Gamma oscillatory firing reveals distinct populations of pyramidal cells in the CA1 region of the hippocampus

Hippocampal place cells that fire together within the same cycle of theta oscillations represent the sequence of positions (movement trajectory) that a rat traverses on a linear track. Furthermore, it has been suggested that the encoding of these and other types of temporal memory sequences is organized by gamma oscillations nested within theta oscillations. Here, we examined whether gamma-related firing of place cells permits such discrete temporal coding. We found that gamma-modulated CA1 pyramidal cells separated into two classes on the basis of gamma firing phases during waking theta periods. These groups also differed in terms of their spike waveforms, firing rates, and burst firing tendency. During gamma oscillations one group's firing became restricted to theta phases associated with the highest gamma power. Consequently, on the linear track, cells in this group often failed to fire early in theta-phase precession (as the rat entered the place field) if gamma oscillations were present. The second group fired throughout the theta cycle during gamma oscillations, and maintained gamma-modulated firing at different stages of theta-phase precession. Our results suggest that the two different pyramidal cell classes may support different types of population codes within a theta cycle: one in which spike sequences representing movement trajectories occur across subsequent gamma cycles nested within each theta cycle, and another in which firing in synchronized gamma discharges without temporal sequences encode a representation of location. We propose that gamma oscillations during theta-phase precession organize the mnemonic recall of population patterns representing places and movement paths

RhPt/graphite catalysts for CO electrooxidation: Performance of mixed metal and alloyed surfaces

Cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS) have been used to characterise novel PtRh mixed metal and surface alloyed active phases supported on 5% Pt/graphite catalysts (5% Pt/G). The active phases could be prepared using forced deposition or a combination of forced deposition and thermal annealing in a flowing 5% hydrogen in argon gas mixture at 700 K. The protocols employed originate directly from previous single crystal studies of Rh on Pt{100} whereby Rh overlayers (either singly adsorbed or as a ‘sandwich structure’ of alternate Pt/Rh/Pt layers) could be transformed into surface PtRh alloys by careful thermal annealing. We demonstrate that this method is also successful for the preparation of active supported catalysts for CO electrooxidation whereby a peak potential as low as 0.60 V (Pd/H) for the CO oxidation is reported (0.12 V lower than that on 5% Pt/G). Moreover, the onset potential for CO stripping is lowered to 0.33 V (Pd/H). The presence of alloyed PtRh phases gives rise to a small but reproducible 0.1–0.2 eV shift to higher binding energy of the Pt 4f7/2 XPS peak together with strongly modified Pt and Rh electrosorption features in the CV which correlate with changes in surface composition. Unusual kinetic behaviour in the CO stripping peaks from the PtRh catalyst as a function of CO coverage is ascribed to competition between electrochemical oxide on Rh and CO-induced blocking of electrochemical oxide formation sites at the highest CO coverage. For PtRh alloys, the onset of electrochemical oxide formation shifts to more positive potentials relative to Rh overlayers and so a different behaviour towards CO electrooxidation is observed

Cracking the code of oscillatory activity

Neural oscillations are ubiquitous measurements of cognitive processes and dynamic routing and gating of information. The fundamental and so far unresolved problem for neuroscience remains to understand how oscillatory activity in the brain codes information for human cognition. In a biologically relevant cognitive task, we instructed six human observers to categorize facial expressions of emotion while we measured the observers' EEG. We combined state-of-the-art stimulus control with statistical information theory analysis to quantify how the three parameters of oscillations (i.e., power, phase, and frequency) code the visual information relevant for behavior in a cognitive task. We make three points: First, we demonstrate that phase codes considerably more information (2.4 times) relating to the cognitive task than power. Second, we show that the conjunction of power and phase coding reflects detailed visual features relevant for behavioral response-that is, features of facial expressions predicted by behavior. Third, we demonstrate, in analogy to communication technology, that oscillatory frequencies in the brain multiplex the coding of visual features, increasing coding capacity. Together, our findings about the fundamental coding properties of neural oscillations will redirect the research agenda in neuroscience by establishing the differential role of frequency, phase, and amplitude in coding behaviorally relevant information in the brai

Research trends in forensic science:A scientometric approach to analyze the content of the INTERPOL reviews

The use of forensic evidence has become indispensable in many countries and jurisdictions around the world, however the dissemination of research advancements does not necessarily directly or easily reach the forensic science community. Reports from the INTERPOL International Forensic Science Managers Symposium outline major areas that are of interest to forensic practitioners across the INTERPOL member countries. The information contained in the INTERPOL reports is extensive but can be challenging to process. The purpose of this research is to provide a comprehensive overview of the evolution of trends within the INTERPOL reports over an 18 year period. References relating to 10 evidence types retrieved from the 14th to 19th INTERPOL IFSMS reports (2004-2019) were processed and compared with data exports from the citation database Scopus covering the same evidence types. The results from this work are summarised by investigating the relationships between the 10 evidence types. To explore the outputs a user-friendly R-Shiny application was developed and is freely available at: https://uod.ac.uk/lrcfsinterpolreportsexplorer

The influence of ethylene and ethylene modulators on shoot organogenesis in tomato

[EN] The influence of ethylene and ethylene modulators on the in vitro organogenesis of tomato was studied using a highly regenerating accession of the wild tomato Solanum pennellii and an F1 plant resulting from a cross between Solanum pennellii and Solanum lycopersicum cv. Anl27, which is known to have a low regeneration frequency. Four ethylene-modulating compounds, each at four levels, were used, namely: cobalt chloride (CoCl 2), which inhibits the production of ethylene; AgNO 3 (SN), which inhibits ethylene action; and Ethephon and the precursor 1-aminocyclopropane-1-carboxylic acid (ACC), which both promote ethylene synthesis. Leaf explants of each genotype were incubated on shoot induction medium supplemented with each of these compounds at 0, 10 or 15 days following bud induction. The results obtained in our assays indicate that ethylene has a significant influence on tomato organogenesis. Concentrations of ethylene lower than the optimum (according to genotype) at the beginning of the culture may decrease the percentage of explants with buds (B), produce a delay in their appearance, or indeed inhibit bud formation. This was observed in S. pennellii and the F1 explants cultured on media with SN (5.8-58.0 ¿M) as well as in the F1 explants cultured on medium with 21.0 ¿M CoCl 2. The percentage of explants with shoots (R) and the mean number of shoots per explant with shoots (PR) also diminished in media that contained SN. Shoots isolated from these explants were less developed compared to those isolated from control explants. On the other hand, ethylene supplementation may contribute to enhancing shoot development. The number of isolable shoots from S. pennellii explants doubled in media with ACC (9.8-98.0 ¿M). Shoots isolated from explants treated with ethylene releasing compounds showed a higher number of nodes when ACC and Ethephon were added at 10 days (in F1 explants) or at 15 days (in S. pennellii) after the beginning of culture. Thus, the importance of studying not only the concentration but also the timing of the application of regulators when developing regeneration protocols has been made manifest. An excess of ethylene supplementation may produce an inhibitory effect, as was observed when using Ethephon (17.2-69.0 ¿M). These results show the involvement of ethylene in tomato organogenesis and lead us to believe that ethylene supplementation may contribute to enhancing regeneration and shoot development in tomato. © 2012 Springer Science+Business Media B.V.Carlos Trujillo has a predoctoral fellowship from the Spanish 'Ministerio de Educacion y Ciencia'. This work has been funded by Universitat Politecnica de Valencia (PAID 05-10). The technical assistance of N. Palacios and the revision of the manuscript's English by J. Bergen are gratefully acknowledged.Trujillo Moya, C.; Gisbert Domenech, MC. (2012). The influence of ethylene and ethylene modulators on shoot organogenesis in tomato. Plant Cell, Tissue and Organ Culture. 111(1):141-148. https://doi.org/10.1007/s11240-012-0168-zS1411481111Abeles FB, Morgan PW, Saltveit ME (1992) Ethylene in plant biology. Academic Press, San DiegoBhatia P, Ashwath N, Senaratna T, David M (2004) Tissue culture studies of tomato (Lycopersicon esculentum). Plant Cell Tiss Org Cult 78:1–21Bhatia P, Ashwath N, Midmore DJ (2005) Effects of genotype, explant orientation, and wounding on shoot regeneration in tomato. In Vitro Cell Dev Biol-Plant 41:457–464Biddington NL (1992) The Influence of ethylene in plant-tissue culture. Plant Growth Regul 11:173–187Brown DC, Thorpe TA (1995) Crop improvement through tissue culture. World J Microbiol Biotechnol 11(4):409–415Chraibi KMB, Latche A, Roustan JP, Fallot J (1991) Stimulation of shoot regeneration from cotyledons of Helianthus annuus by the ethylene inhibitors,silver and cobalt. Plant Cell Rep 10:204–207Devi R, Dhaliwal MS, Kaur A, Gosal SS (2008) Effect of growth regulators on in vitro morphogenic response of tomato. Indian J Biotechnol 7:526–530Dias LLC, Santa-Catarina C, Ribeiro DM, Barros RS, Floh EIS, Otoni WC (2009) Ethylene and polyamine production patterns during in vitro shoot organogenesis of two passion fruit species as affected by polyamines and their inhibitor. Plant Cell Tiss Org Cult 99:199–208Dimasi-Theriou K, Economou AS (1995) Ethylene enhances shoot formation in cultures of the peach rootstock GF-677 (Prunus persica × P. amygdalus). Plant Cell Rep 15:87–90Gisbert C, Arrillaga I, Roig LA, Moreno V (1999) Adquisition of a collection of Lycopersicon pennellii (Corr. D’Arcy) transgenic plants with uidA and nptII marker genes. J Hortic Sci Biotechnol 74:105–109Hughes KW (1981) In vitro ecology: exogenous factors affecting growth and morphogenesis in plant culture systems. Environ Exp Bot 21:281–288Huxter TJ, Thorpe TA, Reid DM (1981) Shoot initiation in light- and darkgrown tobacco callus: the role of ethylene. Physiol Plant 53:319–326Kumar PP, Lakshmanan P, Thorpe TA (1998) Regulation of morphogenesis in plant tissue culture by ethylene. In Vitro Cell Dev Biol Plant 34:94–103Lima JE, Benedito VA, Figueira A, Peres LEP (2009) Callus, shoot and hairy root formation in vitro as affected by the sensitivity to auxin and ethylene in tomato mutants. Plant Cell Rep 28:1169–1177Lu J, Vahala J, Pappinen A (2011) Involvement of ethylene in somatic embryogenesis in Scots pine (Pinus sylvestris L.). Plant Cell Tiss Org Cult 107:25–33Mohiuddin AKM, Chowdhury MKU, Abdullah ZC, Napis S (1997) Influence of silver nitrate (ethylene inhibitor) on cucumber in vitro shoot regeneration. Plant Cell Tiss Org Cult 51:75–78Moshkov IE, Novikova GV, Hall MA, George EF (2008) Plant Growth Regulators III: ethylene. In: George EF, Hall MA, Klerk G-JD (eds) Plant Propaga-tion by Tissue Culture, vol 1. 3rd edn. Springer, The Netherlands, pp 239–248Murashige T, Skoog F (1962) A revised medium for rapid growth and bioassays with tobacco tissue cultures. Physiol Plant 15:473–497Osman MG, Khalafalla MM (2010) Promotion of in vitro shoot formation from shoot tip of tomato (Lycopersicon esculentum Mill. cv. Omdurman) by ethylene inhibitors. Int J Curr Res 4:82–86Ptak A, El Tahchy A, Wyzgolik G, Henry M, Laurain-Mattar D (2010) Effects of ethylene on somatic embryogenesis and galantamine content in Leucojum aestivum L. cultures. Plant Cell Tiss Org Cult 102:61–67Pua EC, Sim GE, Chi GL, Kong LF (1996) Synergistic effects of ethylene inhibitors and putrescine on shoot regeneration from hypocotyl explants of Chinese radish (Raphanus sativus L. var. longipinnatus Bailey) in vitro. 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Dual coding with STDP in a spiking recurrent neural network model of the hippocampus.

The firing rate of single neurons in the mammalian hippocampus has been demonstrated to encode for a range of spatial and non-spatial stimuli. It has also been demonstrated that phase of firing, with respect to the theta oscillation that dominates the hippocampal EEG during stereotype learning behaviour, correlates with an animal's spatial location. These findings have led to the hypothesis that the hippocampus operates using a dual (rate and temporal) coding system. To investigate the phenomenon of dual coding in the hippocampus, we examine a spiking recurrent network model with theta coded neural dynamics and an STDP rule that mediates rate-coded Hebbian learning when pre- and post-synaptic firing is stochastic. We demonstrate that this plasticity rule can generate both symmetric and asymmetric connections between neurons that fire at concurrent or successive theta phase, respectively, and subsequently produce both pattern completion and sequence prediction from partial cues. This unifies previously disparate auto- and hetero-associative network models of hippocampal function and provides them with a firmer basis in modern neurobiology. Furthermore, the encoding and reactivation of activity in mutually exciting Hebbian cell assemblies demonstrated here is believed to represent a fundamental mechanism of cognitive processing in the brain

Kainate Receptor-Mediated Modulation of Hippocampal Fast Spiking Interneurons in a Rat Model of Schizophrenia

Kainate receptor (KAR) subunits are believed to be involved in abnormal GABAergic neurotransmission in the hippocampus (HIPP) in schizophrenia (SZ) and bipolar disorder. Postmortem studies have shown changes in the expression of the GluR5/6 subunits of KARs in the stratum oriens (SO) of sectors CA2/3, where the basolateral amygdala (BLA) sends a robust projection. Previous work using a rat model of SZ demonstrated that BLA activation leads to electrophysiological changes in fast-spiking interneurons in SO of CA2/3. The present study explores KAR modulation of interneurons in CA2/3 in response to BLA activation. Intrinsic firing properties of these interneurons through KAR-mediated activity were measured with patch-clamp recordings from rats that received 15 days of picrotoxin infusion into the BLA. Chronic BLA activation induced changes in the firing properties of CA2/3 interneurons associated with modifications in the function of KARs. Specifically, the responsiveness of these interneurons to activation of KARs was diminished in picrotoxin-treated rats, while the after-hyperpolarization (AHP) amplitude was increased. In addition, we tested blockers of KAR subunits which have been shown to have altered gene expression in SO sector CA2/3 of SZ subjects. The GluR5 antagonist UBP296 further decreased AP frequency and increased AHP amplitude in picrotoxin-treated rats. Application of the GluR6/7 antagonist NS102 suggested that activation of GluR6/7 KARs may be required to maintain the high firing rates in SO interneurons in the presence of KA. Moreover, the GluR6/7 KAR-mediated signaling may be suppressed in PICRO-treated rats. Our findings indicate that glutamatergic activity from the BLA may modulate the firing properties of CA2/3 interneurons through GluR5 and GluR6/7 KARs. These receptors are expressed in GABAergic interneurons and play a key role in the synchronization of gamma oscillations. Modulation of interneuronal activity through KARs in response to amygdala activation may lead to abnormal oscillatory rhythms reported in SZ subjects

Significance of Input Correlations in Striatal Function

The striatum is the main input station of the basal ganglia and is strongly associated with motor and cognitive functions. Anatomical evidence suggests that individual striatal neurons are unlikely to share their inputs from the cortex. Using a biologically realistic large-scale network model of striatum and cortico-striatal projections, we provide a functional interpretation of the special anatomical structure of these projections. Specifically, we show that weak pairwise correlation within the pool of inputs to individual striatal neurons enhances the saliency of signal representation in the striatum. By contrast, correlations among the input pools of different striatal neurons render the signal representation less distinct from background activity. We suggest that for the network architecture of the striatum, there is a preferred cortico-striatal input configuration for optimal signal representation. It is further enhanced by the low-rate asynchronous background activity in striatum, supported by the balance between feedforward and feedback inhibitions in the striatal network. Thus, an appropriate combination of rates and correlations in the striatal input sets the stage for action selection presumably implemented in the basal ganglia

Phonon Raman spectra of colloidal CdTe nanocrystals: effect of size, non-stoichiometry and ligand exchange

Resonant Raman study reveals the noticeable effect of the ligand exchange on the nanocrystal (NC) surface onto the phonon spectra of colloidal CdTe NC of different size and composition. The oleic acid ligand exchange for pyridine ones was found to change noticeably the position and width of the longitudinal optical (LO) phonon mode, as well as its intensity ratio to overtones. The broad shoulder above the LO peak frequency was enhanced and sharpened after pyridine treatment, as well as with decreasing NC size. The low-frequency mode around 100 cm-1 which is commonly related with the disorder-activated acoustical phonons appears in smaller NCs but is not enhanced after pyridine treatment. Surprisingly, the feature at low-frequency shoulder of the LO peak, commonly assigned to the surface optical phonon mode, was not sensitive to ligand exchange and concomitant close packing of the NCs. An increased structural disorder on the NC surface, strain and modified electron-phonon coupling is discussed as the possible reason of the observed changes in the phonon spectrum of ligand-exchanged CdTe NCs