwajima M, Mendenhall JM, Parker PH, Abraham WC, Sejnowski TJ, Harris KM (2018) Long-term potentiation expands information content of hippocampal dentate gyrus synapses. PNAS. (PDF; Supplemental)
The brain has the capacity to store an immense amount of information at the synapses. But whether this capacity can be rapidly modified by experience is not known. Together with key collaborators Professor Terrence Sejnowski at The Salk Institute for Biological Studies in California and Professor Wickliffe Abraham at the University of Otago in Dunedin, New Zealand, the Harris Lab has created three-dimensional reconstructions of individual synapses and applied Information Theory to the resulting data. We have shown that information storage capacity is surprisingly variable across different brain regions. Importantly, we show that the capacity for information storage is not fixed but can be enhanced by learning-related neural activity. Thus, this new paper provides new insights into how new experiences can be stored in the brain while maintaining overall stability. Applying Information Theory to understand function from variation in synapse structure is the focus of a major NSF NeuroNex grant that was recently funded to Harris and Sejnowski together with Dr. James Carson at TACC at UT-Austin.
The gzipped tar file contains the output text files from Blender Reconstructions of EM Data and accompanying Python analysis scripts.
In this movie clip, a dendrite from the potentiated condition is rotated about its longitudinal axis as each component of the scene is added sequentially. The movie opens with the intermediate dendritic segment (solid yellow) with two of the spines that are later shown to be a same-dendrite same-axon (SDSA) pair colored blue. At 18 s, the rest of the reconstructed dendritic segment (translucent yellow), including the spines and synapses (red), is added. At 36 s, the axon (white) participating in the SDSA pair is added. At 55 s, the rest of the axons (green) that formed synapses with one spine head from the intermediate dendritic segment are added. (Scale cube: 1 µm3.) These three-dimensional reconstructions were all necessary components for determining the information content stored in the variation in the structure of synapses in the hippocampus.