A group of neurones that act together in processing a certain task. One neuron can be part of several cell assemblies Donald O. Hebb (1949), in his book The organization of behavior: a neuropsychological theory, introduced the notion of cell assemblies into psychology. According to him, stimuli, objects, but also more abstract psychological entities (e.g., concepts, ideas, memory) are represented in the brain by simultaneous activation of groups of neurons he referred to as cell assemblies. At the root of a definition of a cell assembly is connectivity (i.e., cells forming an assembly are connected by relatively numerous and/or strong mutual excitatory synapses). Moreover, if a sufficient number of cells in an assembly are stimulated, all cells in it tend to become co-activated. In his theory of cell assemblies, Hebb postulated specifically that synapses are strengthened when both connected cells are activated simultaneously within a certain time window. This learning mechanism is now referred to as the `Hebbian learning rule’.
See Hebbian learning, Neuron, Synapse