The brain basis of a "consciousness monitor": scientific and medical significance.

Surgical patients under anesthesia can wake up unpredictably and be exposed to intense, traumatic pain. Current medical techniques cannot maintain depth of anesthesia at a perfectly stable and safe level; the depth of unconsciousness may change from moment to moment. Without an effective consciousness monitor anesthesiologists may not be able to adjust dosages in time to protect patients from pain. An estimated 40,000 to 200,000 midoperative awakenings may occur in the United States annually. E. R. John and coauthors present the scientific basis of a practical "consciousness monitor" in two articles. One article is empirical and shows widespread and consistent electrical field changes across subjects and anesthetic agents as soon as consciousness is lost; these changes reverse when consciousness is regained afterward. These findings form the basis of a surgical consciousness monitor that recently received approval from the U.S. Food and Drug Administration. This may be the first practical application of research on the brain basis of consciousness. The other John article suggests theoretical explanations at three levels, a neurophysiological account of anesthesia, a neural dynamic account of conscious and unconscious states, and an integrative field theory. Of these, the neurophysiology is the best understood. Neural dynamics is evolving rapidly, with several alternative points of view. The field theory sketched here is the most novel and controversial.

Attention versus consciousness in the visual brain: differences in conception, phenomenology, behavior, neuroanatomy, and physiology.

A common confound between consciousness and attention makes it difficult to think clearly about recent advances in the understanding of the visual brain. Visual consciousness involves phenomenal experience of the visual world, but visual attention is more plausibly treated as a function that selects and maintains the selection of potential conscious contents, often unconsciously. In the same sense, eye movements select conscious visual events, which are not the same as conscious visual experience. According to common sense, visual experience is consciousness, and selective processes are labeled as attention. The distinction is reflected in very different behavioral measures and in very different brain anatomy and physiology. Visual consciousness tends to be associated with the "what" stream of visual feature neurons in the ventral temporal lobe. In contrast, attentional selection and maintenance are mediated by other brain regions, ranging from superior colliculi to thalamus, prefrontal cortex, and anterior cingulate. The author applied the common-sense distinction between attention and consciousness to the theoretical positions of M. I. Posner (1992, 1994) and D. LaBerge (1997, 1998) to show how it helps to clarify the evidence. He concluded that clarity of thought is served by calling a thing by its proper name.

Metaphors of consciousness and attention in the brain.

Scientific metaphors have long provided heuristic tools for approaching novel problems.Today, the neurobiology of consciousness and attention is a central concern, presenting formidable conceptual and empirical challenges. Many current ideas fit the broad theme of a theater metaphor; this idea can be worked out in detail, resulting in relevant, testable hypotheses.

Some essential differences between consciousness and attention, perception, and working memory.

When "divided attention" methods were discovered in the 1950s their implications for conscious experience were not widely appreciated. Yet when people process competing streams of sensory input they show both selective processes and clear contrasts between conscious and unconscious events. This paper suggests that the term "attention" may be best applied to the selection and maintenance of conscious contents and distinguished from consciousness itself. This is consistent with common usage. The operational criteria for selective attention, defined in this way, are entirely different from those used to assess consciousness. To illustrate the scientific usefulness of the distinction it is applied to Posner's (1994) brain model of visual attention. It seems that features that are often attributed to attention-like limited capacity-may more accurately be viewed as properties of consciousness.

Tutorial commentary: surprisingly small subcortical structures are needed for the state of waking consciousness, while cortical projection areas seem to provide perceptual contents of consciousness.

The evidence can therefore be summarized as follows: (1) RF, nRt, and ILN activity seem to be necessary but not sufficient for conscious experience. (2) Stimulus representation in primary sensory projection areas also seems to be necessary but not sufficient for conscious perceptual experience (Weiskrantz, 1980). The simplest hypothesis is that both components are necessary and sufficient to support conscious perceptual experience.

Steps toward healing: false memories and traumagenic amnesia may coexist in vulnerable populations.

Child abuse is surely the most agonizing psychological issue of our time. We decry the tendency to polarize around the either-or dichotomy of "recovered versus false memories," when both are likely to occur. Memory researchers seem to generalize from the mild, one-shot stressors of the laboratory to the severe repeated traumas reported by abused populations, an inferential leap that is scientifically dubious. Naturalistic studies show (a) some post-traumatic memory impairment (not just forgetting, but difficulty remembering in spite of repeated efforts); (b) dissociativity, such as emotional numbing, detachment, and the like; but also (c) increased suggestibility (Spiegel & Cardena, 1991). About 20% of the normal population is highly suggestible, and in these individuals it is trivially easy to show suggested amnesia, detachment, perceptual blocking, etc., as well as to suggest dramatically false memories. It is therefore vital to assess suggestibility and dissociativity in traumatized populations. Adult survivors of abuse may show both more false "memories" and more "false forgetting" than the normal population.

How does a serial, integrated and very limited stream of consciousness emerge from a nervous system that is mostly unconscious, distributed, parallel and of enormous capacity?

Much of the nervous system can be viewed as a massively parallel, distributed system of highly specialized but unconscious processors. Conscious experience on the other hand is traditionally viewed as a serial stream that integrates different sources of information but is limited to only one internally consistent content at any given moment. Global Workspace theory suggests that conscious experience emerges from a nervous system in which multiple input processors compete for access to a broadcasting capability; the winning processor can disseminate its information globally throughout the brain. Global workspace architectures have been widely employed in computer systems to integrate separate modules when they must work together to solve a novel problem or to control a coherent new response. The theory articulates a series of increasingly complex models, able to account for more and more evidence about conscious functioning, from perceptual consciousness to conscious problem-solving, voluntary control of action, and directed attention. Global Workspace theory is consistent with, but not reducible to, other theories of limited-capacity mechanisms. Global workspace architectures must show competition for input to a neural global workspace and global distribution of its output. Brain structures that are demonstrably required for normal conscious experience can carry out these two functions. The theory makes testable predictions, especially for newly emerging, high-speed brain imaging technology.

Effects of cognitive set upon laboratory induced verbal (Freudian) slips.

Subjects participated in either of three treatments of a task which elicits verbal slips. With equal chance probabilities of eliciting verbal slips related either to electricity or to sex, subjects receiving a situational cognitive set toward electric shocks made more electricity-type verbal slips than sex-type errors, while the opposite was true for a situational cognitive set toward sex, and no difference occurred for a neutral cognitive set. Results provide insight into psycholinguistic processing of both naturally occurring verbal slips and normal error-free speech.