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<jats:p>People often think of intelligence as quickness of thought or propensity for flashes of insight. But a variety of evidence suggests that such indicators of intelligence as language comprehension and problem-solving ability may instead depend on the ability to juggle lots of possibilities in the mind—that is, on working memory.</jats:p>

<jats:p>Ten years ago, any neurophysiologist who claimed to be looking for the neural basis of consciousness would have had a tough time being taken seriously. But that is changing as researchers recognize that consciousness can be broken down into pieces that can be tackled by the techniques of modern neurobiology. In particular, studies of the visual system are beginning to show how the neurons along the visual pathway come to represent what we actually perceive and not just what registers on the retina.</jats:p>

<jats:p>Brain research on mental illnesses has made substantial advances in recent years, supported by conceptual and technological developments in cognitive neuroscience. Brain-based cognitive models of illnesses such as schizophrenia and depression have been tested with a variety of techniques, including the lesion method, tract tracing, neuroimaging, animal modeling, single-cell recording, electrophysiology, neuropsychology, and experimental cognitive psychology. A relatively sophisticated picture is emerging that conceptualizes mental illnesses as disorders of mind arising in the brain. Convergent data using multiple neuroscience techniques indicate that the neural mechanisms of mental illnesses can be understood as dysfunctions in specific neural circuits and that their functions and dysfunctions can be influenced or altered by a variety of cognitive and pharmacological factors.</jats:p>

<jats:p>The capacity to predict future events permits a creature to detect, model, and manipulate the causal structure of its interactions with its environment. Behavioral experiments suggest that learning is driven by changes in the expectations about future salient events such as rewards and punishments. Physiological work has recently complemented these studies by identifying dopaminergic neurons in the primate whose fluctuating output apparently signals changes or errors in the predictions of future salient and rewarding events. Taken together, these findings can be understood through quantitative theories of adaptive optimizing control.</jats:p>

<jats:p>What kinds of knowledge underlie the use of language and how is this knowledge acquired? Linguists equate knowing a language with knowing a grammar. Classic “poverty of the stimulus” arguments suggest that grammar identification is an intractable inductive problem and that acquisition is possible only because children possess innate knowledge of grammatical structure. An alternative view is emerging from studies of statistical and probabilistic aspects of language, connectionist models, and the learning capacities of infants. This approach emphasizes continuity between how language is acquired and how it is used. It retains the idea that innate capacities constrain language learning, but calls into question whether they include knowledge of grammatical structure.</jats:p>

<jats:p>Can concepts from the theory of neural computation contribute to formal theories of the mind? Recent research has explored the implications of one principle of neural computation, optimization, for the theory of grammar. Optimization over symbolic linguistic structures provides the core of a new grammatical architecture, optimality theory. The proposition that grammaticality equals optimality sheds light on a wide range of phenomena, from the gulf between production and comprehension in child language, to language learnability, to the fundamental questions of linguistic theory: What is it that the grammars of all languages share, and how may they differ?</jats:p>

<jats:p>The ways in which actual measurements of sea-floor depth differ from average depths predicted by models of the solid Earth may provide useful information about how the planetary heat engine works. Actual depth is a function of plate tectonics and planetary heat flow. As S. Stein and C. Stein discuss in their Perspective, there is renewed interest in understanding these depth anomalies that is leading to improved models and extensive data sets.</jats:p>

<jats:p> In bacteria, transcription—the synthesis of RNA from DNA—is carried out by the enzyme RNA polymerase, which binds to the start site of a gene, the promoter. Now two reports in this week's issue, Wyman (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1658" related-article-type="in-this-issue" vol="275" xlink:href="10.1126/science.275.5306.1658" xlink:type="simple">1658</jats:related-article> ) and Miller (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1655" related-article-type="in-this-issue" vol="275" xlink:href="10.1126/science.275.5306.1655" xlink:type="simple">1655</jats:related-article> ), show two ways that this complex can be triggered to start transcription, both by proteins that act to change the configuration of the RNA polymerase enzyme itself. In his Perspective, Geiduschek discusses these and other examples of transcriptional regulation, suggesting that each may act on the step in the transcription process in which the RNA polymerase-promoter complex is reconfigured in preparation for RNA synthesis. </jats:p>

<jats:p> Two papers in the <jats:italic>Journal of Experimental Medicine</jats:italic> report the identification of a marker on the cell surface of T helper cells that can distinguish between the two main cell types, T <jats:sub>H</jats:sub> 1 and T <jats:sub>H</jats:sub> 2. This marker, the IL-12 receptor beta chain, will be useful for monitoring these important cell types, as well as providing a potential therapeutic target. </jats:p>