Roger Penrose's effort is an extension and elaboration of his earlier book, The Emperor's New Mind . The six laminae of the cerebral cortex with the apical dendrites of pyramidal cells of laminae II, III and IV, which bunch and end in tufts. From How the Self Controls the Brain . Eccles views the mind as being outside of the physical universe, but interactive with it. This view, called interactionist dualism, hails back at least as far as Descartes, and it was also the view of Sir Charles Sherrington, Eccles's mentor.
Dualism places a detailed understanding of mind and consciousness beyond the reach of science.
Eccles claims to have identified the physical site and physical mechanism whereby the nonphysical mind influences the brain. Eccles hypothesizes that it is the synaptic input to pyramidal neurons in the cortex that can be influenced by the mind. Mental intentions are hypothesized to increase the probability of synaptic-vesicle exocytosis. The Eccles model actually requires that the probability of exocytosis be influenced by physical adjustments no greater than the quivering of a single hydrogen atom. It is doubtful that the trigger mechanism for exocytosis requires so little in the way of physical movement, but there is an even greater difficulty with this model.