Assessing the size of non-Maori-speakers' active Maori lexicon.

Most non-Maori-speaking New Zealanders are regularly exposed to Maori throughout their lives without seeming to build any extensive Maori lexicon; at best, they know a small number of words which are frequently used and sometimes borrowed into English. Here, we ask how many Maori words non-Maori-speaking New Zealanders know, in two ways: how many can they identify as real Maori words, and how many can they actively define? We show that non-Maori-speaking New Zealanders can readily identify many more Maori words than they can define, and that the number of words they can reliably define is quite small. This result adds crucial support to the idea presented in earlier work that non-Maori-speaking New Zealanders have implicit form-based (proto-lexical) knowledge of many Maori words, but explicit semantic (lexical) knowledge of few. Building on this distinction, we further ask how different levels of word knowledge modulate effects of phonotactic probability on the accessing of that knowledge, across both tasks and participants. We show that participants' implicit word knowledge leads to effects of phonotactic probability-and related effects of neighbourhood density-in a word/non-word discrimination task, but not in a more explicit task that requires the active definition of words. Similarly, we show that the effects of phonotactic probability on word/non-word discrimination are strong among participants who appear to lack explicit word knowledge, as indicated by their weak discrimination performance, but absent among participants who appear to have explicit word knowledge, as indicated by their strong discrimination performance. Together, these results suggest that phonotactic probability plays its strongest roles in the absence of explicit semantic knowledge.

Neuropeptide Y neurons in the nucleus accumbens modulate anxiety-like behavior.

Neuropeptide Y (NPY) is a 36-amino acid neuropeptide that is widely expressed in the central nervous system, including the cerebral cortex, nucleus accumbens (NAc) and hypothalamus. We previously analyzed the behavior of transgenic mice exclusively expressing an unedited RNA isoform of the 5-HT2C receptor. These mice showed decreased NPY gene expression in the NAc and exhibited behavioral despair, suggesting that NAc NPY neurons may be involved in mood disorder; however, their role in this behavior remained unknown. Therefore, in the present study, we investigated the functional role of NAc NPY neurons in anxiety-like behavior by examining the impact of specific ablation or activation of NAc NPY neurons using NPY-Cre mice and Cre-dependent adeno-associated virus. Diphtheria toxin-mediated ablation of NAc NPY neurons significantly increased anxiety-like behavior in the open field and elevated plus maze tests, compared with before toxin treatment. Moreover, chemogenetic activation of NAc NPY neurons reduced anxiety-like behavior in both behavioral tests compared with control mice. These results suggest that NPY neurons in the NAc are involved in the modulation of anxiety in mice.

Different languages, similar encoding efficiency: Comparable information rates across the human communicative niche.

Language is universal, but it has few indisputably universal characteristics, with cross-linguistic variation being the norm. For example, languages differ greatly in the number of syllables they allow, resulting in large variation in the Shannon information per syllable. Nevertheless, all natural languages allow their speakers to efficiently encode and transmit information. We show here, using quantitative methods on a large cross-linguistic corpus of 17 languages, that the coupling between language-level (information per syllable) and speaker-level (speech rate) properties results in languages encoding similar information rates (~39 bits/s) despite wide differences in each property individually: Languages are more similar in information rates than in Shannon information or speech rate. These findings highlight the intimate feedback loops between languages' structural properties and their speakers' neurocognition and biology under communicative pressures. Thus, language is the product of a multiscale communicative niche construction process at the intersection of biology, environment, and culture.

Using a novel PV-Cre rat model to characterize pallidonigral cells and their terminations.

In the present study, we generated a novel parvalbumin (PV)-Cre rat model and conducted detailed morphological and electrophysiological investigations of axons from PV neurons in globus pallidus (GP). The GP is considered as a relay nucleus in the indirect pathway of the basal ganglia (BG). Previous studies have used molecular profiling and projection patterns to demonstrate cellular heterogeneity in the GP; for example, PV-expressing neurons are known to comprise approximately 50% of GP neurons and represent majority of prototypic neurons that project to the subthalamic nucleus and/or output nuclei of BG, entopeduncular nucleus and substantia nigra (SN). The present study aimed to identify the characteristic projection patterns of PV neurons in the GP (PV-GP neurons) and determine whether these neurons target dopaminergic or GABAergic neurons in SN pars compacta (SNc) or reticulata (SNr), respectively. We initially found that (1) 57% of PV neurons co-expressed Lim-homeobox 6, (2) the PV-GP terminals were preferentially distributed in the ventral part of dorsal tier of SNc, (3) PV-GP neurons formed basket-like appositions with the somata of tyrosine hydroxylase, PV, calretinin and cholecystokinin immunoreactive neurons in the SN, and (4) in vitro whole-cell recording during optogenetic photo-stimulation of PV-GP terminals in SNc demonstrated that PV-GP neurons strongly inhibited dopamine neurons via GABAA receptors. These results suggest that dopamine neurons receive direct focal inputs from PV-GP prototypic neurons. The identification of high-contrast inhibitory systems on dopamine neurons might represent a key step toward understanding the BG function.