Refinement of neuronal synchronization with gamma oscillations in the medial prefrontal cortex after adolescence

The marked anatomical and functional changes taking place in the medial prefrontal cortex (PFC) during adolescence set grounds for the high incidence of neuropsychiatric disorders with adolescent onset. Although circuit refinement through synapse pruning may constitute the anatomical basis for the cognitive differences reported between adolescents and adults, a physiological correlate of circuit refinement at the level of neuronal ensembles has not been demonstrated. We have recorded neuronal activity together with local field potentials in the medial PFC of juvenile and adult mice under anesthesia, which allowed studying local functional connectivity without behavioral or sensorial interference. Entrainment of pyramidal neurons and interneurons to gamma oscillations, but not to theta or beta oscillations, was reduced after adolescence. Interneurons were synchronized to gamma oscillations across a wider area of the PFC than pyramidal neurons, and the span of interneuron synchronization was shorter in adults than juvenile mice. Thus, transition from childhood to adulthood is characterized by reduction of the strength and span of neuronal synchronization specific to gamma oscillations in the mPFC. The more restricted and weak ongoing synchronization in adults may allow a more dynamic rearrangement of neuronal ensembles during behavior and promote parallel processing of information.Fil: de Almeida, Julián. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Ciencias Fisiológicas. Laboratorio de Fisiología de Circuitos Neuronales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Jourdan, Iván. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Ciencias Fisiológicas. Laboratorio de Fisiología de Circuitos Neuronales; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería; ArgentinaFil: Murer, Mario Gustavo. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Ciencias Fisiológicas. Laboratorio de Fisiología de Circuitos Neuronales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Belforte, Juan Emilio. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Ciencias Fisiológicas; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Ciencias Fisiológicas. Laboratorio de Fisiología de Circuitos Neuronales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Monitoreo de servicios ecosistémicos en un observatorio de cafetales agroforestales. Recomendaciones para el sector cafetalero

Ocho años de estudio de la ecofisiología del café, a través de experimentación y de modelación y el monitoreo de los servicios del ecosistema (SE) en una gran finca cafetalera en Costa Rica, revelaron varias recomendaciones prácticas para los agricultores y los formuladores de políticas. El sistema de cultivo estudiado dentro de nuestro observatorio colaborativo (Coffee-Flux), corresponde a un sistema agroforestal (SAF) a base de café bajo la sombra de grandes árboles de Erythrina poeppigiana (16% de la cubierta del dosel). Una gran cantidad de SE y limitantes dependen de las propiedades locales del suelo (en este caso Andisoles), especialmente de la erosión/infiltración, el agua/carbono y la capacidad de almacenamiento de nutrientes. Por lo tanto, para la evaluación de SE, el tipo de suelo es crucial. Una densidad adecuada de árboles de sombra (bastante baja aquí por la condición de libre crecimiento), redujo la severidad de las enfermedades de las hojas con la posibilidad de reducir el uso de plaguicidas y fungicidas. Un inventario simple del área basal en el collar de las plantas de café permitió estimar la biomasa subterránea y la edad promedio de la plantación, para juzgar su valor de mercado y decidir cuándo reemplazarla. Las fincas de café probablemente estén mucho más cerca de la neutralidad de C que lo indicado en el protocolo actual de C-neutralidad, que solo considera árboles de sombra, no los cafetos ni el suelo. Se proponen evaluaciones más completas, que ncluyen árboles, café, hojarasca, suelo y raíces en el balance C del SAF. Los árboles de sombra ofrecen muchos SE si se gestionan adecuadamente en el contexto local. En comparación con las condiciones a pleno sol, los árboles de sombra pueden (i) reducir la erosión laminar en un factor de 2; (ii) aumentar la fijación de N y el % de N reciclado en el sistema, reduciendo así los requisitos de fertilizantes; (iii) reducir la severidad de enfermedades de las hojas; (iv) aumentar el secuestro de C; (v) mejorar el microclima y (vi) reducir sustancialmente los efectos del cambio climático. En nuestro estudio de caso, no se encontró ningún efecto negativo sobre el rendimiento del café

Tree fine roots dynamics and carbon sequestration potential in a Mediterranean agroforestry system

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Recording of mPFC activity under different global brain states.

<p><b>A.</b> Positioning of a multichannel recording “silicon probe” in the medial PFC (left) and of bipolar electrodes in the frontal cortex (cortical EEG) and hippocampus (hippocampal EEG, right). <b>B.</b> Representative example showing the cortical and hippocampal EEG patterns seen in mice under urethane anesthesia, the mirror changes in relative power taking place in a low frequency band recorded from the frontal cortex (purple trace) and the theta band recorded from the hippocampus (light blue), and the epochs selected automatically by the algorithm used to classify the global brain states (green and grey). <b>C.</b> Representative recording during a transition from the slow wave state (box) to the desynchronized state. Note at right the lower amplitude and higher frequency of the cortical EEG accompanied with theta activity in the hippocampus, which are characteristic of the desynchronized state. The two lower traces show activity in one channel of the silicon probe after being bandpass filtered to separate multiunit activity (MUA) and the local field potential (LFP).</p

Juvenile and adult mice show similar global brain states under urethane anesthesia.

<p>Relative power spectra corresponding to cortical (<b>A</b>) and hippocampal EEG (<b>B</b>), in juvenile and adult mice, in slow wave and desynchronized states. The data are the relative power encompassed between the 95% confidence intervals of the mean. Juveniles and adults show similar frequency composition of cortical and hippocampal EEG, but hippocampal theta shows a slightly higher frequency in adults (4.33±0.07 vs. 4.67±0.08 Hz; p<0.01, t-test).</p

Selective reduction of gamma entrainment of mPFC neurons during adolescence.

<p>The strength of synchronization between spikes and LFP in the mPFC was assessed by computing the resultant vector of circular distributions as shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0062978#pone-0062978-g003" target="_blank">Figure 3</a>. Entrainment magnitude refers to the average vector length ± SEM across units. In <b>A</b>, all spikes in each mPFC recording site (95 sites in juveniles, 98 sites in adults) were used to compute the circular distributions (multiunit activity). <b>B</b> shows the average vector length for all well sorted pyramidal neurons (32 in juvenile and 35 in adult mice), and <b>C</b> shows average vector length for all well isolated interneurons (25 in juvenile and 38 in adult mice). Statistical analysis showed significant interaction between age and oscillatory band in all cases, repeated measures ANOVA interaction: MUA F_4,764 = 21.0 p<0.0001, pyramidal cells F_4,260 = 4.37 p<0.005, interneurons F_4,244 = 2.47 p<0.05; *p<0.05; ***p<0.001 juvenile vs. adult Newman-Keuls post hoc test.</p

Neurons synchronize preferentially to gamma activity in the mPFC.

<p><b>A.</b> Representative traces showing the raw multiunit activity (MUA) and local field potential (LFP) recorded through one contact of a silicon probe located in the mPFC of an adolescent mouse. The traces shown below show signals resulting from band-pass digital filtering the LFP for alpha and high gamma bands. The green and red dots mark the occurrence of spikes from a pyramidal neuron sorted from MUA. Note the preferential occurrence of spikes in the troughs of the gamma oscillation. <b>B.</b> Spike-phase plots (bin size 10°) showing a uniform distribution of spikes across phases for the alpha band and a markedly non-uniform distribution for the same spikes across phases for the gamma band (statistically evaluated by the Rayleigh test). The plots correspond to the neuron shown in A. The resultant vector of the distribution has an angle (locking phase) and a length or module (locking strength). The numbers at the upper right quadrant of the plots refer to the radial axes of frequency distribution and vector length.</p

Reduced span of interneuron entrainment to gamma oscillations in adults.

<p><b>A.</b> Schematic representation showing the localization of recording sites in the mPFC. A coronal section of a representative animal was photographed under transmitted light and epifluorescence to show the location of fluorescent material left by the labeled silicon probe in the mPFC. To estimate the span of neuronal synchronization to gamma oscillations, we took the spikes of a given recording site and computed their spike-phase circular distribution for the LFP in the recording site from which they were recorded and for LFPs at other recording sites along the electrode. In this example, three circular distributions are depicted for one unit, representing the entrainment with the local LFP (cero distance) and LFPs obtained 100 and 400 µm apart. <b>B</b> and <b>C.</b> Entrainment strength to high-gamma oscillations as function of distance along the mPFC, for pyramidal neurons (<b>B</b>) and interneurons (<b>C</b>). In adults, interneuron entrainment to high gamma is more spatially restricted than in juveniles. * p<0.05 Newman-Keuls post hoc test after a two way ANOVA for repeated measures with significant interaction. Note that pyramidal neurons show a very local entrainment to gamma, whereas interneurons are coupled to gamma recorded 200 µm apart. Entrainment magnitude refers to the average vector length ± SEM at each LFP recording site along the mPFC.</p

Data from: Root community traits along a land use gradient: evidence of a community-level economics spectrum

1. There is a fundamental trade-off between leaf traits associated with either resource acquisition or resource conservation. This gradient of trait variation, called the economics spectrum also applies to fine roots but whether it is consistent for coarse roots or at the plant community level remains untested. 2. We measured a set of morphological and chemical root traits at a community level (functional parameters; FP) in 20 plant communities located along land-use intensity gradients and across 3 climatic zones (Tropical, Mediterranean and Montane). We hypothesized (i) the existence of a root economics spectrum in plant communities consistent within root types (fine, < 2 mm; coarse, 2-5 mm) but that ii) variations in root traits occur with soil depths (top 20 cm of soil and 100-150 cm deep) and iii) along land use gradients thus leading to variation in root FP. 3. Root FP co-varied, in line with the resource acquisition-conservation trade-off, from communities with root FP syndromes associated to resource acquisition (e.g. high specific root length, SRL; thin diameters and low root dry matter contents, RDMC) to root FP syndromes associated with resource conservation (e.g. low SRL, thick diameters and high RDMC). This pattern was consistent for both fine and coarse roots indicating a strong consistency of a trade-off between resource acquisition and conservation for plant roots. 4. Roots had different suites of traits at different depths, suggesting a disparity in root function and exploitation capacities. Shallow, fine roots were thinner, richer in nitrogen and with lower lignin concentrations associated to greater exploitation capacities compared to deep, fine roots. However, shallow coarse roots were richer in nitrogen, carbon and soluble concentrations than deep, coarse roots. 5. Fine root parameters of highly disturbed, herbaceous dominated plant communities in poorer soils were associated to foraging strategies, i.e. greater SRL and lower lignin and RDMC than those from less disturbed communities. Coarse roots however, were less sensitive to the land use gradient. 6. Synthesis This study demonstrates the existence of a general trade-off in root construction at a community level, which operates within all root types suggesting that all plant tissues are controlled by the trade-off between resource acquisition and conservation

Prieto_etal_2014_Data_mean and SE

Mean values and standard error for the functional parameters analysed in this study. For trait abbreviations please refer to the original publication. Details on climate, site and land use type descriptions are given in the publication and in the supplementary material; n=3 for Dm, RDMC and SRL; n=4 for RNC, RCC, Soluble, Cellulose and Ligni