This book is part memoir, part scientific treatise, and part metaphysical exploration. Koch is a professor of biology and engineering at Cal Tech, who is also well versed in philosophy of mind. He was a protege of Francis Crick, working together on issues of neurobiology and the nature of consciousness over the years. Koch’s ongoing goal is to find the explicit links from the objective world to the subjective one. He terms himself a romantic reductionist- a “reductionist because I seek quantitative explanations for consciousness in the ceaseless and ever-varied activity of billions of tiny nerve cells, each with their tens of thousands of synapses; romantic, because of my insistence that the universe has contrails of meaning that can be deciphered in the sky above us and deep within us. Meaning in the sweep of its cosmic evolution, not necessarily in the lives of the individual organisms within it.”
Koch seeks to find where exactly in the brain qualia resides. Philosophers of mind define qualia (plural of quale) as raw feelings, the elements that together make up any one conscious experience. A “condition necessary for any one specific conscious sensation is an active and functioning cortico-thalamic complex. This complex includes, first and foremost, the neocortex and the closely allied thalamus underneath it…. Bioelectrical activity in discrete regions of the cerebral cortex and its satellites is essential for the content of conscious experience…. Pyramidal neurons are the workhorses of the cerebral cortex. They account for about four of every five cortical neurons and are the only ones that convey information from one region to other sectors within or outside the cortex, such as the thalamus, the basal ganglia, or the spinal cord…. It is there, in the prefrontal cortex, and especially in its dorsolateral division, that the higher intellectual functions- problem solving, reasoning, and decision making- are located.”
One of Koch’s primary missions is to dig even deeper into neuroanatomy to minutely map out every single neuron and synaptic connection in the human brain. This is no small task. Koch stresses “the astounding heterogeneity of neurons. The approximately 100,000 neurons packed below each square millimeter of cortex…. are highly heterogenous. They can be distinguished based on their location, the shape and morphology of their dendrites, the architecture of their synapses, their genetic makeup, their electrophysiologic character, and the places to which they send their axions.” Therefore, the first step in this long process of discovery is mapping out the smaller and simpler mouse brain. (Work he is leading with the Allen Institute for Brain Science.) This is fruitful because “neither at the genomic nor at the synaptic, cellular, or connectional levels are there qualitative differences between mice, monkeys, and people.” Scientists usually work on mice and monkeys when human experiments would be too risky or cruel. But Koch has also worked on epileptic patients, who already required brain surgery, as well as many non-invasive studies on vegetative patients and normal human subjects. He most frequently uses an electroencephalograph (EEG) or an fMRI to monitor patients, both awake and in various stages of sleep while conducting his experiments. “It is the cortico-thalamic complex that provides the phenomenal content of dreams.” Most of Koch’s experiments work with vision, particularly when distracted, split, or masked. Even though your eyes are constantly moving rapidly, in what are known as saccades, “it is neurons in the higher reaches of the visual cortex that produce your perception that the world is stationary.”
Crick and Koch’s foremost supposition is that consciousness evolved as an adaptive success because it allowed for the ability for long range planning. Koch explicitly writes, “the function of consciousness is planning. Patients bereft of part or all of their prefrontal cortex have difficulty planning for the near or the distant future. We took this to imply that the neural correlates of consciousness must include neurons in the prefrontal cortex.” Crick and Koch also speculate that it is vast and varied communication back and forth between neurons in different parts of the brain, so-called neuron loops, which are essential to consciousness. “Clinicians recorded the EEG of two classes of severely brain-injured patients, those that remain unconscious and those that recover at least some measure of awareness. They found that the critical difference is the presence or absence of communication between prefrontal regions and temporal, sensory cortical regions in the back. If such feedback is present, consciousness is preserved.” Although the brain is somewhat pliable, its regions are often fairly specific. “Semir Zeki at University College London coined the term essential node for the portion of the brain that is responsible for a particular conscious attribute. One region of the visual cortex contains an essential node for the perception of color; several such regions are involved in face perception and in the sense of visual movement. Parts of the amygdala are essential to the experience of fear. Damage to any one node leads to loss of the associated perceptual attribute, although other conscious attributes remain.” In an experiment on patients already requiring brain surgery, scientists found “startling selectivity at the level of individual nerve cells…. One hippocampal neuron responded only to seven different photos of the movie star Jennifer Anniston but not to pictures of other blonde women or actresses. Another cell in the hippocampus fired only to the actress Halle Berry, including a cartoon of her and her name spelled out.” Somehow, the brain was recognizing the many different tokens within one singular type (Halle Berry) and grouping them all as alike. Another interesting experiment showed that attention and conscious thought do not occur in tandem. “Action can indeed be faster than thought, with the onset of corrective motor action preceding conscious perception by about a quarter of a second.”
Koch ends by going on to speculate about the grand nature of consciousness. “I believe that consciousness is a fundamental, an elementary, property of living matter. It can’t be derived from anything else; it is a simple substance.” Koch lends credence to Giulio Tononi’s functionalist idea of consciousness as integrated information. “Any conscious state is extraordinarily informative. In fact, it is so specific that you will never re-experience the exact same feeling- ever!…. Any conscious state is a monad, a unit- it cannot be subdivided into components that are experienced independently.” This duality of integration and differentiation are what create the conscious system. “The conscious sensation arises from integrated information; the causality flows from the underlying physics of the brain, but not in any easy-to-understand manner. That is because consciousness depends on the system being more than the sum of its parts.” This is all very speculative. Koch admits that it will require years of more research to come to any scientifically acceptable agreement on the true nature of consciousness, exactly where it resides, and exactly how it actually works. That discovery process is what he has made his life’s quest.
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