Catarina Silva

Emotion processing in words: a test of the neural re-use hypothesis using surface and intracranial EEG

This study investigates the spatiotemporal brain dynamics of emotional information processing during reading using a combination of surface and intracranial electroencephalography (EEG). Two different theoretical views were opposed. According to the standard psycholinguistic perspective, emotional responses to words are generated within the reading network itself subsequent to semantic activation. According to the neural re-use perspective, brain regions that are involved in processing emotional information contained in other stimuli (faces, pictures, smells) might be in charge of the processing of emotional information in words as well. We focused on a specific emotion-disgust-which has a clear locus in the brain, the anterior insula. Surface EEG showed differences between disgust and neutral words as early as 200 ms. Source localization suggested a cortical generator of the emotion effect in the left anterior insula. These findings were corroborated through the intracranial recordings of two epileptic patients with depth electrodes in insular and orbitofrontal areas. Both electrodes showed effects of disgust in reading as early as 200 ms. The early emotion effect in a brain region (insula) that responds to specific emotions in a variety of situations and stimuli clearly challenges classic sequential theories of reading in favor of the neural re-use perspective.

Just another face in the crowd: evidence for decreased detection of angry faces in children with Williams syndrome.

The detection of social threat is crucial for adaptive behaviour. Previous studies have shown that angry faces capture attention and are processed more efficiently than happy faces. While this anger superiority effect has been found in typical and atypical development, it is unknown whether it exists in individuals with Williams syndrome (WS), who show reduced social fear and atypical sociability. In this study, children with WS searched for angry or happy target faces surrounded by 2, 5 or 8 distracters (happy or angry faces, respectively). Performance was compared to that of mental age-matched controls. Results revealed no group differences for happy faces, however for angry faces, the WS, but not the control group, showed a significant performance decrease for the 8-distracters condition, indicating the absence of an anger superiority effect, in good agreement with evidence for abnormal structure and function in brain areas for social threat processing in WS.

Structural Basis for the Oligomerization of the MADS Domain Transcription Factor SEPALLATA3 in Arabidopsis

The structure of the keratin-like domain of SEPALLATA3, a MADS transcription factor involved in floral organ development, was solved to 2.5 Å by x-ray crystallography. The structure shows a novel oligomerization interface formed by two alpha helices oriented approximately 90° apart. Dimerization occurs through interactions of helix 1, and tetramerization occurs through interactions of helix 2. In plants, MADS domain transcription factors act as central regulators of diverse developmental pathways. In Arabidopsis thaliana, one of the most central members of this family is SEPALLATA3 (SEP3), which is involved in many aspects of plant reproduction, including floral meristem and floral organ development. SEP3 has been shown to form homo and heterooligomeric complexes with other MADS domain transcription factors through its intervening (I) and keratin-like (K) domains. SEP3 function depends on its ability to form specific protein-protein complexes; however, the atomic level determinants of oligomerization are poorly understood. Here, we report the 2.5-Å crystal structure of a small portion of the intervening and the complete keratin-like domain of SEP3. The domains form two amphipathic alpha helices separated by a rigid kink, which prevents intramolecular association and presents separate dimerization and tetramerization interfaces comprising predominantly hydrophobic patches. Mutations to the tetramerization interface demonstrate the importance of highly conserved hydrophobic residues for tetramer stability. Atomic force microscopy was used to show SEP3-DNA interactions and the role of oligomerization in DNA binding and conformation. Based on these data, the oligomerization patterns of the larger family of MADS domain transcription factors can be predicted and manipulated based on the primary sequence.

Evolution of the Plant Reproduction Master Regulators LFY and the MADS Transcription Factors: The Role of Protein Structure in the Evolutionary Development of the Flower

Understanding the evolutionary leap from non-flowering (gymnosperms) to flowering (angiosperms) plants and the origin and vast diversification of the floral form has been one of the focuses of plant evolutionary developmental biology. The evolving diversity and increasing complexity of organisms is often due to relatively small changes in genes that direct development. These “developmental control genes” and the transcription factors (TFs) they encode, are at the origin of most morphological changes. TFs such as LEAFY (LFY) and the MADS-domain TFs act as central regulators in key developmental processes of plant reproduction including the floral transition in angiosperms and the specification of the male and female organs in both gymnosperms and angiosperms. In addition to advances in genome wide profiling and forward and reverse genetic screening, structural techniques are becoming important tools in unraveling TF function by providing atomic and molecular level information that was lacking in purely genetic approaches. Here, we summarize previous structural work and present additional biophysical and biochemical studies of the key master regulators of plant reproduction – LEAFY and the MADS-domain TFs SEPALLATA3 and AGAMOUS. We discuss the impact of structural biology on our understanding of the complex evolutionary process leading to the development of the bisexual flower.

Literacy: Exploring working memory systems

Previous research showed an important association between reading and writing skills (literacy) and the phonological loop. However, the effects of literacy on other working memory components remain unclear. In this study, we investigated performance of illiterate subjects and their matched literate controls on verbal and nonverbal working memory tasks. Results revealed that the phonological loop is significantly influenced by literacy, while the visuospatial sketchpad appears to be less affected or not at all. Results also suggest that the central executive might be influenced by literacy, possibly as an expression of cognitive reserve.

Just another social scene: evidence for decreased attention to negative social scenes in high-functioning autism.

The adaptive threat-detection advantage takes the form of a preferential orienting of attention to threatening scenes. In this study, we compared attention to social scenes in 15 high-functioning individuals with autism (ASD) and matched typically developing (TD) individuals. Eye-tracking was recorded while participants were presented with pairs of scenes, either emotional positive-neutral, emotional negative-neutral or neutral–neutral scenes. Early allocation of attention, the first image fixated in each pair, differed between groups: contrary to TD individuals who showed the typical threat-detection advantage towards negative images, the ASD group failed to show a bias toward threat-related scenes. Later processing of stimuli, indicated by the total fixation to the images during the 3-s presentation, was found unaffected in the ASD group. These results support the hypothesis of an early atypical allocation of attention towards natural social scenes in ASD, that is compensated in later stages of visual processing.

Attachment insecurity and strategies for regulation: When emotion triggers attention

Attachment-related strategies are thought to be critical for regulation and processing of emotional information. This study examined biases in selective attention to emotional stimuli as a function of insecure attachment. Participants searched for a single target image preceded by to-be-ignored distracters depicting emotional images varying in valence and arousal. Results revealed that, in general, negative distracters affected accuracy levels, and that the anxious attached participants showed a clear interference of the emotional distracters. In contrast, the avoidant group evinced a higher control on such interference. In addition, arousal ratings to distracter images indicated superior emotional activation only for anxious attached participants. Consistent with the evolutionary-based attachment theory threat-related stimuli prompted priority attentional responses. Present findings are in line with evidence showing the deployment of distinct strategies in insecurely attached individuals for the regulation of attention to emotional information.

Merging of synchrotron serial crystallographic data by a genetic algorithm

A genetic algorithm is described and used to select which sub-data sets from a larger pool can be merged into a high-quality data set.

Tetramerization of MADS family transcription factors SEPALLATA3 and AGAMOUS is required for floral meristem determinacy in Arabidopsis

Abstract The MADS transcription factors (TF) constitute an ancient family of TF found in all eukaryotes that bind DNA as obligate dimers. Plants have dramatically expanded the functional diversity of the MADS family during evolution by adding protein–protein interaction domains to the core DNA-binding domain, allowing the formation of heterotetrameric complexes. Tetramerization of plant MADS TFs is believed to play a central role in the evolution of higher plants by acting as one of the main determinants of flower formation and floral organ specification. The MADS TF, SEPALLATA3 (SEP3), functions as a central protein–protein interaction hub, driving tetramerization with other MADS TFs. Here, we use a SEP3 splice variant, SEP3Δtet, which has dramatically abrogated tetramerization capacity to decouple SEP3 tetramerization and DNA-binding activities. We unexpectedly demonstrate that SEP3 heterotetramer formation is required for correct termination of the floral meristem, but plays a lesser role in floral organogenesis. The heterotetramer formed by SEP3 and the MADS protein, AGAMOUS, is necessary to activate two target genes, KNUCKLES and CRABSCLAW, which are required for meristem determinacy. These studies reveal unique and highly specific roles of tetramerization in flower development and suggest tetramerization may be required to activate only a subset of target genes in closed chromatin regions.

Chemical Composition of the Essential Oil from Annona crassiflora

Annona crassiflora is a species native to the cerrado region but also found in other regions of Brazil. The species belongs to the family of Annonaceae and their fruit is popularly known as araticum, ariticum, and marolo [1]. The species is used in folk medicine in the treatment of wounds and snakebites, and as an antimicrobial and antidiarrheal [2]. Some studies have shown that this species has antioxidant and cytotoxic activity [3, 4]. The objective of this study was to determine the chemical composition of the essential oil from different parts at different times of A. crassiflora collected in southern Brazil. The leaves, fruits, and flowers of A. crassiflora were collected in the town of Tres Rios, Brazil in 2010. A voucher specimen (SMDB 12.938) has been deposited in the Herbarium of the UFSM. The fresh leaves were submitted to hydrodistillation (4 h) to yield ca. 0.3% of oil. The oil was submitted to GC analysis in a Shimadzu (GCMS-QP2010 Plus) instrument equipped with a capillary fused silica column (30 m 0.25 m) coated with RTx-5MS. The injector and detector temperatures were 240 and 260 C, respectively. He was used as carrier gas at a flow rate of 1 mL min–1, injection was in the split mode (1:10), and the injection volume was 1 mg mL–1 of a solution containing withdraw oil in hexane. MS spectra were obtained using electron impact at 70 eV with a scan interval of 2.94 scan s–1. Compound identification was based on the comparison of retention indexes with the same columns and mass spectra described [5, 6]. Retention indices (RI) were obtained according to the method of Van den Dool relative to C7–C30 saturated n-alkanes standard. Quantitative analyses of the chemical constituents was performed using a flame ionization detector (FID) using a Shimadzu (GC-2010) instrument under the same conditions and with the same column as reported for the GC-MS. Table 1 lists the essential oils of the compounds obtained from A. crassiflora. Twenty-five compounds were identified, representing 94.0% of the oils. The essential oil of A. crassiflora consists mainly of oxygenated sesquiterpenes. Nerolidol was found in the highest concentration in all the oils analyzed. The oil from the leaves collected in summer showed a higher concentration of nerolidol (57.1%), and the oil of the fruit collected in summer showed the lowest concentration (18.7%). The essential oil obtained from the fruit showed no sesquiterpene hydrocarbons. Octanol acetate, epi-longipinalol, spathulenol, and dihydromyrcene comprises the majority of the fruit essential oil. The leaves collected in the spring contained spathulenol and caryophyllene oxide as major compounds. The oils collected from leaves (summer and autumn) show -elemene and -caryophyllene in higher concentrations than other oils, and -caryophyllene was found in the leaves in these two seasons.