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September 26, 2007; doi:10.1152/jn.00342.2007. Complex natural sounds (e.g., animal vocalizations or speech) can be characterized by specific spectrotemporal patterns the components of which change in both frequency (FM) and amplitude (AM). The neural coding of AM and FM has been widely studied in humans and animals but typically with either pure AM or pure FM stimuli. The neural mechanisms employed to perceptually unify AM and FM acoustic features remain unclear. Using stimuli with simultaneous sinusoidal AM (at rate f AM � 37 Hz) and FM (with varying rates ƒ FM), magnetoencephalography (MEG) is used to investigate the elicited auditory steady-state response (aSSR) at relevant frequencies (ƒ AM, ƒ FM, ƒ AM � f FM). Previous work demonstrated that for sounds with slower FM dynamics (f FM � 5 Hz), the phase of the aSSR at ƒ AM tracked the FM; in other words, AM and FM features were co-tracked and co-represented by “phase modulation ” encoding. This study

Our senses, indeed, by an effect almost mechanical, are passive to the impression of outside objects, whether agreeable or offensive; but the mind, possessed of a self-directing power, may turn its attention to whatever it thinks proper. Plutarch, Life of Pericles he word attention has had more varied usages than perhaps any other in psychology, all of which imply both intensive and selective aspects. Models of attention date back to Aristotle, who considered attention as a narrowing of the senses. 1 T All science is based on the attention paid to models and philosophies of thinking that drive scientific enquiry. And it is on the basis of what appears to be proven scientifically, that clinicians apply such information in clinical practice. The inner driving forces of attention are inherent in a genetic

The history of brain theory is described in terms of three kinds of theory of perception. The most widely used kind sees perception as dependent on passive inflow from the environment of information that is used to make and process representations of objects and events. A second kind views perception as an active search for information that is inherent in the environment and is extracted by tuned resonances in brain circuits. A third kind holds that perception works by the creation of information through chaotic dynamics by forming hypotheses about the environment, through which learning takes place. Experimental evidence for creative dynamics in brains is briefly sketched. The explanation is offered that brains, being finite systems, work this way in order to cope with the infinite complexity of the world. All that brains can know is the hypotheses they construct and the results of testing them by acting into the environment, and learning by assimilation from the sensory consequences of their actions. The process is described as intentionality. It works through the action-perception-assimilation cycle. The cost of this solution to the problem of infinite complexity by hypothesis testing is the progressive isolation of individuals, as they accumulate their unique experiences through which their personalities form. Socialization and the acquisition of shared knowledge requires the emergence of new personality structure by self-organization through chaotic dissolution of existing structure, as prelude to creation of new traits, habits and values. Dissolution works in a crisis situation by regression to earlier stages of development, from which a fresh start can be made. A state of malleability emerges in the depth of crisis, in which compassionate companions through lovin...

Semantics is the essence of human communication. It concerns the manufacture and use of symbols as representations to exchange meanings. Information technology is faced with the problem of using intelligent machines as intermediaries for interpersonal communication. The problem of designing such semantic machines has been intractable because brains and machines work on very different principles. A solution to the problem is to describe how brains create meaning and then express it in information by making a symbol as a representation to another brain in pairwise communication. Understanding of the neurodynamics by which brains create meaning may enable engineers to build devices with which they can communicate pairwise, as they do now with colleagues, though not with words, but with shared actions.