Is the WBE model appropriate for semi-arid shrubs subjected to clear cutting?

It is crucial to understand the adaptive mechanisms of woody plants facing periodic drought to assess their vulnerability to the increasing climate variability predicted in the Sahel. Guiera senegalensis J.F.Gmel is a semi-evergreen Combretaceae commonly found in Sahelian rangelands, fallows and crop fields because of its value as an agroforestry species. We compared canopy leafing, and allometric measurements of leaf area, stem area and stem length and their relationships with leaf water potential, stomatal conductance (gs) and soil-to-leaf hydraulic conductance (KS-L), in mature and current-year resprouts of G. senegalensis in Sahelian Niger. In mature shrubs, seasonal drought reduced the ratio of leaf area to cross-sectional stem area (AL : AS), mainly due to leaf shedding. The canopy of the current-year resprouts remained permanently leafed as the shrubs produced leaves and stems continuously, and their AL : AS ratio increased throughout the dry season. Their KS-L increased, whereas gs decreased. West, Brown and Enquist's (WBE) model can thus describe allometric trends in the seasonal life cycle of undisturbed mature shrubs, but not that of resprouts. Annual clear cutting drives allometric scaling relationships away from theoretical WBE predictions in the current-year resprouts, with scaling exponents 2.5 times greater than those of mature shrubs. High KS-L (twice that of mature shrubs) supports this intensive regeneration process. The adaptive strategy described here is probably common to many woody species that have to cope with both severe seasonal drought and regular disturbance over the long term.

A Procedure to Measure the in-Situ Hygrothermal Behavior of Earth Walls.

Rammed earth is a sustainable material with low embodied energy. However, its development as a building material requires a better evaluation of its moisture-thermal buffering abilities and its mechanical behavior. Both of these properties are known to strongly depend on the amount of water contained in wall pores and its evolution. Thus the aim of this paper is to present a procedure to measure this key parameter in rammed earth or cob walls by using two types of probes operating on the Time Domain Reflectometry (TDR) principle. A calibration procedure for the probes requiring solely four parameters is described. This calibration procedure is then used to monitor the hygrothermal behavior of a rammed earth wall (1.5 m × 1 m × 0.5 m), instrumented by six probes during its manufacture, and submitted to insulated, natural convection and forced convection conditions. These measurements underline the robustness of the calibration procedure over a large range of water content, even if the wall is submitted to quite important temperature variations. They also emphasize the importance of gravity on water content heterogeneity when the saturation is high, as well as the role of liquid-to-vapor phase change on the thermal behavior.

The influence of idiomatic salience during the comprehension of ambiguous idioms by patients with schizophrenia.

This study investigates whether figurative comprehension in schizophrenia is influenced by the salience of idiomatic meaning, and whether it is affected by clinical and demographic factors and IQ. Twenty-seven schizophrenic patients and 25 healthy participants performed a semantic relatedness judgement task which required the comprehension of idioms with two plausible meanings (literal and figurative). The study also used literal expressions. The figurative meaning of the idioms was less salient (ILS), more salient (IFS), or equally salient (IES) compared to the literal meaning. The results showed "a salience effect" (i.e., all participants understood the salient meanings better than the less salient meanings). There was also a "figurativeness effect" (i.e., healthy individuals understood the figurative meaning of IES better than the literal meaning but not schizophrenic patients). In patients, their thought disorder influenced the figurative comprehension of IFS. The verbal IQ influenced the figurative comprehension of ILS. The thought disorder, the verbal IQ, and the educational level influenced the figurative comprehension of IES. The patients' clinically evaluated concretism was associated with a reduced figurative comprehension of IFS and IES evaluated at a cognitive level. The results are discussed in relation to cognitive mechanisms which underscore figurative comprehension in schizophrenia.

N400 and P300 modulation as functions of processing level in schizophrenia patients exhibiting formal thought disorder.

In a semantic priming paradigm, the effects of different levels of processing on N400 were assessed by changing task demands in 10 schizophrenics and 10 matched controls. In the lexical decision task subjects had to discriminate between words and nonwords, and in the physical task subjects had to discriminate between cyan and blue ink letters. A lexicality test of reaction times demonstrated that the physical task was performed non-lexically in both groups. Moreover, a semantic priming reaction time effect was obtained only in the lexical decision task for the control group. The level of processing clearly affected event-related potentials. An N400 priming effect was only observed for the control group in the lexical decision task. By contrast, in the physical task a P300 effect was observed for either related or unrelated targets in both groups. Taken together, these results indicate that FTD schizophrenics are impaired specifically when task performance induces the semantic aspects of words as indexed by reduction of the N400 priming effect.

Left temporal impairment of auditory information processing in prematurely born 9-year-old children: an electrophysiological study.

Children born preterm more than average display cognitive difficulties that are significant enough to prevent normal schooling. The aim of our study was to provide better understanding of the long-term neuropathological processes associated with preterm injury, through the hypothesis that mild cognitive disorders might be related to slight deficits in primary functions such as attention and perception. Assessment of auditory pre-attentive processes was performed by recording the obligatory sensory response (N250) and the change-detection response (Mismatch Negativity, MMN). Topographic study of these responses was performed in fifteen 9-year-old children born preterm (27-33 weeks gestational age) matched to fifteen control children born at term. The auditory stimulus sequence consisted of 1000 Hz standard and 1100 Hz deviant tones (15%) delivered binaurally with an interstimulus interval of 700 ms. The results showed that MMN was similar in both groups. Analysis of the responses to standard repetitive tones demonstrated significantly smaller N250 wave amplitude in children born preterm. Scalp current density maps showed that this reduction in amplitude was associated with lower activity of both frontal and left supratemporal generators. Although the functional significance of the N250 wave in children remains to be clarified, our results indicate a disorder of auditory processes related to prematurity that might have consequences on the development of higher-level processes.

On understanding idiomatic language: The salience hypothesis assessed by ERPs.

Giora's [Giora, R., 1997. Understanding figurative and literal language: the Graded Salience Hypothesis. Cogn. Linguist. 7 (1), 183-206; Giora, R., 2003. On Our Mind: Salience Context and Figurative Language. Oxford Univ. Press, New York] Graded Salience Hypothesis states that more salient meanings-coded meanings foremost on our mind due to conventionality, frequency, familiarity, or prototypicality-are accessed faster than and reach sufficient levels of activation before less salient ones. This research addresses predictions derived from this model by examining the salience of familiar and predictable idioms, presented out of context. ERPs recorded from 30 subjects involved in reading and lexical decision tasks to (strongly/weakly) salient idioms and (figurative/literal) targets indicate that N400 amplitude was smaller for the last word of the strongly salient idioms than for the weakly salient idioms. Moreover, N400 amplitude of probes related to the salient meaning of strongly salient idioms was smaller than those of the 3 other conditions. In addition, response times to salient interpretations (the idiomatic meanings of highly salient idioms and the literal interpretations of less salient idioms) were shorter compared to the other conditions. These findings support Giora's Graded Salience Hypothesis. They show that salient meanings are accessed automatically, regardless of figurativity.

ERPs of metaphoric, literal, and incongruous semantic processing in schizophrenia.

The ability of schizophrenia patients to access metaphorical meaning was studied on the basis of psycholinguistic models of metaphor processing. ERPs were recorded from 20 schizophrenic and 20 control participants who were asked to read metaphorical, literal, and incongruous sentences and to judge their meaningfulness. In all participants, incongruous endings to sentences evoked the most negative N400 amplitude, whereas literal endings evoked more negative N400 amplitude than metaphorical ones, consistent with the direct model of metaphor processing. Although the patients had ERPs patterns that were similar to controls, they exhibited a more negative N400 amplitude for all sentences, LPC amplitude reduction, and latency delay in both components. The results suggest that schizophrenics have no specific anomalies in accessing the meaning of metaphors but are less efficient in integrating the semantic context of all sentences--both figurative and literal.

N400 anomalies in schizophrenia are correlated with the severity of formal thought disorder.

We explored the link between N400 anomalies and clinical profile in schizophrenia patients. N400 was recorded in 50 schizophrenia patients and 40 healthy controls during a lexical decision task with semantic priming. Comparison between controls and schizophrenia patients showed the classical anomalies reported for N400 in schizophrenia patients: greater amplitude for related words and lack of N400 effect. Analyses of the correlations between N400 effect and various symptoms of schizophrenia (formal thought disorder, positive symptoms, negative symptoms, overall symptoms, mean neuroleptic dose) or socioeducational data (age, vocabulary level, number of years of study) revealed that only the correlation with formal thought disorder was significant: the higher the scores for formal thought disorder, the lower the N400 effect observed.

An electrophysiologic study: can semantic context processes be mobilized in patients with thought-disordered schizophrenia?

OBJECTIVE: The aim of this study was to test the hypothesis that reinforcing the structuring of verbal material may bring about an improvement in contextualization processes in patients with formal thought-disordered schizophrenia. METHOD: A total of 38 schizophrenia patients with formal thought disorders and 24 matched healthy control subjects performed 2 lexical decision tasks, involving 2 levels of contextual structuring (with 16.7% and 33% of related words, respectively). The event-related potentials, N400 and late positive component (LPC), and behavioural variables (reaction times and error percentages) were analyzed. RESULTS: A context-structuring effect was observed on LPC, but not on N400. In subjects with schizophrenia, the N400 anomalies (that is, increase in amplitude for the related words and reduction of the N400 effect) persisted in both context-structuring conditions. Similarly, a reduction in LPC amplitude for the unrelated word category, as well as a decrease in the LPC effect, was observed in these patients. CONCLUSIONS: The schizophrenia patients with formal thought disorders did not benefit from the structuring of the context to implement context integration strategies. This deficit appears to be stable. The results are discussed within the framework of a previously published model of language comprehension.