The application of rules in morphology, syntax and number processing: a case of selective deficit of procedural or executive mechanisms?: Deficit of procedural or executive mechanisms

International audienceDeclarative memory is a long-term store for facts, concepts and words. Procedural memory subserves the learning and control of sensorimotor and cognitive skills, including the mental grammar. In this study, we report a single-case study of a mild aphasic patient who showed procedural deficits in the presence of preserved declarative memory abilities. We administered several experiments to explore rule application in morphology, syntax and number processing. Results partly support the differentiation between declarative and procedural memory. Moreover, the patient's performance varied according to the domain in which rules were to be applied, which underlines the need for more fine-grained distinctions in cognition between procedural rules

Repeated attempts, phonetic errors, and syllabifications in a case study:Evidence of impaired transfer from phonology to articulatory planning

Background: In aphasia, impairments affecting stages after lexical access have been subdivided into three types: 1. impairments specifying a sequence of phonemes after lexical access (the reproduction variety of conduction aphasia, CA); 2. impairments holding on to these representations during articulatory planning (the short-term memory (STM) variety of CA); and 3. Impairments specifying integrated articulatory/motor plans for clusters of phonemes (apraxia of speech, AoS). Models of speech production, however, suggest more articulated possibilities (i.e., different subtypes of articulatory impairments). Aims: We investigated the impairment in a person with aphasia whose preliminary assessment revealed mixed speech characteristics, combining features typically used to identify CA – phonological errors across tasks and repeated attempts at the target – with features typically used to identify AoS – phonetic errors and word dysfluencies (phoneme elongations and syllabifications). Our preliminary hypothesis was that there was a difficulty transferring information from an (intact) phonological output buffer to articulatory planning. Slow/noisy transfer would predict dysfluencies, errors selecting motor programs, but also repeated attempts (RA) at revising the output in the face of intact feedback and intact original representations. This hypothesis also predicts effects of position and phonological complexity. Method and Procedure: We tested CS’s word and nonword repetition, word reading, and picture naming. We quantified lexical and non-lexical errors, repeated attempts, phonetic errors, and syllabifications. We assessed effects of word frequency, word length, phoneme position, and syllabic and phonological complexity. Results: CS made similar errors across tasks, consistent with a post-lexical impairment. His RAs most often built up a correct target from fragments and/or previously incorrect attempts, similar to a conduite d’approche. He also produced more errors in later positions, and more repeated attempts on longer words. However, inconsistent with decay from an output buffer, phonological errors did not increase with word length. Finally, frequency mattered, consistent with easier/faster access to simpler/more practiced motor plans. Conclusions: CS’s speech characteristics and anatomical lesion are consistent with transfer limitations between phonology and articulatory planning. However, CS has more difficulties in computing articulatory plans than in selecting and retaining phonological representations, as commonly attributed to CA. CS’s case suggests that different varieties of phonological and articulatory disorders need to be distinguished, beyond a strict dichotomy AoS/CA (e.g., involving transfer limitations and difficulties in computing, selecting,, and/or initiating articulatory plans)

Identification of Hyaloperonospora arabidopsidis Transcript Sequences Expressed during Infection Reveals Isolate-Specific Effectors

Biotrophic plant pathogens secrete effector proteins that are important for infection of the host. The aim of this study was to identify effectors of the downy mildew pathogen Hyaloperonospora arabidopsidis (Hpa) that are expressed during infection of its natural host Arabidopsis thaliana. Infection-related transcripts were identified from Expressed Sequence Tags (ESTs) derived from leaves of the susceptible Arabidopsis Ws eds1-1 mutant inoculated with the highly virulent Hpa isolate Waco9. Assembly of 6364 ESTs yielded 3729 unigenes, of which 2164 were Hpa-derived. From the translated Hpa unigenes, 198 predicted secreted proteins were identified. Of these, 75 were found to be Hpa-specific and six isolate Waco9-specific. Among 42 putative effectors identified there were three Elicitin-like proteins, 16 Cysteine-rich proteins and 18 host-translocated RXLR effectors. Sequencing of alleles in different Hpa isolates revealed that five RXLR genes show signatures of diversifying selection. Thus, EST analysis of Hpa-infected Arabidopsis is proving to be a powerful method for identifying pathogen effector candidates expressed during infection. Delivery of the Waco9-specific protein RXLR29 in planta revealed that this effector can suppress PAMP-triggered immunity and enhance disease susceptibility. We propose that differences in host colonization can be conditioned by isolate-specific effectors

Agroforesterie et services écosystémiques en zone tropicale

Respectueux de l’environnement et garantissant une sécurité alimentaire soutenue par la diversification des productions et des revenus qu’ils procurent, les systèmes agroforestiers apparaissent comme un modèle prometteur d’agriculture durable dans les pays du Sud les plus vulnérables aux changements globaux. Cependant, ces systèmes agroforestiers ne peuvent être optimisés qu’à condition de mieux comprendre et de mieux maîtriser les facteurs de leurs productions. L’ouvrage présente un ensemble de connaissances récentes sur les mécanismes biophysiques et socio-économiques qui sous-tendent le fonctionnement et la dynamique des systèmes agroforestiers. Il concerne, d’une part les systèmes agroforestiers à base de cultures pérennes, telles que cacaoyers et caféiers, de régions tropicales humides en Amérique du Sud, en Afrique de l’Est et du Centre, d’autre part les parcs arborés et arbustifs à base de cultures vivrières, principalement de céréales, de la région semi-aride subsaharienne d’Afrique de l’Ouest. Il synthétise les dernières avancées acquises grâce à plusieurs projets associant le Cirad, l’IRD et leurs partenaires du Sud qui ont été conduits entre 2012 et 2016 dans ces régions. L’ensemble de ces projets s’articulent autour des dynamiques des systèmes agroforestiers et des compromis entre les services de production et les autres services socio-écosystémiques que ces systèmes fournissent