Preface : consciousness redux -- What is consciousness? -- Who is conscious? -- Animal consciousness -- Consciousness and the rest -- Consciousness and the brain -- Tracking the footprints of consciousness -- Why we need a theory of consciousness -- Of wholes -- Tools to measure consciousness -- The uber-mind and pure consciousness -- Does consciousness have a function? -- Computationalism and experience -- Computers can't simulate experience -- Consciousness : here, there but not everywhere -- Coda : why this (...) matters -- References -- Notes. (shrink)

In "The Quest for Consciousness," Caltech neuroscientist Christof Koch explores the biological basis of consciousness.

Illusions that produce perceptual suppression despite constant retinal input are used to manipulate visual consciousness. Here we report on a powerful variant of existing techniques, Continuous Flash Suppression. Distinct images flashed successively around 10 Hz into one eye reliably suppress an image presented to the other eye. Compared to binocular rivalry, the duration of perceptual suppression increased more than 10-fold. Using this tool we show that the strength of the negative afterimage of an adaptor was reduced by half when it (...) was perceptually suppressed by input from the other eye. The more likely the adaptor was completely suppressed, the larger the reduction of the afterimage intensity. Paradoxically, trial-to-trial visibility of the adaptor did not correlate with the degree of suppression. Our results imply that formation of afterimages involves neuronal structures that access input from both eyes, but that do not correspond directly to the neuronal correlates of perceptual awareness. (shrink)

This book originated at a small and informal workshop held in December of 1992 in Idyllwild, a relatively secluded resort village situated amid forests in the ...

Aftereffects induced by invisible stimuli constitute a powerful tool to investigate what type of neural information processing can occur in the absence of visual awareness. This approach has been successfully used to demonstrate that awareness of oriented gratings or translating stimuli is not necessary to obtain a robust orientation-specific or motion-specific aftereffect. We exploit motion-induced blindness to investigate the related question of the influence of visual awareness on the formation of negative afterimages. Our results show that MIB does not affect (...) the persistence and intensity of afterimages. Thus, there is no significant contribution to the formation of afterimages beyond the sites mediating MIB. (shrink)

We agree with Block's basic hypothesis postulating the existence of phenomenal consciousness without cognitive access. We explain such states in terms of consciousness without top-down, endogenous attention and speculate that their correlates may be a coalition of neurons that are consigned to the back of cortex, without access to working memory and planning in frontal cortex.

We argue that the current known anatomy of connections between the intralaminar nuclei of the thalmus and visual cortical areas makes it unlikely that neuronal activity in the ILN mediates visual awareness.

What is the relationship between a visual percept and the underlying neuronal activity in parts of the brain? This manifesto reviews the theoretical framework of Crick and Kochfor answering these questions based on the neuroanatomy and physiology of mammalian cortex and associated subcortical structures. This evidence suggests that primates are not directly aware of neural activity in primary visual cortex, although they may be aware of such activity in extrastriate cortical areas. Psychophysical evidence in humans supporting this hypothesis is discussed.

The target article misrepresents the foundations of integrated information theory and ignores many essential publications. It, thus, falls to this lead commentary to outline the axioms and postulates of IIT and correct major misconceptions. The commentary also explains why IIT starts from phenomenology and why it predicts that only select physical substrates can support consciousness. Finally, it highlights that IIT's account of experience – a cause–effect structure quantified by integrated information – has nothing to do with “information transfer.”.

In which a scientist searches for an empirical explanation for phenomenal experience, spurred by his instinctual belief that life is meaningful. What links conscious experience of pain, joy, color, and smell to bioelectrical activity in the brain? How can anything physical give rise to nonphysical, subjective, conscious states? Christof Koch has devoted much of his career to bridging the seemingly unbridgeable gap between the physics of the brain and phenomenal experience. This engaging book--part scientific overview, part memoir, part (...) futurist speculation--describes Koch's search for an empirical explanation for consciousness. Koch recounts not only the birth of the modern science of consciousness but also the subterranean motivation for his quest--his instinctual belief that life is meaningful. Koch describes his own groundbreaking work with Francis Crick in the 1990s and 2000s and the gradual emergence of consciousness as a legitimate topic for scientific investigation. Present at this paradigm shift were Koch and a handful of colleagues, including Ned Block, David Chalmers, Stanislas Dehaene, Giulio Tononi, Wolf Singer, and others. Aiding and abetting it were new techniques to listen in on the activity of individual nerve cells, clinical studies, and brain-imaging technologies that allowed safe and noninvasive study of the human brain in action. Koch gives us stories from the front lines of modern research into the neurobiology of consciousness as well as his own reflections on a variety of topics, including the distinction between attention and awareness, the unconscious, how neurons respond to Homer Simpson, the physics and biology of free will, dogs, Der Ring des Nibelungen, sentient machines, the loss of his belief in a personal God, and sadness. All of them are signposts in the pursuit of his life's work--to uncover the roots of consciousness. (shrink)

The following interview explores neuroscientist Christof Koch's participation in the adversarial collaboration, testing the integrated information theory (IIT) of consciousness against the global neuronal workspace theory (GNW). The interview offers a current update on the adversarial project and then pivots to Koch's responses to three standing critiques of IIT, which include the inexactness of IIT's measures of the neural correlates of consciousness, the charge that IIT implies an unwieldy panpsychism, and the claim that IIT conflates its measures (...) with consciousness. (shrink)

In the long history of the exploration of consciousness from the earliest days of antiquity, the mysterious occurrence of consciousness has been attributed to the existence of hearts, brains, certa...

A philosopher argues that state-sponsored cyberattacks against central military or civilian targets are always acts of war. What is this philosopher doing? According to conceptual analysts, the philosopher is making a claim about our concept of war. According to philosophical realists, the philosopher is making a claim about war per se. In a quickly developing literature, a third option is being explored: the philosopher is engineering the concept of war. On this view, the philosopher is making a proposal about which (...) concept we should have – even if it deviates from the extant concept, and even if it does not capture ‘what war really is’. The activity or method of proposing such revisionary definitions, as well as the metaphilosophical reflection on it, has become known as conceptual engineering. (shrink)