There is a movement afoot in cognitive science to grant the body a central role in shaping the mind. Proponents of embodied cognition take as their theoretical starting point not a mind working on abstract problems, but a body that requires a mind to make it function. These opening lines by Clark (1998) are typical: "Biological brains are first and foremost the control systems for biological bodies. Biological bodies move and act in rich real-world surroundings" (p. 506).Traditionally, the various branches of cognitive science have viewed the mind as an abstract information processor, whose connections to the outside world were of little theoretical importance. Perceptual and motor systems, though reasonable objects of inquiry in their own right, were not considered relevant to understanding "central" cognitive processes. Instead, they were thought to serve merely as peripheral input and output devices. This stance was evident in the early decades of cognitive psychology, when most theories of human thinking dealt in propositional forms of knowledge. During the same time period, artificial intelligence was dominated by computer models of abstract symbol processing. Philosophy of mind, too, made its contribution to this zeitgeist, most notably in Fodor's (1983) modularity hypothesis. According to Fodor, central cognition is not modular, but its connections to the world are. Perceptual and motor processing are done by informationally encapsulated plug-ins providing sharply limited forms of input and output.However, there is a radically different stance that also has roots in diverse branches of cognitive science. This stance has emphasized sensory and motor functions,as well as their importance for successful interaction with the environment. Early sources include the view of 19th century psychologists that there was no such thing as "imageless thought" (Goodwin, 1999); motor theories of perception such as those suggested by William James and others (see Prinz, 1987, for a review); the developmental psychology of Jean Piaget, which emphasized the emergence of cognitive abilities out of a groundwork of sensorimotor abilities; and the ecological psychology of J. J. Gibson, which viewed perception in terms of affordances-potential interactions with the environment. In the 1980s, linguists began exploring how abstract concepts may be based on metaphors for bodily, physical concepts (e.g., Lakoff & Johnson, 1980). At the same time, within the field of artificial intelligence, behaviorbased robotics began to emphasize routines for interacting with the environment rather than internal representations used for abstract thought (see, e.g., Brooks, 1986).This kind of approach has recently attained high visibility, under the banner of embodied cognition. There is a growing commitment to the idea that the mind must be understood in the context of its relationship to a physical body that interacts with the world. It is argued that we have evolved from creatures whose neural resources were devoted primarily to perceptual and mo...

Perceiving other people's behaviors activates imitative motor plans in the perceiver, but there is disagreement as to the function of this activation. In contrast to other recent proposals (e.g., that it subserves overt imitation, identification and understanding of actions, or working memory), here it is argued that imitative motor activation feeds back into the perceptual processing of conspecifics' behaviors, generating top-down expectations and predictions of the unfolding action. Furthermore, this account incorporates recent ideas about emulators in the brain-mental simulations that run in parallel to the external events they simulate-to provide a mechanism by which motoric involvement could contribute to perception. Evidence from a variety of literatures is brought to bear to support this account of perceiving human body movement.

When humans talk without conventionalized arrangements, they engage in conversation--that is, a continuous and largely nonsimultaneous exchange in which speakers take turns. Turn-taking is ubiquitous in conversation and is the normal case against which alternatives, such as interruptions, are treated as violations that warrant repair. Furthermore, turn-taking involves highly coordinated timing, including a cyclic rise and fall in the probability of initiating speech during brief silences, and involves the notable rarity, especially in two-party conversations, of two speakers' breaking a silence at once. These phenomena, reported by conversation analysts, have been neglected by cognitive psychologists, and to date there has been no adequate cognitive explanation. Here, we propose that, during conversation, endogenous oscillators in the brains of the speaker and the listeners become mutually entrained, on the basis of the speaker's rate of syllable production. This entrained cyclic pattern governs the potential for initiating speech at any given instant for the speaker and also for the listeners (as potential next speakers). Furthermore, the readiness functions of the listeners are counterphased with that of the speaker, minimizing the likelihood of simultaneous starts by a listener and the previous speaker. This mutual entrainment continues for a brief period when the speech stream ceases, accounting for the cyclic property of silences. This model not only captures the timing phenomena observed inthe literature on conversation analysis, but also converges with findings from the literatures on phoneme timing, syllable organization, and interpersonal coordination.

Is the ability to entrain motor activity to a rhythmic auditory stimulus, that is "keep a beat," dependent on neural adaptations supporting vocal mimicry? That is the premise of the vocal learning and synchronization hypothesis, recently advanced to explain the basis of this behavior (A. Patel, 2006, Musical Rhythm, Linguistic Rhythm, and Human Evolution, Music Perception, 24, 99-104). Prior to the current study, only vocal mimics, including humans, cockatoos, and budgerigars, have been shown to be capable of motoric entrainment. Here we demonstrate that a less vocally flexible animal, a California sea lion (Zalophus californianus), can learn to entrain head bobbing to an auditory rhythm meeting three criteria: a behavioral response that does not reproduce the stimulus; performance transfer to a range of novel tempos; and entrainment to complex, musical stimuli. These findings show that the capacity for entrainment of movement to rhythmic sounds does not depend on a capacity for vocal mimicry, and may be more widespread in the animal kingdom than previously hypothesized.

The active acquisition of epigenetic changes is a poorly understood but important process in development, differentiation, and disease. Our work has shown that repression of the p16/pRb pathway in human epithelial cells, a condition common to stem cells and many tumor cells, induces dynamic epigenetic remodeling resulting in the targeted methylation of a selected group of CpG islands. We hypothesized that cells in this epigenetically plastic state could be programmed by the microenvironment to acquire epigenetic changes associated with tumorigenesis. Here, we describe an in vitro model system where epigenetically plastic cells were placed in an environment that induced epithelial to mesenchymal transition (EMT) and led to a program of acquired de novo DNA methylation at targeted sites. In this model, we found that repression of E-cadherin transcription preceded the subsequent acquisition of methylated CpG sites. Furthermore, the induction of EMT was accompanied by de novo methylation of several other gene promoters, including those of the estrogen receptor and Twist. These data demonstrate that signals from the microenvironment can induce phenotypic and gene expression changes associated with targeted de novo epigenetic alterations important in tumor progression, and that these alterations occur through a deterministic, rather than stochastic, mechanism. Given the dynamic epigenetic reprogramming that occurs in these cells, DNA methylation profiles observed in human tumors may reflect the history of environmental exposures during the genesis of a tumor.epigenetic remodeling ͉ human mammary epithelial cells ͉ microenvironment ͉ ras T he heritable regulation of gene expression changes that are critical to processes such as differentiation and disease can be controlled by epigenetic modifications of proteins and DNA sequences. We recently reported that the repression of p16 INK4A in primary human mammary epithelial cells (HMEC) activates an E2F-mediated increase in proteins that remodel chromatin and causes targeted de novo DNA methylation at a non-random collection of loci (1). These studies show that cells can acquire epigenetic plasticity by altering the p16/pRb pathway, and that this program of acquired de novo methylation has a deterministic (predictable) rather than stochastic (random) pattern. Furthermore, the coordinated set of de novo DNA methylation events are preceded by, and dependent upon, the repression of gene expression. Thus, during cancer progression, one may envision that tumor cells can acquire epigenetic plasticity through repression of the p16/pRb pathway via mutations, deletions, or methylation (2), which then provides the potential for programming epigenetic events. These observations are reminiscent of studies that show the acquisition of promoter hypermethylation upon modulation of estrogen or retinoic acid signaling (3, 4). In these cell population-based studies it is unclear whether the nonrandom hypermethylation events observed are due to induction or selection. To explore this question...