Summary

This chapter summarizes the key points of the preceding chapters and embarks on a number of speculations. It shows that the strength of the evidence for each of the preceding statements varies. On one hand, some propositions are based merely on the supposition that it would make sense if an anatomical or physiological feature functioned in a certain way (such as sensory processing by back-projections). On the other hand, the proposition for “time-chunking” seems irrefutable in view of the abundant evidence from masking experiments. Further, given the existence of time-chunking, then not only is the case for binding of sensory features by common rhythmical activity untenable, but one can also then look for neurophysiological activity that would fit in with time-chunking. Ultimately, this chapter presents both of these key speculations and the evidence for them and leaves the reader to decide for themselves.

Looking to the Future

This chapter considers the question of whether or not nonliving systems can acquire consciousness. It explores contemporary advances in technology, particularly in the field of artificial intelligence. The chapter also considers whether or not consciousness can be performed if inorganic matter replaced the components with which organisms experience consciousness. These and similar questions on nonhuman intelligence and consciousness are fleshed out with scenarios and thought experiments proposed throughout the 20th century, such as John Searle’s Chinese room argument and the archangel paradigm proposed by C. D. Broad. The chapter concludes with reflections on the human being’s inability to truly experience consciousness in the same way as nonhumans.

Concepts, Conferences, and Controversies

This chapter outlines the history of research meetings dealing with consciousness, beginning with that hosted by Herbert Jasper in the Laurentian mountains of Quebec in 1953. It starts, however, with a brief discussion on ancient scientific approaches to medicine, which was jump-started by the Greek physician, Hippocrates. Afterward, the chapter skips forward two millennia to major figures who made breakthroughs in the field of brain science. It also touches on a central debate that reached its climax a little later, as to which part of the brain was responsible for consciousness. The chapter considers whether it was the cerebral cortex, as had been the prevailing assumption, or if it was the brain stem.

More on Gnostic Units and Cortical Columns

This chapter returns to the subject of gnostic units discussed in Chapter 9, as well cortical columns, both of which form the building blocks of cortical function. Gnostic units are used to describe a neural assembly having knowledge (information). The chapter first expounds on gnostic units and how they relate to the concept/grandmother cells already discussed previously. It then goes on to consider the type of neural structure, which might correspond to a gnostic unit. At the simplest level, electrophysiological recordings have shown that a single neuron could be regarded as a gnostic unit. From here, the chapter conceives of a hierarchy of analyzers in the form of cortical columns. At the highest level will be the column(s) specific for a particular face or object—these cells will fire, and the face or object will be recognized by the conscious brain.

Who Else Is Conscious?

This chapter studies the behaviors of various animal species, as well as animal consciousness. It argues for the significance of such studies, for these indicate that they, the animals, share the property of consciousness with human beings. The chapter contends that animals are perfectly capable of language (and thus of thought), both vocal and signed. It is up to the humans then to undertake the challenge of deciphering these. To illustrate these points, the chapter looks at research done on various species of animals, from cats and dogs to dolphins and even insects. In so doing, this chapter it draws awareness to the fact that brains do not have to be built like that of humans to possess consciousness.

Making Sense of the Senses

This chapter describes the novel findings of David Hubel and Torsten Wiesel when recording from single cells in the primary visual cortex and how these findings supported the concept that the various features of the observed image underwent independent processing in parallel. Of the various sensory systems, the one about which most is known is the visual one. Vision is also the most complex sensory system, which is reflected in its large cortical territory. The chapter thus focuses on the sense of sight in particular as it explores the findings of Hubel and Wiesel. However, the chapter also presents an alternative to the now-classic Hubel–Wiesel scheme, one that, despite its fundamental differences, seems equally plausible.

Single Units and Grandmother Cells

This chapter turns to a more recent discovery in the human hippocampus, that of “concept” (or “grandmother”) cells. These grandmother cells are neurons that code for multiple aspects of the same person or object. The prediction that specific recognition cells were present in the brain had been made many years previously by vision scientists in Cambridge University and the Massachusetts Institute of Technology. Especially relevant for an understanding of conscious mechanisms was the observation that merely thinking about a person or image could increase the impulse firing rate of the corresponding concept cell, even when the person or image was no longer being seen. At about the same time Jerzy Konorski, in Warsaw, had argued for the existence of similar neurons (“gnostic units”) serving a number of functions.

Electricity Works

This chapter focuses on the electrical activity of the brain. It first highlights Richard Caton’s demonstration of slow waves in the rabbit brain before an audience of physicians in Edinburgh in 1875. Then the chapter turns to the impact of Hans Berger’s discovery of similar slow waves in the human brain and of the advent of electroencephalography. The chapter finishes with the remarkable technical accomplishment of Mircea Steriade in being able to record from the same single neuron during periods of sleep and wakefulness, thereby showing the enormous range of impulse firing frequencies possible. From here, the chapter considers if it is possible that it is simply the intensity of the cortical discharge, with its thalamic underpinning, that determines whether or not impulse activity enters into consciousness.

Awaking the Cortex

This chapter tells the story of the discovery of the reticular activating system. At the same time, the chapter traces various attempts to address the larger question of “waking” the cortex and bringing it to a state of consciousness. It turns to two scientists, Horace Magoun and Giuseppe Moruzzi, both of whom conducted experiments to explore the possible effects on the cerebral cortex of stimulating the brain stem. Since the brain’s reticular formation ended just below the thalamus on either side, it was logical to see if it might alter cortical excitability. The chapter shows how Magoun and Moruzzi came to the conclusion that, through its action on the excitability of the cortex, the reticular formation could control the wakefulness of the brain.

Mapping the Brain

This chapter turns to the next period in the history of brain studies. It follows up on the previous chapter’s discussion by pinpointing where exactly in the nervous system that consciousness takes place. This chapter thus takes the reader through the findings of the late 19th century that attempted to understand the inner workings of the cerebral cortex, particularly in three key areas: the motor, the visual, and the somatosensory. In doing so, the chapter shows that the identification of the motor and sensory areas accounted for rather more than half of the cortex. It briefly touches upon the questions raised by this topic—in particular the contribution to consciousness—before discussing other aspects of brain maps, including memory and plasticity.