Interferon-gamma (IFN-gamma) coordinates a diverse array of cellular programs through transcriptional regulation of immunologically relevant genes. This article reviews the current understanding of IFN-gamma ligand, receptor, signal transduction, and cellular effects with a focus on macrophage responses and to a lesser extent, responses from other cell types that influence macrophage function during infection. The current model for IFN-gamma signal transduction is discussed, as well as signal regulation and factors conferring signal specificity. Cellular effects of IFN-gamma are described, including up-regulation of pathogen recognition, antigen processing and presentation, the antiviral state, inhibition of cellular proliferation and effects on apoptosis, activation of microbicidal effector functions, immunomodulation, and leukocyte trafficking. In addition, integration of signaling and response with other cytokines and pathogen-associated molecular patterns, such as tumor necrosis factor-alpha, interleukin-4, type I IFNs, and lipopolysaccharide are discussed.

https://jlb.onlinelibrary.wiley.com/doi/epdf/10.1189/jlb.0603252

Interferon-γ: an overview of signals, mechanisms and functions

A DNA test to sex most birds.

Quantifying behavior is crucial for many applications in neuroscience. Videography provides easy methods for the observation and recording of animal behavior in diverse settings, yet extracting particular aspects of a behavior for further analysis can be highly time consuming. In motor control studies, humans or other animals are often marked with reflective markers to assist with computer-based tracking, but markers are intrusive, and the number and location of the markers must be determined a priori. Here we present an efficient method for markerless pose estimation based on transfer learning with deep neural networks that achieves excellent results with minimal training data. We demonstrate the versatility of this framework by tracking various body parts in multiple species across a broad collection of behaviors. Remarkably, even when only a small number of frames are labeled (~200), the algorithm achieves excellent tracking performance on test frames that is comparable to human accuracy.

DeepLabCut: markerless pose estimation of user-defined body parts with deep learning

Over more than a century of research has established the fact that sleep benefits the retention of memory. In this review we aim to comprehensively cover the field of "sleep and memory" research by providing a historical perspective on concepts and a discussion of more recent key findings. Whereas initial theories posed a passive role for sleep enhancing memories by protecting them from interfering stimuli, current theories highlight an active role for sleep in which memories undergo a process of system consolidation during sleep. Whereas older research concentrated on the role of rapid-eye-movement (REM) sleep, recent work has revealed the importance of slow-wave sleep (SWS) for memory consolidation and also enlightened some of the underlying electrophysiological, neurochemical, and genetic mechanisms, as well as developmental aspects in these processes. Specifically, newer findings characterize sleep as a brain state optimizing memory consolidation, in opposition to the waking brain being optimized for encoding of memories. Consolidation originates from reactivation of recently encoded neuronal memory representations, which occur during SWS and transform respective representations for integration into long-term memory. Ensuing REM sleep may stabilize transformed memories. While elaborated with respect to hippocampus-dependent memories, the concept of an active redistribution of memory representations from networks serving as temporary store into long-term stores might hold also for non-hippocampus-dependent memory, and even for nonneuronal, i.e., immunological memories, giving rise to the idea that the offline consolidation of memory during sleep represents a principle of long-term memory formation established in quite different physiological systems.

https://www.zora.uzh.ch/id/eprint/77770/1/physiol_rev_93.pdf

About sleep's role in memory

Human speech and birdsong have numerous parallels. Both humans and songbirds learn their complex vocalizations early in life, exhibiting a strong dependence on hearing the adults they will imitate, as well as themselves as they practice, and a waning of this dependence as they mature. Innate predispositions for perceiving and learning the correct sounds exist in both groups, although more evidence of innate descriptions of species-specific signals exists in songbirds, where numerous species of vocal learners have been compared. Humans also share with songbirds an early phase of learning that is primarily perceptual, which then serves to guide later vocal production. Both humans and songbirds have evolved a complex hierarchy of specialized forebrain areas in which motor and auditory centers interact closely, and which control the lower vocal motor areas also found in nonlearners. In both these vocal learners, however, how auditory feedback of self is processed in these brain areas is surprisingly unclear. Finally, humans and songbirds have similar critical periods for vocal learning, with a much greater ability to learn early in life. In both groups, the capacity for late vocal learning may be decreased by the act of learning itself, as well as by biological factors such as the hormones of puberty. Although some features of birdsong and speech are clearly not analogous, such as the capacity of language for meaning, abstraction, and flexible associations, there are striking similarities in how sensory experience is internalized and used to shape vocal outputs, and how learning is enhanced during a critical period of development. Similar neural mechanisms may therefore be involved.

/pdf/birdsong-and-human-speech-common-themes-and-mechanisms-39gg3m47d4.pdf

BIRDSONG AND HUMAN SPEECH: Common Themes and Mechanisms

The function of bird song is closely linked to sexual selection. A fundamental question regarding the evolution of sexually selected male signals is how their honesty is maintained. The neural space required for storing a large song repertoire size has traditionally been identified as a key constraint. However, it is often forgotten that bird song is a multifaceted behaviour, and that the different characters that comprise it have specific costs. Recent research has revealed the existence of new constraints, such as social aggression or learning opportunities, which limit the expression of several song characteristics. We review the existing evidence for each of these constraints, revealing some major gaps in our knowledge of this fascinating biological system.

The honesty of bird song: multiple constraints for multiple traits

The process through which young male songbirds learn the characteristics of the songs of an adult male of their own species has strong similarities with speech acquisition in human infants. Both involve two phases: a period of auditory memorization followed by a period during which the individual develops its own vocalizations. The avian 'song system', a network of brain nuclei, is the probable neural substrate for the second phase of sensorimotor learning. By contrast, the neural representation of song memory acquired in the first phase is localized outside the song system, in different regions of the avian equivalent of the human auditory association cortex.

Neural mechanisms of birdsong memory

Androgens and estrogens are crucial for the differentiation and function of the vocal control system of songbirds A major source of estrogens in songbirds is the cerebral aromatization of circulating testosterone by aromatase (ARO) In the vocal control system, songbirds have a unique estrogen receptor (ER)-containing area, the nucleus hyperstriatalis ventrale pars caudale (HVC) of the caudal neostriatum Work in the zebra finch has demonstrated ARO expression adjacent to but not in the HVC Compared with other songbirds, such as the canary, the HVC of adult zebra finches contains only few ERs To determine whether the disjunctive distribution of ERs and ARO in the forebrain is a songbird-specific feature, the authors investigated ARO and ER mRNA expression in songbirds (canary, house sparrow, and zebra finch) and in nonsongbirds (budgerigar, ring dove, swift, grey partridge, and barn owl) of five avian orders In addition, the coexpression of androgen receptor (AR) and ARO mRNAs was studied Preoptic hypothalamic areas showed similar expression of ARO in all species In the caudal neostriatum, ARO, AR, and ER transcripts were found only in songbirds ARO and ER mRNA expression in the caudal forebrain was spatially separated, ie, the HVC contained ER mRNA but very little or no ARO mRNA, and the caudomedial neostriatum contained high levels of ARO mRNA but few if any ERs ARO and AR mRNAs, however, were coexpressed in the caudomedial neostriatum The coexpression of ARO mRNA with AR mRNA but not with ER mRNA was found in further brain areas, such as the nucleus posterior lateralis hypothalami The area-specific coexpression of AR, ER, and ARO suggests various possibilities for the steroid-dependent regulation of ARO and for the role of ARO in controlling AR- and ER-dependent mechanisms

Distribution of aromatase, estrogen receptor, and androgen receptor mRNA in the forebrain of songbirds and nonsongbirds.

Estrogens play an important role in the control and differentiation of species-typical behavior and in endocrine homeostasis of birds, but the distribution and evolution of cells that contain estrogen receptors in the avian brain are poorly understood. This study therefore surveys 26 species in the avian orders Anseriformes (1 species), Galliformes (2), Columbiformes (3), Psittaciformes (1), Apodiformes (2), and Passeriformes (3 suboscines, 14 oscines). Indirect immunocytochemistry with the estrogen receptor (ER) antibody H222Spy revealed a general pattern of ER-antibody-immunoreactive cells (ER-IRC) in all 26 species, with ER-IRC in consistent, well-defined locations in the limbic forebrain, the midbrain striatum, the hippocampus, the hindbrain, and especially in the preoptic area and the tuberal hypothalamus. For some species, the microdistribution of ER-IRC in some of these general areas differed, such as in the hippocampus and the anterior hypothalamus of suboscine species and in the preoptic area of the Japanese quail. Brains of oscine songbirds of both sexes, unlike brains of nonsongbirds, had ER-IRC in three specific structures of the nonlimbic forebrain: in the area surrounding the nucleus robustus archistriatalis; in the rostral forebrain; and, for all individuals, in the caudale neostriatum, including the nucleus hyperstriatalis ventrale, pars caudale (HVc). Among songbird families or subfamilies, adult males of the Estrildinae had much lower numbers of ER-IRC in HVc than did adult males of the Fringillidae, Paridae, Sturnidae, and Ploceinae. Differences occurred, too, among closely related species: the songbird canary (Serinus canaria) had an ER-IRC area in the rostral forebrain that was lacking in all other songbird species, including other cardueline finches. The cells with ER that are found only in the songbird forebrain but not in reptiles, nonpasserine birds, and nonoscine passerine birds very likely coevolved with steroid-dependent differentiation of vocal control areas. The songbird-specific expression of ER in the forebrain could be an example in which taxon-specific behavior is due to taxon specific neurochemical properties of the brain. © 1993 Wiley-Liss, Inc.

Manfred Gahr

Papers

The honesty of bird song: multiple constraints for multiple traits

Neural mechanisms of birdsong memory

Distribution of aromatase, estrogen receptor, and androgen receptor mRNA in the forebrain of songbirds and nonsongbirds.

Estrogen receptors in the avian brain: Survey reveals general distribution and forebrain areas unique to songbirds

Distribution and Dynamics in the Expression of Androgen and Estrogen Receptors in Vocal Control Systems of Songbirds