Functional magnetic resonance imaging (fMRI) was used to localize brain areas that were active during the observation of actions made by another individual. Object-and non-object-related actions made with different effectors (mouth, hand and foot) were presented. Observation of both object-and non-object-related actions determined a somatotopically organized activation of premotor cortex. The somatotopic pattern was similar to that of the classical motor cortex homunculus. During the observation of object-related actions, an activation, also somatotopically organized, was additionally found in the posterior parietal lobe. Thus, when individuals observe an action, an internal replica of that action is automatically generated in their premotor cortex. In the case of object-related actions, a further object-related analysis is performed in the parietal lobe, as if the subjects were indeed using those objects. These results bring the previous concept of an action observation/execution matching system (mirror system) into a broader perspective: this system is not restricted to the ventral premotor cortex, but involves several somatotopically organized motor circuits.

We use the concept of phase synchronization for the analysis of noisy nonstationary bivariate data. Phase synchronization is understood in a statistical sense as an existence of preferred values of the phase difference, and two techniques are proposed for a reliable detection of synchronous epochs. These methods are applied to magnetoencephalograms and records of muscle activity of a Parkinsonian patient. We reveal that the temporal evolution of the peripheral tremor rhythms directly reflects the time course of the synchronization of abnormal activity between cortical motor areas. [S0031-9007(98)07333-5] PACS numbers: 87.22.Jb, 05.45. + b, 87.22.As Irregular, nonstationary, and noisy bivariate data abound in many fields of research. Usually, two simultaneously registered time series are characterized by means of traditional cross-correlation (cross-spectrum) techniques or nonlinear statistical measures like mutual information or maximal correlation [1]. Only very recently a tool of nonlinear dynamics, mutual nonlinear prediction, was used for characterization of dynamical interdependence among systems [2]. In this Letter we use a synchronization approach to the analysis of such bivariate time series and introduce a new method to detect alternating epochs of phase locking from nonstationary data. By doing so we extract information on the interdependence of weakly interacting systems that cannot be obtained by traditional methods.Our technique, based on theoretical studies of phase synchronization of chaotic oscillators [3], can be fruitfully applied, e.g., in neuroscience, where synchronization processes are of crucial importance, e.g., for visual pattern recognition [4] and motor control [5]. Recent animal experiments have led to the conclusion that the control of coordinated movements is based on a synchronization of the firing activity of groups of neurons in the primary and in secondary motor areas [5]. Synchronization is also assumed to be involved in the generation of pathological movements, e.g., resting tremor in Parkinson's disease (PD) [6]. Although experimental studies indicate which parts of the nervous system are engaged in generating tremor activity, the dynamics of this process is not yet understood [7].Here we study synchronization between the activity of remote brain areas in humans by means of noninvasive measurements. This is possible because a group of synchronously firing neurons within a single area generates a magnetic field which can be registered outside the head by means of multichannel magnetoencephalography (MEG) [8]. Accordingly, synchronization of neuronal activity between remote areas is reflected as phase locking between MEG channels. Our analysis reveals phase synchronization (a) between the activity of certain brain areas and (b) between the activity of these areas and the muscle activity detected by electromyography (EMG).In particular, we find that the phase locking between the activity of primary and secondary motor areas is related to the coordination of antagonistic muscle...

No abstract

IntroductionGold has long been regarded as an "inert" surface and bulk gold surfaces do not chemisorb many molecules easily. However, in the last decade, largely through the efforts of Masatake Haruta, gold particles, particularly those below 5 nm in size, have begun to garner attention for unique catalytic properties (1-8). In recent years, supported gold particles have been shown to be effective as catalysts for low temperature CO oxidation (9), selective oxidation of propene to propene oxide (10), water gas shift (11), NO reduction (12), selective hydrogenation of acetylene (or butadiene) (13)

CO oxidation, although seemingly a simple chemical reaction, provides us with a panacea that reveals the richness and beauty of heterogeneous catalysis. The Fritz Haber Institute is a place where a multidisciplinary approach to study the course of such a heterogeneous reaction can be generated in house. Research at the institute is primarily curiosity driven, which is reflected in the five sections comprising this Review. We use an approach based on microscopic concepts to study the interaction of simple molecules with well-defined materials, such as clusters in the gas phase or solid surfaces. This approach often asks for the development of new methods, tools, and materials to prove them, and it is exactly this aspect, both, with respect to experiment and theory, that is a trade mark of our institute.

Ultrathin oxide films on metals offer new opportunities for the design of supported nanoclusters with potential use in catalysis. This requires a characterization at the atomistic level of the structure and composition of the thin film, of its morphology and defect structure. A proper selection of metal/oxide interface, film thickness, lattice mismatch, etc. makes it possible to prepare collections of supported metal particles with novel properties. This critical review describes some illustrative examples, emphasizes the role of the interplay between theory and experiment, and relates some recent findings related to the possibility to control the charge state of a supported nanoparticle on an ultrathin oxide film (211 references).

The arrangement of single gold and palladium atoms deposited on the surface of a 3 monolayer thin film of MgO was investigated using low-temperature scanning tunneling microscopy. While Pd atoms are arranged in a random fashion, Au forms an ordered array on the surface. The long-range ordering as well as the scanning tunneling microscopy appearance of single Au atoms on a 3 monolayer thin MgO film can be explained by partial charge transfer from the substrate to Au atoms as predicted recently by density functional theory calculations [Phys. Rev. Lett. 94, 226104 (2005)10.1103/PhysRevLett.94.226104]. In contrast with that, Au atoms on a thick film were found to be essentially neutral.

No abstract