Pigeon Brain Research Articles

Efferent and afferent connections of the olfactory bulb and prepiriform cortex in the pigeon (Columba livia)

Although olfaction in birds is known to be involved in a variety of behaviors, there is comparatively little detailed information on the olfactory brain. In the pigeon brain, the olfactory bulb (OB) is known to project to the prepiriform cortex (CPP), piriform cortex (CPi), and dorsolateral corticoid area (CDL), which together are called the olfactory pallium, but centrifugal pathways to the OB have not been fully explored. Fiber connections of CPi and CDL have been reported, but those of other olfactory pallial nuclei remain unknown. The present study examines the fiber connections of OB and CPP in pigeons to provide a more detailed picture of their connections using tract-tracing methods. When anterograde and retrograde tracers were injected in OB, projections to a more extensive olfactory pallium were revealed, including the anterior olfactory nucleus, CPP, densocellular part of the hyperpallium, tenia tecta, hippocampal continuation, CPi, and CDL. OB projected commissural fibers to the contralateral OB but did not receive afferents from the contralateral olfactory pallium. When tracers were injected in CPP, reciprocal ipsilateral connections with OB and nuclei of the olfactory pallium were observed, and CPP projected to the caudolateral nidopallium and the limbic system, including the hippocampal formation, septum, lateral hypothalamic nucleus, and lateral mammillary nucleus. These results show that the connections of OB have a wider distribution throughout the olfactory pallium than previously thought and that CPP provides a centrifugal projection to the OB and acts as a relay station to the limbic system.

The effects of avermectin on amino acid neurotransmitters and their receptors in the pigeon brain

The objective of this study was to examine the effects of avermectin (AVM) on amino acid neurotransmitters and their receptors in the pigeon brain. Four groups two-month-old American king pigeons (n=20/group) were fed either a commercial diet or an AVM-supplemented diet (20mg/kg·diet, 40mg/kg·diet, or 60mg/kg·diet) for 30, 60, or 90days. The contents of aspartic acid (ASP), glutamate (GLU), glycine (GLY), and γ-aminobutyric acid (GABA) in the brain tissues were determined using ultraviolet high-performance liquid chromatography (HPLC). The expression levels of the GLU and GABA receptor genes were analyzed using real-time quantitative polymerase chain reaction (qPCR). The results indicate that AVM exposure significantly enhances the contents of GABA, GLY, GLU, and ASP in the cerebrum, cerebellum, and optic lobe. In addition, AVM exposure increases the mRNA expression levels of γ-aminobutyric acid type A receptor (GABAAR), γ-aminobutyric acid type B receptor (GABABR), N-methyl-d-aspartate 1 receptor (NR1), N-methyl-d-aspartate 2A receptor (NR2A), and N-methyl-d-aspartate 2B receptor (NR2B) in a dose- and time-dependent manner. Moreover, we found that the most damaged organ was the cerebrum, followed by the cerebellum, and then the optic lobe. These results show that the AVM-induced neurotoxicity may be associated with its effects on amino acid neurotransmitters and their receptors. The information presented in this study will help supplement the available data for future AVM toxicity studies.

Avermectin induced inflammation damage in king pigeon brain

To determine the effect of Avermectin (AVM) on inflammation damage in king pigeon brain, eighty two-month-old American king pigeons were randomly divided into four groups, and were fed with either commercial diet or AVM-supplemented diet containing 20mgkg−1diet, 40mgkg−1diet, and 60mgkg−1diet AVM for 30, 60 and 90d, respectively. Then, the expression level of inflammatory factors (iNOS, PTGEs, NF-κB), histological damage, and ultra-structural damage were examined. It showed that AVM caused higher expressions (P<0.05) of iNOS, PTGEs, NF-κB with disorganized histological and ultra-structural structures in cerebrum, cerebellum, and optic lobe. Meanwhile, inflammatory and histopathological damage were induced by AVM in king pigeon brains. In addition, the main targeted organelle in nervous system was mitochondria, which indicated that mitochondria may be relevant to the process of inflammation induced by AVM. To our best knowledge, this is the first report to study the toxic effect of AVM on inflammatory damage in king pigeon. Thus, the information presented in this study is believed to be helpful in supplementing data for further AVM toxicity study.

Antioxidant response and histopathological changes in brain tissue of pigeon exposed to avermectin

Avermectins (AVMs) are the active components of some insecticidal and nematicidal products used in agriculture and veterinary medicine for the prevention of parasitic diseases. Residues of AVM drugs or their metabolites in livestock feces have toxic effects on non-target aquatic and terrestrial organisms. In this study, oxidative stress responses and pathological changes on pigeon brain tissues and serum after subchronic exposure to AVM for 30, 60 and 90 days were investigated. The decrease in antioxidant enzyme (superoxide dismutase, SOD and glutathione peroxidase, GSH-Px) activities and increase in methane dicarboxylic aldehyde content in a dose-time-dependent manner in the brain and serum of pigeon were observed. The protein carbonyl content, an indicator of protein oxidation, and DNA-protein crosslink coefficient were significantly augmented with dose-time-dependent properties. The microscopic structures of the cerebrum, cerebellum and optic lobe altered obviously, the severity of which increased with the concentration of AVM and exposure time. The results imply that AVM could induce oxidative damage to the brain tissue and serum of pigeon. The information presented in this study is helpful to understand the mechanism of AVM-induced oxidative stress in birds.

Avermectin exposure induces apoptosis in King pigeon brain neurons

The effect of avermectin was studied on King pigeon brain nerve cells by cytotoxicity [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide, MTT] and apoptosis [acridine orange/ethidium bromide (AO/EB) assay, transmission electron microscope (TEM) evaluation, measurement of mitochondrial membrane potential (Δψm), phosphatidylserine (PS) exposure, caspases activities, DNA fragmentation, reactive oxygen species (ROS) and caspase-3 mRNA expression] within the 2.5–10μgL−1 concentration-range. The results revealed that within the concentrations of 2.5–10μgL−1, avermectin showed obvious cytotoxicity and induced apoptosis in a dose-dependent manner to neurons of King pigeon in vitro. Cell viability were 99.93±8.52%, 82.02±4.99% and 78.23±5.67% after 24h of treatment with avermectin at the concentrations of 0, 2.5 and 5μgL−1, which decreased to 56.36±2.17% of 10μgL−1. Treated cells showed typical apoptosis morphological changes including cytoplasmic vacuolation, chromatin condensation, unclear nuclear membrane and decreased/swollen mitochondria. Typical biochemical hallmarks of apoptosis including Δψm loss, PS exposure, activations of caspase-3, caspase-8 and caspase-9, DNA fragmentation were observed too. Moreover, the levels of ROS in the avermectin treatment groups increased significantly compared to control group. Furthermore, the caspase-3 mRNA levels increased significantly following AVM treatment. In conclusion, our experimental results show that avermectin has cytotoxicity to brain neurons of King pigeon in vitro and the mechanism of neurotoxicity induced by avermectin is closely related to apoptosis.

Large-scale network organization in the avian forebrain: a connectivity matrix and theoretical analysis

Many species of birds, including pigeons, possess demonstrable cognitive capacities, and some are capable of cognitive feats matching those of apes. Since mammalian cortex is laminar while the avian telencephalon is nucleated, it is natural to ask whether the brains of these two cognitively capable taxa, despite their apparent anatomical dissimilarities, might exhibit common principles of organization on some level. Complementing recent investigations of macro-scale brain connectivity in mammals, including humans and macaques, we here present the first large-scale “wiring diagram” for the forebrain of a bird. Using graph theory, we show that the pigeon telencephalon is organized along similar lines to that of a mammal. Both are modular, small-world networks with a connective core of hub nodes that includes prefrontal-like and hippocampal structures. These hub nodes are, topologically speaking, the most central regions of the pigeon's brain, as well as being the most richly connected, implying a crucial role in information flow. Overall, our analysis suggests that indeed, despite the absence of cortical layers and close to 300 million years of separate evolution, the connectivity of the avian brain conforms to the same organizational principles as the mammalian brain.

Identification of two forebrain structures that mediate execution of memorized sequences in the pigeon

The execution of action sequences is the basis of most behavior. However, little is known about the neural foundation of visuomotor sequence execution in birds, although pigeons are a classic model animal to study sequence learning and production. Recently, we identified two structures in the pigeon brain, the nidopallium intermedium medialis pars laterale (NIML) and the nidopallium caudolaterale (NCL), that are involved in the execution of a serial reaction time task (SRTT). In the SRTT sequence execution is always cue guided. Thus the previous study could not unambiguously clarify whether NCL and NIML contribute to a memory-based execution of sequential behavior. In addition, a possibly differential role of these two structures could not be identified. Therefore, the present study was conducted to further elucidate the role of NCL and NIML in sequence execution in a task where pigeons performed a memorized four-item sequence. Transient inactivation of each NIML and NCL severely impaired sequence execution. The results confirm and extend our previous findings. NIML and NCL seem to store sequence information in parallel. However, the results support the hypothesis that NCL, in contrast to NIML, is especially required for sequence initiation.

Distribution and characterization of doublecortin-expressing cells and fibers in the brain of the adult pigeon (Columba livia)

Doublecortin (DCX) is a microtubule-associated protein essential for the migration of immature neurons in the developing and adult vertebrate brain. Herein, the distribution of DCX-immunoreactive (DCX-ir) cells in the prosencephalon of the adult pigeon (Columba livia) is described, in order to collect the evidence of their immature neural phenotype and to investigate their putative place of origin. Bipolar and multipolar DCX-ir cells were observed to be widespread throughout the parenchyma of the adult pigeon forebrain. Small, bipolar and fusiform DCX-ir cells were especially concentrated at the tips of the lateral walls of the lateral ventricles (VZ) and sparsely distributed in the remaining ependyma. Multipolar DCX-ir cells populated the pallial regions. None of these DCX-ir cells seemed to co-express NeuN or GFAP, suggesting that they were immature neurons. Two different migratory-like routes of DCX-ir cells from the VZ toward different targets in the parenchyma were putatively identified: (i) rostral migratory-like bundle; and (ii) lateral migratory-like bundle. In addition, pial surface bundles and intra-ependymal fascicles were also observed. Pigeons treated with 5-bromo-desoxyuridine (BrdU, 3 intraperitoneal injections of 100mg/kg 2h apart, sacrificed 2h after last injection) displayed BrdU-immunoreactive cells (BrdU-ir) in VZ and ependyma whereas the parenchyma was free of such cells. Despite the regional overlapping, there was no evidence of double-labeling between BrdU and DCX. Therefore, the VZ in the brain of adult pigeons seems to have rapidly dividing cells as putative progenitors of newborn neurons populating the forebrain. The distribution of the newborn neurons in the avian prosencephalon and their migration pathways appear to be larger than in mammals, suggesting that the morphological turnover of forebrain circuits is an important mechanism for brain plasticity in avian species during adulthood.

An Avian Magnetometer

Neurons in the pigeon brain encode information on Earth's magnetic field for orientation and navigation.

Neural Correlates of a Magnetic Sense

Many animals rely on Earth's magnetic field for spatial orientation and navigation. However, how the brain receives and interprets magnetic field information is unknown. Support for the existence of magnetic receptors in the vertebrate retina, beak, nose, and inner ear has been proposed, and immediate gene expression markers have identified several brain regions activated by magnetic stimulation, but the central neural mechanisms underlying magnetoreception remain unknown. Here we describe neuronal responses in the pigeon's brainstem that show how single cells encode magnetic field direction, intensity, and polarity; qualities that are necessary to derive an internal model representing directional heading and geosurface location. Our findings demonstrate that there is a neural substrate for a vertebrate magnetic sense.

A 3-dimensional digital atlas of the ascending sensory and the descending motor systems in the pigeon brain

Pigeons are classic animal models for learning, memory, and cognition. The majority of the current understanding about avian neurobiology outside of the domain of the song system has been established using pigeons. Since MRI represents an increasingly relevant tool for comparative neuroscience, a 3-dimensional MRI-based atlas of the pigeon brain becomes essential. Using multiple imaging protocols, we delineated diverse ascending sensory and descending motor systems as well as the hippocampal formation. This pigeon brain atlas can easily be used to determine the stereotactic location of identified neural structures at any angle of the head. In addition, the atlas is useful to find the optimal angle of sectioning for slice experiments, stereotactic injections and electrophysiological recordings. This pigeon brain atlas is freely available for the scientific community.

Serotonin 5-HT1A receptor binding sites in the brain of the pigeon (Columba livia)

Present knowledge about the serotonergic system in birdbrains is very limited, although the pigeon was used as an animal model in various studies focused on the behavioral effects of serotonergic transmission. In the mammalian brain the 5-HT(1A) receptor is the most widespread serotonin receptor type, and is involved in various functions. Less is known about the distribution of 5-HT(1A) receptors in the avian species. Therefore, we analyzed serotonin 5-HT(1A) receptor binding sites in the pigeon brain using quantitative in vitro receptor autoradiography with the selective radioligand [³H]-8-hydroxy-2-(di-n-propylamino)tetralin ([³H]-8-OH-DPAT). The receptor is differentially distributed throughout the pigeon brain. High levels of 5-HT(1A) receptors are found in the nucleus pretectalis (PT). Moderate densities were detected in the tectum, as well as in the telencephalic nidopallium and hyperpallium. Very low levels were found in the hippocampal formation, the amygdaloid complex, the basal ganglia, and several thalamic nuclei. Furthermore, local variations in 5-HT(1A) receptor densities support the concept of further subdivisions of the entopallium. The regional distribution patterns of 5-HT(1A) receptors mostly display a similar distribution as found in homologue brain structures of mammals.

Homing pigeons as a model for the influence of experience on brain composition-including considerations on evolutionary theory

The brain of homing pigeons seems to be functionally adapted to homing with e.g. larger hippocampi and olfactory bulbs. Furthermore, functional lateralization occurs as well in homing pigeons. Recently, the investigation of the influence of navigational experience on brain composition and lateralization revealed larger hippocampi in homing pigeons with navigational experience compared to unexperienced homing pigeons. Additionally, there are several brain structures in homing pigeons which show a volumetrical lateralization, whereat homing pigeons with navigational experience show a more lateralized brain than pigeons without navigational experience. This gives more insights in the neuronal basis of orientation and brain development in general but demonstrates as well its complexity. Plasticity and lateralization are much more correlated with individual life history than assumed up to date and have to be more considered in comparative research of evolution.

Asymmetry of different brain structures in homing pigeons with and without navigational experience

Homing pigeons (Columba livia f.d.) are well-known for their homing abilities, and their brains seem to be functionally adapted to homing as exemplified, e.g. by their larger hippocampi and olfactory bulbs. Their hippocampus size is influenced by navigational experience, and, as in other birds, functional specialisation of the left and right hemispheres ('lateralisation') occurs in homing pigeons. To show in what way lateralisation is reflected in brain structure volume, and whether some lateralisation or asymmetry in homing pigeons is caused by experience, we compared brains of homing pigeons with and without navigational experience referring to this. Fourteen homing pigeons were raised under identical constraints. After fledging, seven of them were allowed to fly around the loft and participated successfully in races. The other seven stayed permanently in the loft and thus did not share the navigational experiences of the first group. After reaching sexual maturity, all individuals were killed and morphometric analyses were carried out to measure the volumes of five basic brain parts and eight telencephalic brain parts. Measurements of telencephalic brain parts and optic tectum were done separately for the left and right hemispheres. The comparison of left/right quotients of both groups reveal that pigeons with navigational experience show a smaller left mesopallium in comparison with the right mesopallium and pigeons without navigational experience a larger left mesopallium in comparison with the right one. Additionally, there are significant differences between left and right brain subdivisions within the two pigeon groups, namely a larger left hyperpallium apicale in both pigeon groups and a larger right nidopallium, left hippocampus and right optic tectum in pigeons with navigational experience. Pigeons without navigational experience did not show more significant differences between their left and right brain subdivisions. The results of our study confirm that the brain of homing pigeons is an example for mosaic evolution and indicates that lateralisation is correlated with individual life history (experience) and not exclusively based on heritable traits.

Afferent and efferent projections of the central caudal nidopallium in the pigeon (Columba livia)

The central caudal nidopallium (NCC) is a large subdivision of the nidopallium in the pigeon brain, but its connectional anatomy is unknown. Here, we examined the connections of NCC by using tract-tracing methods. Injections of cholera toxin B-chain (CTB) in NCC labeled many neurons within NCC. Outside NCC, many labeled neurons were found in the dorsal intermediate mesopallium and medialmost part of the medial intermediate nidopallium, with a few in the intermediate (AI) and medial (AM) arcopallium. In the thalamus, labeled neurons were located in the subrotundal nucleus, the shell region of nucleus ovoidalis, and the caudal part of the dorsolateral posterior thalamic nucleus. Injections of biotinylated dextran amine (BDA) in NCC labeled many fibers running rostrocaudally within NCC. Some of these terminated in the dorsal intermediate mesopallium, but the size of the terminal field was smaller than the region of the dorsal intermediate mesopallium that provided the projection to NCC. NCC sent numerous efferents to AI and AM but few to the thalamus. In contrast, after CTB injections in the dorsal intermediate mesopallium, a few neurons were labeled in NCC, but, after BDA injections in the dorsal intermediate mesopallium, large numbers of labeled fibers were seen to project widely throughout NCC. These findings indicate that the flow of information is predominantly from the dorsal intermediate mesopallium to NCC and from there to the arcopallium (AI and AM). The arcopallial outflow to the medial hypothalamus could imply that NCC is involved in neuroendocrine and autonomic functions and is limbic in nature.

Pigeon ‘black box’ offers clues to navigation

A gadget that monitors the brain and GPS-location of pigeons in flight suggests that brain activity spikes at prominent landmarks

Comparative quantitative investigations on brains of rock doves, domestic and urban pigeons (Columba 1. livia)1

Summary The volumes of brain and brain structures in rock doves, domestic and urban pigeons were determined from frontal serial sections. By means of allometric methods a total reduction of the brain by 6.86% were examined for domestic and urban pigeons. This reduction is composed of differently dimensioned changes of brain subdivisions: medulla oblongata 1.94%, cerebellum 3.76%, mesencephalon 9.43%, diencephalon 10.38% and telencephalon 7.05%. The highest decrease was found in the hyperstriatum ventrale (12.21%) and optic tectum (12.05%), the lowest in the olfactoric structures (0.59%). Increase in volume was observed in the palaeostriatal complex (2.78%). Changes in brain size in domestic birds were compared with observations in domestic mammals, and were discussed as due to the environmental changes in domestication and according to cephalization. Zusammenfassung Vergleichend quantitative Untersuchungen an Gehirnen von Felsen-, Haus- und Stadttauben (Columba I. livia) Mit Hilfe cytoarchitektonischer Methoden wurden die Volumina einzelner Hirnteile von Haus- und Stadttauben im Vergleich zur Stammart bestimmt, um die bei vergleichend-allometrischen Untersuchungen an Organen festgestellte Himgrößenabnahme von 6,86% zu analysieren. Die Reduktion des Gehirns bei Haus- und Stadttauben betraf nicht alle Himgebiete in gleicher Weise and ergab für: Medulla oblongata 1,94%, Cerebellum 3,76%, Mesencephalon 9,43%, Diencephalon 10,38% und Telencephalon 7,05%. Die größte Abnahme zeigten das Hyperstriatum ventrale (12,21%) sowie das Tectum opticum (12,05%), während die olfaktorischen Strukturen mit 0,59% nahezu unverändert waren. Eine Volumenzunahme wurde für den palaeostriatalen Komplex festgestellt (2,78%). Die Untersuchungen orientierten sich an entsprechenden Arbeiten fiber Haussäuger. Dabei warden Parallelen und Abweichungen in der Hirngrößenänderung bei domestizierten Sáugern and Vögeln im Vergleich zu ihren Stammarten beobachtet. Auch für Hausvögel scheint zuzutreffen, daß das Cerebralisationsniveau das Ausmaß der Hirnreduktion bestimmt.

The Journal of Biological Chemistry, Volume 203, 1953: Enzyme secretion and the incorporation of P32 into phospholipides of pancreas slices.

1. When enzyme secretion was stimulated by carbamylcholine or acetylcholine (with eserine) in slices of pigeon pancreas, the incorporation of P32 into the phospholipide fraction of the stimulated slices was, after 2 hours, 4.8 to 8.7 (average, 7.0) times greater than the incorporation of P32 into the phospholipides of control slices. Neither respiration nor the incorporation of P32 into acid-soluble phosphate esters was increased. 2. Pilocarpine, which on a weight for weight basis was much less effective than carbamylcholine or acetylcholine in stimulating enzyme secretion in pancreas slices, was also much less effective in stimulating the uptake of P32 into phospholipides. 3. The stimulatory effects of carbamylcholine on both enzyme secretion and the incorporation of P32 into phospholipides were abolished by atropine. 4. The specific activity of the phospholipides from slices incubated anaerobically was less than 5 per cent of that observed aerobically. Anaerobically, carbamylcholine did not stimulate the incorporation of P32 into phospholipides to any significant extent. The specific activity of the acid-soluble phosphate esters after anaerobic incubation was 34 per cent of that found aerobically. 5. Cholinergic drugs had little or no effect on the incorporation of P32 into the phospholipides of the following tissue slices: pigeon and guinea pig liver, guinea pig heart ventricle, pigeon gizzard (smooth muscle), and guinea pig kidney cortex. A relatively slight stimulation of P32 uptake into phospholipides was observed in slices of pigeon brain (65 per cent) and guinea pig brain cortex (40 per cent). 6. Stimulation of amylase synthesis in slices of pigeon pancreas by the addition of a mixture of amino acids had no effect on the incorporation of P32 into phospholipides.

Dual coding of visual asymmetries in the pigeon brain: the interaction of bottom-up and top-down systems

The pigeon's visual system is an excellent model to investigate the ontogenetic and the neuronal foundations of cerebral asymmetries. Before hatching, lateralized visual stimulation induces structural asymmetries within the tectofugal pathway during a critical time window. Interhemispheric control mechanisms emerge presumably after hatching and stabilize these induced asymmetries. Once established, visual asymmetry in pigeons displays a left hemispheric dominance for complex learning and discrimination tasks and unravels how the interplay between bottom-up and top-down mechanisms generate a lateralized, hemispheric-specific visual analysis. The ascending visual (tectofugal) pathway displays cell size asymmetries and directs more bilateral visual information towards the left hemisphere. This bottom- up system is controlled by telencephalic top-down projections, which affect intra- and/or interhemispheric inhibitory systems in a presumably lateralized manner. Such a flexible organization allows the control of information transfer depending on the visual input and hence adapt the dominant processing mode to environmental requirements.

Immunohistochemical distribution of AMPA-type label in the pigeon ( C. livia) hippocampus

The avian hippocampal formation (HF) is reported to have a role equivalent to that of the mammalian hippocampus, which may involve the glutamatergic system as well. In the present paper we offer evidence of the occurrence and distribution of the subunits composing AMPA-type glutamate receptors on neurons in the hippocampus region of the pigeon brain. The experiment analyzed the immunolabeling of glutamate receptor (GluR) 1 , GluR 4, and GluR 2/3 receptor subunits in adult pigeons and found consistent evidence that neurons located in the five main areas of the avian HF have these AMPA-type subunits, but their incidence varies according to position and neuro-type. About 20%–35% of the irregular and 35%–70% of the triangular neurons on the lateral and medial “V” arms contain GluR 1 and GluR 2/3, while GluR 4 was found only at rounded neurons. The majority of the triangular neurons (over 90%) and about half of the irregular neurons in the medial area contain GluR 1 and GluR 2/3, whereas the rounded neurons contain primarily GluR 4 (95%). Labeling revealed GluR 1 (40%–60%) and GluR 2/3 (30%) in the dorsomedial and lateral areas but only in irregular neurons, while 60%–80% of the rounded neurons synthesize GluR 4. While triangular and irregular neurons appear to match the description of projecting neurons, rounded ones seem to participate in local circuits. A discussion of the functional significance of the avian HF concentrates on a postulation of the “V” arms as equivalent to the dentate gyrus and the dorsomedial area being similar to the Ammon's horn.