Musculotopic innervation of the primary flight muscles, the pectoralis (Pars thoracicus) and supracoracoideus, of the pigeon (Columba livia): a WGA-HRP Study

The distribution of motoneurons innervating the primary depressor and elevator muscles of the wing of the domestic pigeon (Columba livia) was studied by using the retrograde axonal tracer lectin-conjugated horseradish peroxidase (WGA-HRP). Injection of WGA-HRP into the pectoralis (pars thoracicus) labeled neurons in the ventromedial corner of the lateral motor column of the spinal cord. These neurons were arranged in a column extending from spinal segment X or XI to spinal segment XII or XIII. The pectoralis, the primary depressor muscle of the wing, consists of two parts which are anatomically and functionally distinct, the sternobrachialis (SB) and thoracobrachialis (TB). Injection into the SB labeled neurons in the rostral and middle regions of the pectoralis motoneuron column. In contrast, injection into the TB labeled neurons in the middle and caudal regions of the pectoralis motoneuron column. Injection into the primary elevator muscle of the wing, the supracoracoideus, labeled neurons in the lateral motor column in spinal segments X and XI. These motoneurons were located dorsolateral to motoneurons labeled following pectoralis injection. These data demonstrate musculotopic segregation of the motoneurons innervating the primary flight muscles in the pigeon and, further, illustrate that the SB and TB subregions of the pectoralis are innervated by discrete aggregations of motoneurons.     

Stabilizing gaze reflexes in the pigeon (Columba livia)

The vestibulo-ocular reflex (VOR) and the closed-loop vestibulo-collic reflex (CL-VCR) were investigated in the pigeon. The animals, placed either in the fixed-head condition (VOR) or in the free-head condition (CL-VCR) were rotated in darkness (vestibular responses) or in the presence of visual surroundings (visuo-vestibular responses). The linear range of the reflexes were determined both in the frequency and in the velocity domains. Results show that: 1. Pigeons develop a strong VOR, which presents the same asymmetry observed with the OKN, the gain being higher when the slow-phase occurs in the T-N direction. This asymmetry persists in the light (VOR + OKN). In the free-head condition, both the eye and the head display a synchronized nystagmus whose effects are additive. The head reflex (CL-VCR) contributes about 80% of the gaze stabilization. 2. In the medium-low frequency range, the head response (CL-VCR) has a lower gain than the VOR (head-fixed), but the gain of both reflexes increases with frequency, up to about 1 at 0.6-1 Hz. The gaze response (eye + head) presents an optimal gain above 0.06 Hz. The phase lead is higher for the VOR than for the CL-VCR (40 degrees and 32 degrees respectively at 0.03 Hz), but both phases also become nul around 1 Hz. The time constants are 6.5 s for the VOR, 8.5 s for the CL-VCR and 9.6 s for the gaze response (VOR + CL-VCR). 3. While the VOR gain shows a saturation at peak stimulation velocities (PV) higher than 20 degrees/s (at 0.3 Hz), the CL-VCR gain is linear at least up to 60 degrees/s (the highest PV used). However, the phase lead declines when the PV is greater than 20 degrees/s, both for the VOR and the CL-VCR. 4. When the vestibular stimulation is delivered in the light (visuo-vestibular stimulation), there is no phase shift. The VOR gain (fixed-head) is optimal and linear over the entire frequency range, but it saturates for PV higher than 40 degrees/s. In the free-head condition, while the gaze gain is linear and close to 1 in both the frequency and the velocity domains, the head response gain (CL-VCR) remains lower especially in the low frequency and in the low velocity ranges.     

Rhabdomyosarcoma in a racing pigeon (Columba livia)

An adult racing pigeon (Columba livia) was presented with a subcutaneous mass on the ventral aspect of the right wing. A fine-needle aspirate and radiographic study of the mass were suggestive of highly invasive sarcomatous neoplasm. Euthanasia was decided because of the poor prognosis. Necropsy confirmed the highly invasive nature of the neoplasm, which also occupied a large portion of the right breast. There also was extensive osteolysis of the sternum with neoplastic invasion of the left breast and the coelomic cavity. Histopathology revealed a highly cellular, poorly demarcated, unencapsulated invasive sarcoma. Immunohistochemistry was positive for muscle actin, and myoglobin, weakly positive for vimentin, and negative for desmin, neuron-specific enolase and S-100 protein, suggesting a diagnosis of undifferentiated rhabdomyosarcoma.     

Stabilizing gaze reflexes in the pigeon (Columba livia)

Summary A quantitative study of horizontal and vertical optokinetic nystagmus (OKN) and optocollic reflex (OCR) has been performed in the pigeon using the search-coil technique. The reflexes were analysed in response to either velocity steps or sinusoidal stimulation. Results show that: 1. In response to a velocity step stimulation, the slow phase velocity of both OKN and OCR increases gradually to reach a steady state level. When the stimulation stops in the dark, After Responses (OKAN-I, OKAR-I) occur. Time constants of the OKN charge (or OCR charge) and of the After Responses are lower for vertical than for horizontal responses. 2. In the free-head condition, both the head and the eye display a synchronized nystagmus which add their effects. However, the head reflex (OCR) accounts for about 80–90% of the entire linear gaze response (head + eye), except for the vertical steady state responses which are wholly accomplished by the head (OCR). 3. Both closed-loop and open-loop gains of steady state responses are higher for horizontal than for vertical reflexes. Vertical OCR, horizontal OKN and vertical OKN show properties of binocular integration, the response gain being higher for binocular than for monocular stimulations. By contrast, the horizontal OCR shows little binocular integration but displays a higher response gain for monocular stimulation, compared to horizontal OKN. 4. The horizontal OKN elicited by both monocular and binocular stimulation is asymmetrical, the gain being higher when the eye is driven by a temporo-nasal stimulation. In contrast, both vertical OKN and vertical OCR are practically symmetrical. 5. While both the gain of horizontal OKN and its linear range (up to 20°/s) are improved when the head is free (gaze gain close to 1 up to 40°/s), the vertical OKN and the vertical OCR have similar gain profiles and similar domains of linearity (up to 10°/s). 6. In response to increasing the frequency of a sinusoidal stimulation at constant peak velocity, all the reflexes display a drop in gain and a strong increase of phase lag. The phase increase is greater for horizontal than for vertical reflexes. On the other hand, both gain and phase are higher for OCR than for OKN, both in the horizontal plane as well as in the vertical plane. 7. For sinusoidal stimulations, when the peak velocity (PV) is increased at a constant frequency (0.03 Hz), nonlinearities appear (drop in gain, phase increase) both for OKN and OCR. While the most important parameter which determines the phase is the stimulation frequency, both peak velocity and peak acceleration are involved in the gain saturation.     

Food preferences in the pigeon (Columba livia).

Pigeons offered a choice among several different types of seed presented separately in substantial quantities, show individual patterns of seed selection behavior which persist over prolonged periods. The relations among several different measures of selection were examined under a variety of presentation conditions and following experimental manipulations (food deprivation or trigeminal deafferentation) designed, respectively, to increase and decrease hunger. Different measures of selection were differentially affected by the manipulations, suggesting that they reflect the operation of different causal mechanisms. The results indicate that the pigeon's selection behavior is controlled by many of the same processes that normally control its quantitative intake.     

Multisensory convergence in the thalamus of the pigeon (Columba livia)

Neuronal activity was extracellularly recorded from the nucleus dorsolateralis posterior thalami (DLP) of anesthetized pigeons. The sensitivity of individual cells to stimuli of different sensory modalities: somatosensory, visual and auditory was investigated. A substantial population of the DLP neurons responded to mechanical stimulation of large, often bilateral areas of the animal's body surface. No somatotopic organization could be detected. The functional properties of these neurons resembled those described for mammalian nucleus posterior thalami neurons. The visually responsive cells could be driven from large areas of the visual field. Auditory sensitive neurons were optimally activated by wideband noise. Twenty-nine percent of the DLP recorded neurons showed polysensory properties responding either to somatosensory and visual or to somatosensory and auditory stimuli.     

Immunological responsiveness of the pigeon (Columba livia) following neonatal bursectomy

Pigeon squabs in two separate experiments were surgically bursectomized ( BSX ), surgically sham bursectomized ( SBSX ), or maintained as non-surgical controls (CON). Surgical procedures were performed within 2 hr of hatching. Primary and secondary hemagglutinin (HA) responses, as well as mercaptoethanol sensitive (ME-S) and resistant (ME-R) levels, to sheep red blood cells (SRBC) were quantitated. BSX did not reduce HA responses, nor ME-S and ME-R levels.     

Gas exchange during high-frequency ventilation in the pigeon (Columba livia)

We studied the effect of high-frequency ventilation (HFV) on the gas exchange of tracheotomized pigeons. The pigeons were artificially ventilated using a piston pump, which alternately connected the pigeons' airways to a constant-flow source. Two-minute periods of HFV were interposed between long periods of normal ventilation. The effect of HFV was assessed by the recorded changes in the PO2, PCO2 and pH of arterial blood and from the changes in the composition of the gas in the interclavicular air sacs. The results showed that HFV can augment gas exchange when the tidal volume (VT) is less than the volume of the anatomical dead space (VD). However, normal arterial gas composition can only be maintained if respiratory frequency is high (greater than 20 Hz). At the normal panting frequency of pigeons (7.8 Hz), gas exchange can thus only be maintained if tidal volume is approximately 125% of the dead space. When panting the VT must be greater than the VD. This finding agrees with the results of recent work showing flush-out- or compound-panting in birds: i.e. if, during panting, VT approaches close to the VD, intermittent interruptions, by taking deeper breaths in order to ensure a supply of fresh air to the lungs, are necessary.     

Failure of nitro-imidazole drugs to control trichomoniasis in the racing pigeon (Columba livia domestica)

The nitro-imidazole drugs ronidazol. dimetridazol, metronidazol and carnidazol failed to control Trichomonas gallinae in the racing pigeon, presumably due to acquired drug resistance.     

Distribution of serotonin-immunoreactivity in the brain of the pigeon (Columba livia)

The distribution of serotonin (5-HT)-containing perikarya, fibers and terminals in the brain of the pigeon (Columba livia) was investigated, using immunohistochemical and immunofluorescence methods combined with retrograde axonal transport. Twenty-one different groups of 5-HT immunoreactive (IR) cells were identified, 2 of which were localized at the hypothalamic level (periventricular organ, infundibular recess) and 19 at the tegmental-mesencephalic and rhombencephalic levels. Ten of the cell groups were situated within the region of the midline from the isthmic to the posterior rhombencephalic level and constituted the raphe system (nucleus annularis, decussatio brachium conjunctivum, area ventralis, external border of the nucleus interpeduncularis, zona peri-nervus oculomotorius, zona perifasciculus longitudinalis medialis, zona inter-flm, nucleus linearis caudalis, nucleus raphe superior pars ventralis, nucleus raphe inferior). The 9 other cell populations belonged to the lateral group and extended from the posterior mesencephalic tegmentum to the caudal rhombencephalon [formatio reticularis mesencephali, nucleus ventrolateralis tegmenti, ectopic area (Ec) of the nucleus isthmo-opticus (NIO), nucleus subceruleus, nucleus ceruleus, nucleus reticularis pontis caudalis, nucleus vestibularis medialis, nucleus reticularis parvocellularis and nucleus reticularis magnocellularis]. Combining the retrograde axonal transport of rhodamine β-isothiocyanate (RITC) after intraocular injection and immunohistofluorescence (fluoresceine isothiocyanate: FITC/5-HT) showed the centrifugal neurons (NIO, ec) to be immunonegative. Serotonin-IR fibers and terminals were found to be very broadly distributed within the brain and were particularly prominent in several structures of the telencephalon (archistriatum pars dorsalis, nucleus taeniae, area parahippocampalis, septum), diencephalon (nuclei preopticus medianus, magnocellularis, nucleus geniculatus lateralis pars ventralis, nucleus triangularis, nucleus pretectalis), mesencephalon-rhombencephalon (superficial layers of the optic tectum, nucleus ectomamillaris, nucleus isthmo-opticus and in most of the cranial nerve nuclei). Comparing the present results with those of previous studies in birds suggests some major serotonin containing pathways in the avian brain and clarifies the possible origin of the serotonin innervation of some parts of the brain. Moreover, comparing our results in birds with those obtained in other vertebrate species shows that the organization of the serotoninergic system in many regions of the avian brain is much like that found in reptiles and mammals.     

Morphological study of the vas deferens of the pigeon (Columba livia)

A morphological study of the vas deferens of the pigeon was carried out in order to determine the electronmicroscopic features of its epithelial lining, and the expression of pancytokeratins. The results showed that the epithelium is columnar pseudostratified and consists of non-ciliated (principal) cells and basal cells. Presence of a predominantly granular endoplasmic reticulum, mitochondria and well-developed Golgi complexes bearing vesicles on their cis/trans surfaces were observed. In addition to these vesicles associated with the Golgi complexes were observed membrane-delimited vesicles with a low electron density content or with an electrondense content mainly related to the endoplasmic reticulum. Apical cytoplasmic expansions with heterogeneous cytoplasmic content were also seen. These subcellular features associated to the presence of pancytokeratins, suggest the occurrence of a secretory process in principal cells, as well provide a mural structural support to the vas deferens.     

Electrophysiological investigation of the archistriato-hypothalamic pathway in the pigeon (Columba livia)

The connection from the limbic part of the avian archistriatum (Am+Ap) to the hypothalamus by way of the tractus occipito-mesencephalicus, pars hypothalami (HOM) was investigated electrophysiologically by means of electrical stimulation in the archistriatum and extracellular single unit recording in the hypothalamus. A powerful activating influence of Am on the hypothalamus could be demonstrated, which involved not only the established termination region of HOM in the posterior hypothalamus, but also the lateral and anterior hypothalamus, the stratum cellulare internum (SCI) and externum (SCE). The response patterns in the medial region differ in a characteristic manner from those in the lateral and posterior regions. Whereas neurons in the medial hypothalamus have small amplitudes (0.2 mV) and are evoked with relatively long latencies (>8 ms), responses in the remaining regions appear to have higher amplitudes (up to 1 mV) and faster conduction velocities.The results are not in conflict with the presence of the postulated [25] direct anatomical pathway, but monosynaptic transmission was proven neither for the projection to the medial nor for that to the lateral region. The spontaneous activity of some neurons in LHy, SCI and SCE was inhibited by Am stimulation. It is concluded that the HOM-tract includes several pathways mediating slow and fast, monosynaptic and polysynaptic excitatory and inhibitory effects. These observations on the archistriato-hypothalamic connections in the pigeon compare with those on amygdalo-hypothalamic projections via stria terminalis in the rat and contrast with the more complex organization of these pathways encountered in higher mammals.Abbreviations Aa Archistriatum anterior - AHM Nucleus anterior medialis hypothalami - Ai Archistriatum intermedium - Aid Archistriatum intermedium, pars dorsalis - AL Ansa lenticularis - Am Archistriatum mediale - Ap Archistriatum posterior - CO Chiasma opticum - CoS Nucleus commissuralis septi - DA Tractus archistriatalis dorsalis - DIP Nucleus dorsointermedius posterior thalami - DLL Nucleus dorsolateralis anterior thalami. pars lateralis - DLM Nucleus dorsolateralis anterior thalami. pars medialis - DLP Nucleus dorsolateralis posterior thalami - DMA Nucleus dorsomedialis anterior thalami - DMP Nucleus dorsomedialis posterior - TA Tractus-frontoarchistriatalis - FPL Fasciculus prosencephali lateralis - GLv Nucleus geniculatus lateralis, pars ventralis - HOM Tractus occipitomesencephalicus, pars hypothalami - IPS Nucleus interstitio-pretecto-subpretectalis - LA Nucleus lateralis anterior thalami - LHy Hypothalamus lateralis - nST Nucleus striae terminalis - OM Tractus occipitomesencephalicus - Ov Nucleus ovoidalis - PA Paleostriatum augmentatum - pB Commissura anterior, pars bulbaris - PP Paleostriatum primitivum - PPc Nucleus principalis precommissuralis - PVM Nucleus periventricularis magnocellularis - QF Tractus quintofrontalis - Rt Nucleus rotundus - SCE Stratum cellulare externum - SCI Stratum cellulare internum - SL Nucleus septalis lateralis - SM Nucleus septalis medialis - SP Nucleus subpretectalis - SPC Nucleus superficialis parvocellularis - SPM Nucleus spiriformis lateralis - SRt Nucleus subrotundus - T Nucleus triangularis - TIO Tractus isthmo-opticus - Tn Nucleus taeniae - TOv Tractus nuclei ovoidalis - TrO Tractus opticus - TSM Tractus septomesencephalicus - TT Tractus tectothalamicus - TU Nucleus tuberis - V Ventriculus     

Failure of interocular transfer in the pigeon (Columba livia).

Pigeons were trained on a modified jumping stand to discriminate a circle from a triangle using only one eye. Testing with the naive eye revealed no evidence of interocular transfer. This failure of transfer was also observed under more stringent testing using reversal learning. The results are discussed in terms of a selective attention model for panoramic vision.     

Thalamic projections to the paleostriatum and neostriatum in the pigeon (Columba livia)

Thalamic projections to the paleostriatum and neostriatum in the pigeon have been studied using wheat germ agglutinin-horseradish peroxidase in anterograde and retrograde tracing experiments. Injections centred on different mediolateral regions of the dorsal thalamus produced terminal labelling in correspondingly different mediolateral regions of the striatal complex, comprising paleostriatum augmentation and lobus parolfactorius, within the ventral paleostriatum, and within the neostriatum. Injections into various loci within these regions retrogradely labelled numerous neurons within the dorsal thalamus, the location of which varied systematically with the injection placement; and within various regions of the midbrain and pons. These experiments demonstrate a major thalamic projection to the striatum analogous to that from the midline and intralaminar nuclei to the caudatoputamen in mammals, although the patchy characteristic of mammalian striatal afferent terminations was observed only within ventral regions of the pigeon paleostriatum. In addition the experiments demonstrate that striatal afferents also originate from certain nuclei of the mesencephalic midline which are possibly equivalent to the raphe nuclei.     

Direction-selective single units in the nucleus lentiformis mesencephali of the pigeon (Columba livia)

Summary The receptive field properties of single units within the nucleus lentiformis mesencephali (LM) of the pigeon were studied using electrophysiological methods. Previous studies have suggested that the avian LM may be homologous to the nucleus of the optic tract (NOT) in mammals. Single units in the pigeon LM are similar to mammalian NOT units in that they are direction-selective, mostly for horizontal directions, velocity-selective, have large visual receptive fields and respond preferentially to large stimuli with many visual contrasts. In contrast to most reports of NOT units of mammals, more than half of pigeon LM units prefer high velocities (>10°/s), a large proportion (0.37) prefer non-horizontal directions, and receptive fields that are retinotopically arranged within the LM. The response properties of pigeon LM units are compared to the response properties of units within the accessory optic nucleus (the nucleus of the basal optic root or nBOR). In the avian brain, nBOR neurons respond at low velocities (0.5–5°/s) and respond predominantly to vertical stimulus movement whereas LM units respond over a broader range of velocities (0.2–80°/s) and respond predominantly to horizontal movements. Thus, the LM and nBOR may play different roles in the control of compensatory eye movements.This work was supported in part by PHS grant EY03638 to BJW and NSF grant BNS 8312571 to SEB     

Classical tone-shock conditioning induces Zenk expression in the pigeon (Columba livia) hippocampus

The hippocampus is involved in fear conditioning, although the molecular events underlying this function are still under investigation. The authors analyzed the expression of the Zenk proto-oncogene product within the pigeon (Columba livia) hippocampus after training with a classical aversive conditioning protocol using tone-shock associations. Control groups were trained with shock or tone alone or were only exposed to the experimental chamber and manipulated. Experimental pigeons showed significant increases of Zenk expression in the ventromedial region of the hippocampus, whereas both the experimental and shock groups had increased Zenk expression in the dorsal region. The expression of Zenk in specific neuronal populations within the pigeon hippocampus may be indicative of plasticity-associated aversive classical conditioning.     

Acute effects of light and darkness on sleep in the pigeon (Columba livia)

In addition to entraining circadian rhythms, light has acute effects on sleep and wakefulness in mammals. To determine whether light and darkness have similar effects in birds, the only non-mammalian group that displays sleep patterns comparable to mammals, we examined the effects of lighting changes on sleep and wakefulness in the pigeon. We quantified sleep behavior (i.e., bilateral or unilateral eye closure) in pigeons maintained under a 12:12 LD cycle, and immediately following a change from a 12:12 to a 3:3 LD cycle. During both LD cycles, sleep was most prevalent during dark periods. During the 3:3 LD cycle, darkness had the greatest sleep promoting effect during the hours corresponding to the subjective night of the preceding 12:12 LD cycle, whereas light suppressed sleep across circadian phases. As previously suggested, the light-induced decrease in sleep in the subjective night might be partly mediated by the suppression of melatonin by light. Although the sleep promoting effect of darkness was modulated by the circadian rhythm, sleep in darkness occurred during all circadian phases, suggesting that darkness per se may play a direct role in inducing sleep. In addition to the effects of lighting on behavioral state, we observed an overall bias toward more right eye closure under all lighting conditions, possibly reflecting a response to the novel testing environment.