Second, what we imagine and recall involves resonances between neural layers, stimulating activity that originated during perception. So imagination 'feels' like a recall of perception even if the exact perception had never taken place. What makes consciousness so puzzling is that the neural activity responsible for both perception and imagination provides a sensation of being an observer (the self) in an 'out-there' world. This sensation depends not only on sensory neural activity but also on virtually unconscious exploratory motor neural activity due to conscious curiosity or to unconscious habit, instinct or reflex.
Take the oculomotor system, for example, which has evolved to allow the eyes to move rapidly towards tiny changes in the field of view, to follow moving objects, to converge if something comes nearer, and even to move rapidly towards a perceived sound. It also interacts with memory to check hypotheses about partially seen objects and to predict their unseen parts. So the neural activity that supports conscious sensation not only involves sensory signals such as those generated by incident light on the retina or vibratory stimulation of the cochlea, but is clearly dependent on signals from the parts of the body that move the eyes and the head, and signals from touch. There is much evidence in neurology (for example in the work of Carlo Galletti, which began in 1989) that cells in various cortical areas only process sensory information as indexed by muscular action, creating inner representations of events that take place 'out there'. Some of this supporting unconscious neural activity is what Christof Koch and Francis Crick call “the zombie within”.
