Lifetimes of states in 150Nd were measured using the recoil distance method following Coulomb excitation of 150Nd by a 132 MeV 32S beam. The experiment was performed at the Yale Tandem accelerator, employing the SPEEDY gamma-ray detector array and the New Yale Plunger Device. Reduced transition probabilities in 150Nd are compared to the predictions of the critical point symmetry X(5) of the phase/shape transition that occurs for the N = 90 rare earth isotones. Very good agreement was observed between the parameter-free (apart from scale) X(5) predictions and the low-spin level scheme of 150Nd, revealing this as the best case thus far for the realization of the X(5) symmetry.

In this letter, we calculate the redshift distribution of gamma-ray bursts assuming that they trace (i) the globally averaged star formation rate or (ii) the average metallicity in the Universe. While at redshifts 5 and below, both the star formation rate and metallicity are observationally determined modulo some uncertainties, at higher redshifts there are few constraints. We extrapolate the star formation rate and metallicity to higher redshifts and explore models that are broadly consistent with bounds on the optical depth from WMAP results. In addition, we also include parametric descriptions of the luminosity function, and the typical spectrum for GRBs. With these essential ingredients included in the modeling, we find that a substantial fraction 75% of GRBs are expected to originate at redshifts below 4, in variance with some previous estimates. Conversely, if we assume as expected for the collapsar model that gamma-ray bursts favour a low metallicity environment and therefore, relate the GRB rate to a simple model of the average metallicity as a function of redshift, we find that a higher fraction of bursts, about 40% originate from redshifts greater than 4. We conclude with the implications of SWIFT GRB detections.Comment: 5 pages, 2 figures, revised version, MNRAS pink pages in press, error in y-axis label in Fig.2 (bottom panel) correcte

Neurons recorded in behaving animals often do not discernibly respond to sensory input and are not overtly task-modulated. These non-classically responsive neurons are difficult to interpret and are typically neglected from analysis, confounding attempts to connect neural activity to perception and behavior. Here, we describe a trial-by-trial, spike-timing-based algorithm to reveal the coding capacities of these neurons in auditory and frontal cortex of behaving rats. Classically responsive and non-classically responsive cells contained significant information about sensory stimuli and behavioral decisions. Stimulus category was more accurately represented in frontal cortex than auditory cortex, via ensembles of non-classically responsive cells coordinating the behavioral meaning of spike timings on correct but not error trials. This unbiased approach allows the contribution of all recorded neurons – particularly those without obvious task-related, trial-averaged firing rate modulation – to be assessed for behavioral relevance on single trials.

Insanally MN, Albanna BF, Bao S. Pulsed noise experience disrupts complex sound representations. J Neurophysiol 103: 2611-2617, 2010. First published March 3, 2010 doi:10.1152/jn.00872.2009. Cortical sound representations are adapted to the acoustic environment. Early exposure to exponential frequency-modulated (FM) sweeps results in more neurons selective to the experienced sounds. Here we examined the influence of pulsed noise experience on the development of sound representations in the primary auditory cortex (AI) of the rat. In naïve animals, FM sweep direction selectivity depends on the characteristic frequency (CF) of the neuron-low CF neurons tend to select for upward sweeps and high CF neurons for downward sweeps. Such a CF dependence was not observed in animals that had received weeklong exposure to pulsed noise in periods from postnatal day 8 (P8) to P15 or from P24 to P39. In addition, AI tonotopicity, tuning bandwidth, intensity threshold, toneresponsiveness, and sweep response magnitude were differentially affected by the noise experience depending on the exposure time windows. These results are consistent with previous findings of feature-dependent multiple sensitive periods. The different effects induced here by pulsed noise and previously by FM sweeps further indicate that plasticity in cortical complex sound representations is specific to the sensory input. I N T R O D U C T I O NEarly experience has a significant influence on complex sound processing at both the behavioral and neuronal representational levels. Juvenile songbirds must hear tutor song early in life to accurately reproduce the learned song later in development (Marler and Peters 1982). Experience-dependent plasticity has been shown for the learning of the zebra finches' own song (Doupe and Solis 1997;Volman 1993).Electrophysiological studies show that neurons in the auditory forebrain of songbirds are selective for natural sounds (Grace et al. 2003;Margoliash 1986;Müller and Leppelsack 1985;Woolley et al. 2005), and such selectivity develops gradually (Amin et al. 2007). In addition to shaping perceptual behaviors, early experience also alters sensory neuronal representations (Brainard and Knudsen 1993;de Villers-Sidani et al. 2007Fagiolini et al. 1994;Han et al. 2007;Kim and Bao 2009;Merzenich et al. 1984;Polley et al. 2004;Simons and Land 1987;Takahashi et al. 2006; Van der Loos and Woolsey 1973;Wiesel and Hubel 1963;Zhang et al. 2001). In mammals, it has recently been shown that the maintenance and refinement of FM sweep selectivity are experience dependent (Razak et al. 2008). The development of complex sound features emerges in a series of sensitive periods within a monthlong critical period window. Early exposure to frequency-modulated (FM) sweeps alters frequency and bandwidth representations, and later exposure changes FM sweep selectivity (Insanally et al. 2009). This study did not, however, rule out the possibility that the observed effects were mainly caused by the broadband nature of the selected FM stimulus and not...

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