Effects of bilateral chemical lesions of the medial basal ganglia [lobus parolfactorius (LPO)] were examined in 7- to 14-d-old domestic chicks. Chicks were trained in a color discrimination task, in which the subject had to peck one of the two colored beads associated with rewards that differed in quantity (amount of food) and/or temporal proximity (delay of food delivery from peck). In experiment 1, food was given without delay, and chicks successfully learned to choose a colored bead that was associated with a larger reward than the other. In experiment 2, a colored bead (red) was associated with a large reward delivered after a delay (D = 1, 2, or 3 sec), whereas another (yellow) was associated with a small reward delivered immediately. In intact and sham-operated conditions, chicks with a longer D chose the red bead progressively fewer times. Selective lesions to the caudal LPO (but not the rostral LPO) caused impulsive choice, and the ablated chicks chose the yellow bead and gained a small-immediate reward regardless of D. However, when retrained in a null-delay condition (D = 0 sec), the lesioned chick chose the red bead again. Ability to associate novel colors with reward was also unimpaired. These results suggest that the LPO may be responsible for the anticipation of reward proximity and involved in a suppression of impulsiveness by which animals seek immediate gains. The present results also indicate a striking similarity in functional roles between the avian LPO and the nucleus accumbens/ventral striatum in mammals.

Social monogamy, typically characterized by the formation of a pair bond, increased territorial defense, and often biparental care, has independently evolved multiple times in animals. Despite the independent evolutionary origins of monogamous mating systems, several homologous brain regions and neuropeptides and their receptors have been shown to play a conserved role in regulating social affiliation and parental care, but little is known about the neuromolecular mechanisms underlying monogamy on a genomic scale. Here, we compare neural transcriptomes of reproductive males in monogamous and nonmonogamous species pairs of Peromyscus mice, Microtus voles, parid songbirds, dendrobatid frogs, and Xenotilapia species of cichlid fishes. We find that, while evolutionary divergence time between species or clades did not explain gene expression similarity, characteristics of the mating system correlated with neural gene expression patterns, and neural gene expression varied concordantly across vertebrates when species transition to monogamy. Our study provides evidence of a universal transcriptomic mechanism underlying the evolution of monogamy in vertebrates.

To understand better the rate of neurogenesis and the distribution of new neurons in posthatch domestic chicks, we describe and compare the expression of the neuronal nuclei protein (NeuN, a.k.a. Fox-3) and doublecortin antigens in the whole brain of chicks 2 days, 8 days, and 14 weeks posthatch. In the forebrain ventricular and paraventricular zones, the density of bromodeoxyuridine-, NeuN-, and doublecortin-labeled cells was compared between chicks 24 hours and 7 days after an injection of bromodeoxyuridine (2 and 8 days posthatch, respectively). The distribution of NeuN-labeled neurons was similar to Nissl-stained tissue, with the exception of some areas where neurons did not express NeuN: cerebellar Purkinje cells and olfactory bulb mitral cells. The ventral tegmental area of 2-day-old chicks was also faintly labeled. The distribution of doublecortin was similar at all timepoints, with doublecortin-labeled profiles located throughout all forebrain areas as well as in the cerebellar granule cell layer. However, doublecortin labeling was not detectable in any midbrain or brainstem areas. Our data indicate that a significant number of new neurons is still formed in the telencephalon of posthatch domestic chicks, whereas subtelencephalic areas (except for the cerebellum) finish their neuronal expansion before hatching. Most newly formed cells in chicks leave the paraventricular zone after hatching, but a pool of neurons stays in the vicinity of the ventricular zone and matures in situ within 7 days. Proliferating cells often migrate laterally along forebrain laminae into still-developing brain areas.

We assembled a de novo transcriptome of short-read Illumina RNA-Seq data generated from telencephalon and diencephalon tissue samples from the Kentish plover, Charadrius alexandrinus. This is a species of considerable interest in behavioural ecology for its highly variable mating system and parental behaviour, but it lacks genomic resources and is evolutionarily distant from the few available avian draft genome sequences. We assembled and identified over 21,000 transcript contigs with significant expression in our samples, showing high homology to exonic sequences in avian draft genomes. From these, we identified >31,000 high-quality SNPs and > 2500 simple sequence repeats (SSRs). We also analysed expression patterns in our data to identify potential candidate genes related to differences in male and female behaviour, identifying over 200 nonoverlapping putative autosomal transcripts that show significant expression differences between males and females. Gene ontology analysis revealed that female-biased transcripts were significantly enriched for cerebral functions related to learning, cognition and memory, and male-biased transcripts were mostly enriched for terms related to neural function such as neuron projection and synapses. This data set provides one of the first de novo transcriptome assemblies from non-normalized short-read next-generation data and outlines an effective strategy for measuring sequence and expression variability simultaneously without the aid of a reference genome.

Stress‐induced cortical alertness is maintained by a heightened excitability of noradrenergic neurons innervating, notably, the prefrontal cortex. However, neither the signaling axis linking hypothalamic activation to delayed and lasting noradrenergic excitability nor the molecular cascade gating noradrenaline synthesis is defined. Here, we show that hypothalamic corticotropin‐releasing hormone‐releasing neurons innervate ependymal cells of the 3rd ventricle to induce ciliary neurotrophic factor (CNTF) release for transport through the brain's aqueductal system. CNTF binding to its cognate receptors on norepinephrinergic neurons in the locus coeruleus then initiates sequential phosphorylation of extracellular signal‐regulated kinase 1 and tyrosine hydroxylase with the Ca2+‐sensor secretagogin ensuring activity dependence in both rodent and human brains. Both CNTF and secretagogin ablation occlude stress‐induced cortical norepinephrine synthesis, ensuing neuronal excitation and behavioral stereotypes. Cumulatively, we identify a multimodal pathway that is rate‐limited by CNTF volume transmission and poised to directly convert hypothalamic activation into long‐lasting cortical excitability following acute stress.