“The Cell Assembly: Mark II”, Paul M. Milner1957 (neuroscience)⁠:

This deals with a neural model, similar to Hebb’s, that is based on “association-of-ideas.” “Thus, one principle of learning—the binding of cells into a group by repeated simultaneous firing—fulfills a double role; when the newly added cells are predominantly primed by sensory input perceptual learning results; and when the new cells are primed by the firing of another cell assembly, associative learning results.”

…A neural model has been presented, based on an “association-of-ideas” paradigm of learning, similar to that used by Hebb. In it groups of neurons (cell assemblies) become representations of stimuli, and can then be linked together by being fired contiguously. The model differs from Hebb’s in that an inhibitory regulatory system is postulated which limits (to a minute fraction of the total) the number of cortical neurons that can fire simultaneously, and insures that those firing are dispersed as widely as possible. A further change is introduced to meet the paradox that cell assemblies can be associated with one another without losing their individuality and being submerged in a composite new cell assembly. In association, it is not the cells of one assembly that acquire connections with the cells of another; instead, cells primed, or sensitized, by the first assembly become incorporated into the second. Thus, one principle of learning—the binding of cells into a group by repeated simultaneous firing—fulfills a double role; when the newly added cells are predominantly primed by sensory input perceptual learning results ; and when the new cells are primed by the firing of another cell assembly, associative learning results.

Because the effect of priming lasts for many seconds, it is possible for a cell assembly to accumulate the sensitizations induced by the activities of a number of associated assemblies, and so increase the probability that it will itself fire.

The dual role of motivation—the facilitation of learning and the elicitation of responses—has been discussed in terms of the arousal effects of the nonspecific projection system on the postulated cortical network.