Vocabulary size and speed of word recognition in very young French-English bilinguals: A longitudinal study.

A longitudinal study of lexical development in very young French-English bilinguals is reported. The Computerized Comprehension Test (CCT) was used to directly assess receptive vocabulary and processing efficiency, and parental report (CDI) was used to measure expressive vocabulary in monolingual and bilingual infants at 16 months, and six months later, at 22 months. All infants increased their comprehension and production of words over the six-month period, and bilingual infants acquired approximately as many new words in each of their languages as the monolinguals did. Speed of online word processing was also equivalent in both groups at each wave of data collection, and increased significantly across waves. Importantly, significant relations emerged between language exposure, vocabulary size, and processing speed, with proportion of language exposure predicting vocabulary size at each time point. This study extends previous findings by utilizing a direct measure of receptive vocabulary development and online word processing.

Translation Equivalents Facilitate Lexical Access in Very Young Bilinguals.

The present study investigated the impact of translation equivalents (TE) on lexical processing in a sample of 36 French-English bilingual toddlers at 22-months of age. Children were administered the Computerized Comprehension Task (CCT; Friend & Keplinger, 2003) in each language and parents completed the MacArthur Bates Communicative Development Inventory (CDI) in both English and French across two visits (one language per visit). Correct trials on the CCT were identified and classified into one of two categories: words with a known TE as reported on the CDI and words without a known TE on the CDI. Reaction times for correct trials were then averaged in each category and compared for each of the bilinguals' languages. Interestingly, children were faster to retrieve words with a known TE on the CDI than words with no known TE. The present findings suggest that the translation facilitation effects reported in adult bilinguals are also present in very young bilinguals.

Dog or chien? Translation equivalents in the receptive and expressive vocabularies of young French-English bilinguals.

In order to address gaps in the literature surrounding the acquisition of translation equivalents (TEs) in young bilinguals, two experiments were conducted. In Experiment 1, TEs were measured in the expressive vocabularies of thirty-four French-English bilinguals at 1;4, 1;10, and 2;6 using the MacArthur Bates CDI. Children's acquisition of TEs occurred gradually, with more balanced ratios of exposure and vocabulary associated with larger proportions of TEs at each wave. Experiment 2 compared a direct measure of TE comprehension with parent report of the same set of words. Results showed that parents may over-report children's TE comprehension, as our sample of two-year-old French-English bilinguals (n = 20) comprehended fewer TEs on a direct measure of receptive vocabulary than parents reported on the vocabulary checklist. The present study provides an original contribution to the literature on bilingual vocabulary development by employing both a longitudinal design and a direct measure of TE comprehension.

Vocabulary size, translation equivalents, and efficiency in word recognition in very young bilinguals.

The present study examined early vocabulary development in fifty-nine French monolingual and fifty French-English bilingual infants (1;4-1;6). Vocabulary comprehension was assessed using both parental report (MacArthur-Bates Communicative Development Inventory; CDI) and the Computerized Comprehension Task (CCT). When assessing receptive vocabulary development using parental report, the bilinguals knew more words in their L1 versus their L2. However, young bilinguals were as accurate in L1 as they were in L2 on the CCT, and exhibited no difference in speed of word comprehension across languages. The proportion of translation equivalents in comprehension varied widely within this sample of young bilinguals and was linked to both measures of vocabulary size but not to speed of word retrieval or exposure to L2. Interestingly, the monolinguals outperformed the bilinguals with respect to accuracy but not reaction time in their L1 and L2. These results highlight the importance of using multiple measures to assess early vocabulary development.

Granulocyte macrophage colony-stimulating factor promotes regeneration of retinal ganglion cells in vitro through a mammalian target of rapamycin-dependent mechanism.

Lack of regeneration in the adult central nervous system (CNS) is a major hurdle that limits recovery from neurological ailments. Although accumulating research suggests the possibility of axon regeneration by targeting intrinsic signaling mechanisms, it remains a matter of controversy whether functional recovery can be achieved by manipulating aspects of molecular signaling. Recent studies have shown that granulocyte macrophage colony-stimulating factor (GM-CSF) may be an effective means of targeting repair following CNS injury; how this molecule is able to produce this effect is not known. Indeed, GM-CSF has been shown to promote neuronal survival, potentially through activation of as yet unknown cytokine-dependent signals and potentially through regulation of antiapoptotic mechanisms. It is well established that the loss of intrinsic regenerative ability is highly correlated with development of CNS neurons. We therefore designed experiments, using a well-established in vitro retinal ganglion cell (RGC) culture system, to evaluate the effect of GM-CSF on axon growth and cell survival and define possible mechanisms involved in GM-CSF-mediated effects in vitro. Several developmental stages were evaluated, with particular focus placed on stages at which axon growth is known to be significantly diminished. Our results reveal that GM-CSF not only promotes axon growth in postnatal RGCs but also enhances cell survival through a mammalian target of rapamycin (mTOR)-dependent mechanism.