Blood-feeding in the young adult filarial worms litomosoides sigmodontis

In this study with the filarial model Litomosoides sigmodontis, we demonstrate that the worms ingest host red blood cells at a precise moment of their life-cycle, immediately after the fourth moult. The red blood cells (RBC) were identified microscopically in live worms immobilized in PBS at 4 degrees C, and their density assessed. Two hosts were used: Mongolian gerbils, where microfilaraemia is high, and susceptible BALB/c mice with lower microfilaraemia. Gerbils were studied at 12 time-points, between day 9 post-inoculation (the worms were young 4th stage larvae) and day 330 p.i. (worms were old adults). Only the very young adult filarial worms had red blood cells in their gut. Haematophagy was observed between days 25 and 56 p.i. and peaked between day 28 and day 30 p.i. in female worms. In males, haematophagy was less frequent and intense. Similar kinetics of haematophagy were found in BALB/c mice, but frequency and intensity tended to be lower. Haematophagy seems useful to optimize adult maturation. These observations suggest that haematophagy is an important step in the life-cycle of L. sigmodontis. This hitherto undescribed phenomenon might be characteristic of other filarial species including human parasites

Function and nature of Serial order in Working Memory

Verbal WM defines our ability to temporarily maintain verbal information in an activated and conscious state. This ability not only allows us to maintain the stimuli that have been presented, but importantly, also the order in which the stimuli occur. In the first part of my talk I will demonstrate that this specific aspect of WM, the order processes, are crucial in many cognitive operations such as sentence processing, new vocabulary learning, mental calculation, reading and writing abilities. Using longitudinal, cross-sectional and neuroimaging designs in typical and neurodevelopmental atypical populations, we demonstrated a specific link between serial order WM abilities and different learning abilities. In thesecond part of my talk I will address a fundamental question about the nature of serial order coding in WM. Many current WM models agree on the existence of positional markers for binding items and their serial position in a WM task. However, the models diverge when it comes to defining the nature of serial order coding. These models suggest the possibility of the existence of domain general ordinal positional codes, shared with other domains such as numerical or alphabetical, and based on space and/or time representations. To demonstrate this I will present two recent fMRI studies using MVPA analyses investigating the nature of ordinal representation. The aim of this talk is to give a precise idea of what order WM processing is, what it is used for and how it works

Serial order in working memory: Function and nature of this coding

Verbal WM defines our ability to temporarily maintain verbal information in an activated and conscious state. This ability not only allows us to maintain the stimuli that have been presented, but importantly, also the order in which the stimuli occur. In the first part of my talk I will demonstrate that this specific aspect of WM, the order processes, are crucial in many cognitive operations such as sentence processing, new vocabulary learning, mental calculation, reading and writing abilities. Using longitudinal, cross-sectional and neuroimaging designs in typical and neurodevelopmental atypical populations, we demonstrated a specific link between serial order WM abilities and different learning abilities. In the second part of my talk I will address a fundamental question about the nature of serial order coding in WM. Many current WM models agree on the existence of positional markers for binding items and their serial position in a WM task. However, the models diverge when it comes to defining the nature of serial order coding. These models suggest the possibility of the existence of domain general ordinal positional codes, shared with other domains such as numerical or alphabetical, and based on space and/or time representations. To demonstrate this I will present two recent fMRI studies using MVPA analyses investigating the nature of ordinal representation. The aim of this talk is to give a precise idea of what order WM processing is, what it is used for and how it works

The representation of ordinal information: domain specific or domain general ?

Ordinal processing involves processing of the sequential relations between stimuli of a stimulus set. This crucial ability has been studied extensively and separately in different domains such as working memory (WM) and numerical cognition. Several behavioural and neuroimaging studies suggest the possibility of common ordinal coding mechanisms across different domains. This fMRI study assessed the hypothesis of common ordinal representational mechanisms across the WM, the number and the letter domains. We administered three ordinal judgement tasks (for alphabetical, numerical, and verbal WM judgment) with further manipulation of ordinal distance, and a luminance judgment control task. Our results demonstrated between-task predictions of ordinal distance in fronto-parietal cortices were robust between serial order WM, alphabetical order judgment tasks as well as a luminance judgment control task but not when involving the numerical order judgment tasks. They suggest that common neural substrates characterize processing of ordinal information in WM and alphabetical but not numerical domains. Moreover, additional results suggest that the commonality may reflect attentional control processes involved in judging ordinal distances rather than the intervention of domain-general ordinal codes

The contribution of serial order short-term memory and long-term learning to reading acquisition : a longitudinal study

There is increasing evidence for an association between both serial order short-term memory (STM) and the long-term learning (LTL) of serial order information and reading abilities. In this developmental study, we examined the hypothesis that STM for serial order supports online grapheme-to-phoneme conversion processes during the initial stages of reading acquisition, whereas the LTL of serial order serves reading abilities at later stages, when reading starts to rely on more stable, long-term orthographic representations. We followed a sample of 116 French-speaking children from first (Time 1 [T1]) grade of primary school through second (Time 2 [T2]) and third (Time 3 [T3]) grade. Their serial order STM and LTL abilities as well as their reading abilities were assessed. Overall, we observed that early reading abilities were only predicted by serial order STM performance, while more advanced reading abilities were predicted by both serial order STM and LTL performance. These results point toward a predictive role of serial order memory performance in reading acquisition and suggest that serial order STM and LTL support reading at different stages of acquisition. We further discuss our findings in the light of advancing knowledge about the relationship between memory and reading

The neural representation of ordinal information: domain-specific or domain-general?

Ordinal processing allows for the representation of the sequential relations between stimuli and is a fundamental aspect of different cognitive domains such as verbal working memory (WM), language and numerical cognition. Several studies suggest common ordinal coding mechanisms across these different domains but direct between-domain comparisons of ordinal coding are rare and have led to contradictory evidence. This fMRI study examined the commonality of ordinal representations across the WM, the number and the letter domains by using a multivoxel pattern analysis approach and by focusing on triplet stimuli associated with robust ordinal distance effects. Neural patterns in fronto-parietal cortices distinguished ordinal distance in all domains. Critically, between-task predictions of ordinal distance in fronto-parietal cortices were robust between serial order WM, alphabetical order judgment but not when involving the numerical order judgment tasks. Moreover, frontal ROIs further supported between-task prediction of distance for the luminance judgment control task, the serial order WM and the alphabetical tasks. These results suggest that common neural substrates characterize processing of ordinal information in WM and alphabetical but not numerical domains. This commonality, particularly in frontal cortices, may however reflect attentional control processes involved in judging ordinal distances rather than the intervention of domain-general ordinal codes

The subcutaneous movements of filarial infective larvae are impaired in vaccinated hosts in comparison to primary infected hosts

Our aim in this study was to observe the movements of filarial infective larvae following inoculation into the mammalian host and to assess the effect of vaccination on larval migration, in situ. Here we present recordings of larvae progressing through the subcutaneous tissues and inguinal lymph node of primary infected or vaccinated mice. We used the filaria Litomosoides sigmodontis in BALB/c mice that were necropsied 6 hours after the challenge inoculation of 200 larvae. Subcutaneous tissue sections were taken from the inoculation site and larvae were filmed in order to quantify their movements. Our analyses showed that the subcutaneous larvae were less motile in the vaccinated mice than in primary-infected mice and had more leucocytes attached to the cuticle. We propose that this reduced motility may result in the failure of a majority of larvae to evade the inflammatory reaction, thereby being a possible mechanism involved in the early vaccine-induced protection

Working memory for serial order and numerical cognition: What kind of association?

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