Summer-drought constrains the phenology and growth of two coexisting Mediterranean oaks with contrasting leaf habit: implications for their persistence and reproduction

13 páginas, 9 figuras, 5 tablas.-- El PDF es la versión post-print.This study analyses how coexisting evergreen and deciduous oaks adjust their phenology to cope with the stressful Mediterranean summer conditions. We test the hypothesis that the vegetative and reproductive growth of the winter deciduous (Quercus faginea Lam.) is more affected by summer drought than that of the evergreen [Quercus ilex L. subsp. ballota (Desf.) Samp.]. First, we assessed the complete aboveground phenology of both species during two consecutive years. Shoot and litter production and bud, acorn and secondary growth were monitored monthly. Second, we identified several parameters affected by summer conditions: apical bud size, individual leaf area (LA), leaf mass per area (LMA) and acorn yield in both species, and leaf-fall in Q. faginea; and analysed their variation over 10 years. Q. ilex performed up to 25% of shoot growth and most leaf development during summer, whereas Q. faginea completed most of both phenophases during spring. Secondary growth was arrested in summer under drought conditions. Approximately, 30–40% of bud and 40–50% of acorn growth was undertaken during summer in both species. Summer drought related to differences in LA, LMA and leaf senescence, but not to acorn yield. Both species had similar year-to-year patterns of acorn production, though yields were always lower in Q. faginea. Bud size decreased severely in both species during extremely dry years. In Q. ilex, bud size tended to alternate between years of large and small buds, and these patterns were followed by opposite trends in stem length. In Q. faginea, bud size was more stable through time. Q. ilex was more phenologically active during summer than Q. faginea, indicating a higher tolerance to drought. Furthermore, bud and fruit growth (the only two phenophases that both species performed during summer) were more severely affected by summer drought in Q. faginea than in the evergreen. The differential effects of summer drought on key phenophases for the persistence (bud growth) and colonization ability (fruit production) of both species may have consequences for their coexistence.This study was possible thanks to the collaboration within the GLOBIMED network (Ministerio de Educación y Ciencia, Spain) and it was supported by the MEC-CICyT projects AGF96-0399, CGL2007-66066-C04/BOS and CGL2008- 04847-C02-01, DGA projects P-038/96 and GA-LC-011/2008, and INIA projects RTA2005-00100-C02-00 and SUM2006-00025-00-00. JJC acknowledges the support of the ‘‘Fundación Aragón I+D’’. SP and RM were funded by MEC by a postdoc (SEUI-FECYT) and a Juan de la Cierva contract, respectively. JA was funded by DGA.Peer reviewe

Performance in Sound-Symbol Learning Predicts Reading Performance 3 Years Later

To master the task of reading, children need to acquire a coding system representing speech as a sequence of visual symbols. Recent research suggested that performance in the processing of artificial script that relies on the association of sound and symbol may be associated with reading skill. The current longitudinal study examined the predictive value of a preschool sound-symbol paradigm (SSP) of reading performance 3 years later. The Morse-like SSP, IQ, and letter knowledge (LK) was assessed in young preschool children. Reading outcome measures were examined 3 years later. Word reading, pseudoword reading, and reading comprehension were predicted with age, IQ, LK, and SSP. The results showed that SSP substantially predicted reading fluency and reading comprehension 3 years later. For reading fluency measures, the influence of further predictor variables was not significant and SSP served as a sole predictor. Reading comprehension was best explained by SSP and age. The amount of variance SSP explained in reading 3 years later was remarkably high, with an explained variance between 63 and 82%, depending on the outcome reading variable. SSP turned out to be a substantial predictor of later reading performance in a language with statistically reliable spelling-to-sound relations. As LK is highly dependent on educational support, we assume that children in our socioeconomically diverse sample did not have much opportunity to acquire LK in their home environment. In contrast, the SSP challenges students to acquire new spelling-to-sound relations, simulating a core aspect of natural reading acquisition. Future work will test this paradigm in less transparent languages like English and explore its potential as a future standard assessment in the study of early reading development

Brain-to-brain synchrony in parent-child dyads and the relationship with emotion regulation revealed by fNIRS-based hyperscanning

Parent-child synchrony, the coupling of behavioral and biological signals during social contact, may fine-tune the child's brain circuitries associated with emotional bond formation and the child's development of emotion regulation. Here, we examined the neurobiological underpinnings of these processes by measuring parent's and child's prefrontal neural activity concurrently with functional near-infrared spectroscopy hyperscanning. Each child played both a cooperative and a competitive game with the parent, mostly the mother, as well as an adult stranger. During cooperation, parent's and child's brain activities synchronized in the dorsolateral prefrontal and frontopolar cortex (FPC), which was predictive for their cooperative performance in subsequent trials. No significant brain-to-brain synchrony was observed in the conditions parent-child competition, stranger-child cooperation and stranger-child competition. Furthermore, parent-child compared to stranger-child brain-to-brain synchrony during cooperation in the FPC mediated the association between the parent's and the child's emotion regulation, as assessed by questionnaires. Thus, we conclude that brain-to-brain synchrony may represent an underlying neural mechanism of the emotional connection between parent and child, which is linked to the child's development of adaptive emotion regulation. Future studies may uncover whether brain-to-brain synchrony can serve as a neurobiological marker of the dyad's socio-emotional interaction, which is sensitive to risk conditions, and can be modified by interventions

Sustained Selective Attention to Competing Amplitude-Modulations in Human Auditory Cortex

Auditory selective attention plays an essential role for identifying sounds of interest in a scene, but the neural underpinnings are still incompletely understood. Recent findings demonstrate that neural activity that is time-locked to a particular amplitude-modulation (AM) is enhanced in the auditory cortex when the modulated stream of sounds is selectively attended to under sensory competition with other streams. However, the target sounds used in the previous studies differed not only in their AM, but also in other sound features, such as carrier frequency or location. Thus, it remains uncertain whether the observed enhancements reflect AM-selective attention. The present study aims at dissociating the effect of AM frequency on response enhancement in auditory cortex by using an ongoing auditory stimulus that contains two competing targets differing exclusively in their AM frequency. Electroencephalography results showed a sustained response enhancement for auditory attention compared to visual attention, but not for AM-selective attention (attended AM frequency vs. ignored AM frequency). In contrast, the response to the ignored AM frequency was enhanced, although a brief trend toward response enhancement occurred during the initial 15 s. Together with the previous findings, these observations indicate that selective enhancement of attended AMs in auditory cortex is adaptive under sustained AM-selective attention. This finding has implications for our understanding of cortical mechanisms for feature-based attentional gain control

Development of Behavior Problems in Children with and without Specific Learning Disorders in Reading and Spelling from Kindergarten to Fifth Grade

Horbach J, Mayer A, Scharke W, Heim S, Günther T. Development of Behavior Problems in Children with and without Specific Learning Disorders in Reading and Spelling from Kindergarten to Fifth Grade. Scientific Studies of Reading. 2020;24(1):57-71.Previous studies have established the relationship between behavioral problems and specific learning disorders (SLD); however, the exact mechanism by which behavioral disorders impact SLD remains unclear. This longitudinal study used the Child Behavior Checklist (CBCL) to investigate how parents’ judgment of children’s behavioral problems changed from kindergarten to fifth grade in children diagnosed with or without specific learning disorders in reading and spelling (SLDrs) (N = 196). Growth component model analyses showed differential development of behavior problems between children with and without SLDrs. The groups did not differ before school entrance in externalizing behavior, internalizing behavior or any sub-scale of the CBCL. Parents reported their children with SLDrs as having higher overall levels of behavioral problems after school entrance, especially in first and fourth grade. Comorbid ADHD appears to be the explanatory factor of differential problem behavior ratings between children with and without SLDrs

Kindergarteners’ performance in a sound–symbol paradigm predicts early reading

The current study examined the role of serial processing of newly learned sound–symbol associations in early reading acquisition. A computer-based sound–symbol paradigm (SSP) was administered to 243 children during their last year of kindergarten (T1), and their reading performance was assessed 1 year later in first grade (T2). Results showed that performance on the SSP measured before formal reading instruction was associated with later reading development. At T1, early readers performed significantly better than nonreaders in learning correspondences between sounds and symbols as well as in applying those correspondences in a serial manner. At T2, SSP performance measured at T1 was positively associated with reading performance. Importantly, serial application of newly learned correspondences at T1 explained unique variance in first-grade reading performance in nonreaders over and above other verbal predictors, including phonological awareness, verbal short-term memory, and rapid automatized naming. Consequently, the SSP provides a promising way to study aspects of reading in preliterate children

Cognitive development in children of adolescent mothers: The impact of socioeconomic risk and maternal sensitivity

BackgroundAdolescent motherhood is accompanied by a constellation of risk factors that translate into developmental risk for the off-spring. Socioeconomic risk that is associated with adolescent motherhood as well as maternal interactive behaviors may contribute to the impact of adolescent motherhood on children’s developmental outcome.ObjectiveTherefore, the aim of the current study was to investigate differences in children’s cognitive development between children of adolescent and adult mothers in their first two years of life and to examine whether socioeconomic risk (e.g. such as educational and financial problems) and/or maternal sensitivity mediate developmental differences between children of adolescent and adult mothers.MethodsAdolescent mothers (25 years; N = 34) and their infants were included in the current study. Child cognitive development and maternal sensitivity were assessed at three different time points (T1: mean child age 5.26 months; T2: mean child age 14.69 months; T3: mean child age 21.16 months).ResultsChildren of adult mothers showed better cognitive performance at T3 compared to children of adolescent mothers but not at T1 and T2. A multiple mediation model including socioeconomic risk and maternal sensitivity as serial mediators demonstrated that the effect of adolescent motherhood on cognitive development was mediated in a causal effect chain with socioeconomic risk negatively affecting maternal sensitivity and maternal sensitivity affecting children’s cognitive development.DiscussionThe present findings demonstrate that maternal interactive behaviors are not only a simple predictor of cognitive development but may also act as a mediator of the association between more distal variables such as socioeconomic risk and cognitive development in adolescent mothers. This supports the need to promote prevention and intervention programs for adolescent mothers during the early postpartum period to reduce socioeconomic problems and enhance maternal interactive behaviors