A quantitative characterization of early neuron generation in the developing zebrafish telencephalon.

The adult brain is made up of anatomically and functionally distinct regions with specific neuronal compositions. At the root of this neuronal diversity are neural stem and progenitor cells (NPCs) that produce many neurons throughout embryonic development. During development, NPCs switch from initial expanding divisions to neurogenic divisions, which marks the onset of neurogenesis. Here, we aimed to understand when NPCs switch division modes to generate the first neurons in the anterior-most part of the zebrafish brain, the telencephalon. To this end, we used the deep learning-based segmentation method Cellpose and clonal analysis of individual NPCs to assess the production of neurons by NPCs in the first 24 h of zebrafish telencephalon development. Our results provide a quantitative atlas detailing the production of telencephalic neurons and NPC division modes between 14 and 24 h postfertilization. We find that within this timeframe, the switch to neurogenesis is gradual, with considerable heterogeneity in individual NPC neurogenic potential and division rates. This quantitative characterization of initial neurogenesis in the zebrafish telencephalon establishes a basis for future studies aimed at illuminating the molecular mechanisms and regulators of early neurogenesis.

Quantification of neuron production and neural progenitor division modes in zebrafish embryonic telencephalon up to 24 h postfertilization using deep learning-based segmentation and clonal analysis methods.

Word Recognition and Word Prediction in Preschoolers With (a Suspicion of) a Developmental Language Disorder: Evidence From Eye Tracking.

Purpose This study compares online word recognition and prediction in preschoolers with (a suspicion of) a developmental language disorder (DLD) and typically developing (TD) controls. Furthermore, it investigates correlations between these measures and the link between online and off-line language scores in the DLD group. Method Using the visual world paradigm, Dutch children ages 3;6 (years;months) with (a suspicion of) DLD (n = 51) and TD peers (n = 31) listened to utterances such as, "Kijk, een hoed!" (Look, a hat!) in a word recognition task, and sentences such as, "Hé, hij leest gewoon een boek" (literal translation: Hey, he reads just a book) in a word prediction task, while watching a target and distractor picture. Results Both groups demonstrated a significant word recognition effect that looked similar directly after target onset. However, the DLD group looked longer at the target than the TD group and shifted slower from the distractor to target pictures. Within the DLD group, word recognition was linked to off-line expressive language scores. For word prediction, the DLD group showed a smaller effect and slower shifts from verb onset compared to the TD group. Interestingly, within the DLD group, prediction behavior varied considerably, and was linked to receptive and expressive language scores. Finally, slower shifts in word recognition were related to smaller prediction effects. Conclusions While the groups' word recognition abilities looked similar, and only differed in processing speed and dwell time, the DLD group showed atypical verb-based prediction behavior. This may be due to limitations in their processing capacity and/or their linguistic knowledge, in particular of verb argument structure.