Neuronal Ensembles: Emergent Units of Cortical Function?

Rafael Yuste, MD, PhD Neurotechnology Center, Dept., Biological Sciences, Columbia University The design of neural circuits, with large numbers of neurons interconnected in vast networks, strongly suggest that they are specifically build to generate emergent functional properties (1). To explore this hypothesis, we have developed two-photon holographic methods to selective image and manipulate the activity of neuronal populations in 3D in vivo (2). Using them we find that groups of synchronous neurons (neuronal ensembles) dominate the evoked and spontaneous activity of mouse primary visual cortex (3). Ensembles can be optogenetically imprinted for several days and some of their neurons trigger the entire ensemble (4). By activating these pattern completion cells in ensembles involved in visual discrimination paradigms, we can bi-directionally alter behavioral choices (5). Our results are consistent with the possibility that neuronal ensembles are functional building blocks of cortical circuits.