P242 Cytoelectric coupling: How electric fields tune Hebb’s cell assemblies
Dimitris A. Pinotsis1,2, Earl K. Miller2
1Department of Psychology, City St George's —University of London, London EC1V 0HB, United Kingdom
2 The Picower Institute for Learning & Memory and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
*Email: pinotsis@mit.edu
Introduction
Hebb introduced cell assemblies in his seminal work about 70 years ago. Today, cell assemblies are thought to describe groups of neurons coactivated when a certain memory, thought or percept is stored or processed. Here, we consider electric fields generated by cell assemblies.
Methods
We analyzed local field potentials (LFPs) recorded during a working memory task. These were obtained using high resolution, multi-electrode arrays and allow one to capture details of neural activity at the microscopic level. During the task, the animals, were shown a dot in one of six positions on the edge of a screen that would then go blank. After the delay period, the animals saccaded to the position they just saw marked. Using deep neural networks and biophysical modeling, we obtained the latent space associated with each memory. This allowed us to reconstruct the effective connectivity between different neuronal populations within the patch. Using a dipole model from electromagnetism, we predicted the electric field.
Results
We consider electric fields generated by cell assemblies. We show that they are more stable and reliable than neural activity. Fields appear to contain more information and to vary less across trials where the same memory was maintained. We here suggest that stability underlying memory maintenance is achieved at the level of the electric field. This is ‘above’ the brain, but still ‘of’ the brain. The field could direct the activity of participating neurons.
Discussion
Our analyses suggest that electric fields generated by neurons are causal down to the level of the cytoskeleton. Ephaptic coupling organizes neural activity, forming neural ensembles and low dimensional representations at the macroscale level. We suggest that this can go all the way down to the molecular level to stabilize and tune the cytoskeleton for efficient information processing. We call this the Cytoelectric Coupling hypothesis.
Acknowledgements
This work is supported by UKRI (ES/T01279X/1), Office of Naval Research (N00014-22-1-2453), The JPB Foundation, and The Picower Institute for Learning and Memory.
References
Pinotsis, D. A., & Miller, E. K. (2022). Beyond dimension reduction: Stable electric fields emerge from and allow representational drift. NeuroImage, 253, 119058.
Pinotsis, D. A., & Miller, E. K. (2023). In vivo ephaptic coupling allows memory network formation. Cerebral Cortex, 33(17), 9877-9895.
Pinotsis, D. A., Fridman, G., & Miller, E. K. (2023). Cytoelectric coupling: Electric fields sculpt neural activity and “tune” the brain’s infrastructure. Progress in Neurobiology, 226, 102465.
