On some occasions, a particular stimulus will evoke the firing of one of the neurons. The neuron that is activated will be activated whenever the subject sees the same object, but not other objects.
[In an experiment] carried out by a group of scientists at UCLA and reported in 2009 in the journal Science… the cell fired virtually identically during the perceptual and imaginative aspect of the experiment — remarkable evidence that identical cell assemblies/mental models are activated during sensory perception and imaginative recall. Supporting evidence comes from functional imaging studies where it is found that the brain areas activated during visual perception of an object largely overlap the brain areas activated when subjects are asked to imagine the appearance of the same object.
John Kubie (BrainFacts.org) | Perception and Imagination: A neuroscientist’s perspective