Flight effects on plasma levels of neurohypophysial hormones in homing pigeons

A significant increase in the circulating levels of arginine vasotocin (AVT), without change in plasma osmolality, was observed in homing pigeons immediately after a flight of 48 km, lasting 60-80 min. This increase in plasma AVT is perceived as part of an overall homeostatic mechanism of mobilizing lipid as fuel for the flight muscles, of water conservation and temperature regulation in the body during the homing flight within the specific distance and duration of flight and under normal weather conditions. However, there was no change in plasma levels of mesotocin (MT) which suggests that the birds were under no significant stress during the flight.

Enhancement and suppression in the auditory midbrain nucleus (MLD) of the pigeon

Auditory evoked potentials (AEPs) and spike responses were recorded from the same recording site in the nucleus mesencephalicus lateralis pars dorsalis (MLD) in pigeons with a tungsten microelectrode. Depending on the recording sites within the MLD, enhancement and suppression of the AEPs in response to clicks were observed at particular frequencies of a background continuous pure tone. Post stimulus time histograms (PSTs) of the spike responses, if available in such cases, were recorded from the same position by the same electrode. Suppression of the AEPs always occurred but enhancement occurred in only 21% of the trials. The frequencies of tone bursts that caused maximum AEP were vaguely related to the frequencies of continuous pure tones that elicited maximum suppression of the AEPs in response to clicks. However, enhancement was produced by a continuous pure tone of approximately 1.5 kHz, independent of the frequencies of tone bursts that produced maximum AEPs. Most of the PSTs in such instances showed parallel relations between the spike responses and the amplitudes of the AEPs. The nature of the enhancement and suppression of the click evoked AEPs during continuous pure tones was clearly different from those in recordings from the nucleus magnocellularis, nucleus angularis and Field L in respect to the probability of occurrence of enhancement and suppression.

Thyroid and adrenal function in the ring dove (Streptopelia risoria) during food deprivation and a breeding cycle

The concentration of plasma triiodothyronine (T3), thyroxine (T4), corticosterone, and glucose as well as body weight and food intake were measured in pairs of ring doves throughout a breeding cycle and during food deprivation. During courtship and incubation the levels of plasma T4 were significantly higher in males than in females. A transitory decrease in food intake in both sexes was measured at the onset of incubation but was not associated with a change in body weight or in levels of plasma thyroid hormones. After the eggs had hatched, food intake increased but was associated with a reduction in body weight and concentrations of plasma T3 and T4, although plasma corticosterone and glucose both increased. Food deprivation for 48 hr resulted in a significant fall in the concentration of plasma T3 and an increase in plasma corticosterone. These changes suggest that all the food was not being digested by the adult birds during brooding but was almost exclusively regurgitated to feed the squabs.

Time to collision is signalled by neurons in the nucleus rotundus of pigeons

Throughout the animal kingdom, the sight of a rapidly approaching object usually signals danger and elicits an escape response. Gibson suggested that the symmetrical expansion of an object's image (looming) is the critical variable determining that the object is on a collision course with the observer. Similarly, large expanding flow-fields like those produced by locomotion may precipitate manoeuvres such as turning or landing. From such observations it has been shown that the optic flow parameter, tau, which specifies time to contact with the approaching object best fits the behavioural data. We describe a subpopulation of neurons in the nucleus rotundus of the pigeon brain that respond selectively to objects moving on a collision course towards the bird.

Is visual lateralization in pigeons sex-dependent?

Adult homing pigeons (Columba livia) of both sexes were trained binocularly on a successive pattern discrimination task. After reaching criterion they performed the task on alternate sessions under monocular left or right viewing conditions. Regardless of their gender, all animals reached higher pecking scores when sight was restricted to the right eye. Due probably to a ceiling effect, the discrimination-accuracy scores did not differ between left and right condition. Thus, at least with respect to the number of responses emitted, a sex dependency of visual lateralization could not be demonstrated. The results are discussed in the light of studies which demonstrate that male and female pigeons have similar anatomical asymmetries of their optic tecta.

In vitro influence of hormones on transport of glucose and glycogen in liver and muscle of pinealectomised pigeons, Columba livia Gmellin

To substantiate the increased peripheral utilization of blood glucose by pineal in wild pigeons, an in vitro study on the ability of liver and muscle slices of intact and pinealectomised wild pigeons (C. livia) in terms of uptake and release of glucose, and deposition and depletion of glycogen, in presence of insulin, acetylcholine, glucagon and adrenaline has been undertaken. A total insensitivity of liver and muscle of pinealectomised birds for glycogen deposition and insensitivity of liver for glucose uptake has been observed. Increased glucose release from liver in response to adrenalin has been observed. The results are discussed in terms of involvement of pineal in metabolic regulation associated with breeding activities.

Hippocampal lesions impair navigational learning in experienced homing pigeons

Adult experienced homing pigeons from Maryland were subjected to hippocampal lesion and then transferred to a new loft in Ohio to examine what effect such treatment may have on learning to navigate to a new home loft. When subsequently released from an unfamiliar site, the hippocampal lesioned birds were impaired in taking up a vanishing bearing toward their new Ohio loft. This deficit is interpreted as an impairment in hippocampal-lesioned birds learning a new navigational map. Together with a previous study, the results suggest that an intact hippocampus is necessary if young naive or adult experienced homing pigeons are to learn a navigational map.

[The spatial frequency limits and the resolving power of the visual system of the pigeon]

The spatial contrast transfer function of the visual system of the pigeon was determined by recording from the optic tectum evoked potentials or extracellular unit activity in response to a pattern stimulus contrast transfer function, determined as a "response function", describes the relationship between the contrast in the pattern--which consisted of vertically oriented stripes of sinusoidally varying luminance--and the amplitude of the response at various spatial frequencies (c/deg). The transfer function yields an estimate of the high frequency limit, which in turn is a measure of visual resolving power. Action potentials were recorded extracellularly using glass microelectrodes; for evoked potentials, stainless steel electrodes were used. Recordings were made from the stratum griseum et fibrosum superficiale of the optic tectum. The highest spatial frequency detectable in a visual system is limited by various factors, including the diffraction of light at the pupil and the anatomical spacing of the photoreceptors. The pupil factor can be controlled in experiments in a suitable way. In this paper, the electrophysiologically determined high-frequency limit was compared with the theoretical resolution limit imposed by the photoreceptor mosaic. The experimental results show that the visual system of the pigeon has a high-frequency limit at a spatial frequency of 15.5 c/deg, corresponding to a visual acuity of 1.9 min of arc. The attempt to relate visual acuity in the pigeon to the anatomical spacing of the photoreceptors shows that the Nyquist frequency of the photoreceptor mosaic, the theoretical upper bound of the spatial resolution, agrees with measurement.

Role of splanchnic nerve on steroid-hormone-induced alteration of adrenomedullary catecholamines in untreated and reserpinized pigeon

The aim of the present investigation was to ascertain (1) the effect of steroid hormones (corticosterone, dexamethasone, deoxycorticosterone, progesterone, testosterone and oestrogen) on the neural regulation of adrenomedullary catecholamine (CA) content, and (2) the neural modulation of the effect of glucocorticoid hormones (corticosterone and dexamethasone) on reserpine-induced resynthesis of CA. The experiment was conducted on unilaterally splanchnic-denervated pigeons. The findings revealed that 7 consecutive days of steroid treatments (2.5 mg.kg b.w.-1, i.m.) resulted in significant changes of CA content. Interestingly, the changes of epinephrine (E) content differed significantly between the innervated and denervated glands. This clearly indicates that the splanchnic nerve regulates steroid-induced alterations of E content in the pigeon. The results further revealed that the glucocorticoid hormones augmented reserpine-induced resynthesis of CA specifically in the innervated glands. This confirms that the splanchnic nerve is essential for the synergistic action of glucocorticoids and reserpine in accelerating resynthesis of CA.

Grasping in the pigeon: control through sound and vibration feedback mediated by the nucleus basalis

Pigeons were trained to detect auditory and vibratory stimuli in two separate experiments using an instrumental conditioning procedure. The discriminative stimuli became effective as the subjects grasped a probe with the beak. The pigeons learned to suppress responding upon this grasp-contingent stimulation. Bilateral lesions of the nucleus basalis prosencephali (Bas), known to be involved in the motor control of pecking and to receive short latency input of cochlear and trigeminal origin, eliminated the behavioral stimulus detection. The performance of a control color discrimination was not affected by the Bas lesions, demonstrating that these had a specific effect. The processing of peck-related feedback by the nucleus basalis during the normal food uptake of pigeons is discussed.

Distribution and hypothalamic projection of tyrosine-hydroxylase containing neurons of the nucleus of the solitary tract in the pigeon

The avian nucleus of the solitary tract has an extensive subnuclear organization. Several subnuclear cell groups can be distinguished on the basis of cytoarchitectonic criteria. In general, the subnuclei of the medial division of the nucleus of the solitary tract receive gastrointestinal afferents, whereas the subnuclei of the lateral division of the nucleus of the solitary tract receive cardiopulmonary afferents. Forebrain afferents to the nucleus of the solitary tract are segregated to medial and lateral subnuclei, which are located at the periphery of the nucleus. These peripheral subnuclei of the nucleus of the solitary tract are also the source of ascending axonal projections to the forebrain. In this study, the tyrosine hydroxylase (initial enzyme for catecholamine synthesis) content of the anteromedial hypothalamic projecting neurons of the nucleus of the solitary tract is determined by use of a combined retrograde fluorescent dye-immunofluorescence method. Fast Blue implanted into the anteromedial hypothalamus (in the region of the nucleus periventricularis magnocellularis) resulted in the retrograde labeling of neurons in the caudal two-thirds of the nucleus of the solitary tract. At levels rostral to the obex, dye-labeled cells were mostly observed in the dorsally located subnuclei medialis superficialis pars posterior and lateralis dorsalis pars posterior and in the ventrally located subnucleus medialis ventralis pars posterior. More centrally located subnuclei contained few labeled cells, if any. For example, subnucleus medialis intermedius pars posterior only had a few retrogradely labeled cells, whereas the centrally located subnucleus medialis dorsalis pars posterior was almost devoid of labeled cells. At levels caudal to the obex, many retrogradely labeled neurons of the nucleus of the solitary tract were observed. Neurons immunoreactively labeled for tyrosine hydroxylase were mostly found within subnuclei, which contain anteromedial hypothalamic projection neurons. In subnuclei medialis superficialis pars posterior and lateralis dorsalis pars posterior, 87% of the retrogradely dye-labeled cells were also immunoreactively labeled, whereas in the caudal nucleus of the solitary tract (at levels caudal to the obex), 68% of the retrogradely labeled cells were immunoreactively labeled. Not all tyrosine hydroxylase containing cells had projections to the implantation site in the anteromedial hypothalamus since only 40% of the immunoreactive cells in the caudal nucleus of the solitary tract and 59% of the immunoreactive cells in the subnucleus medialis superficialis pars posterior were retrogradely labeled with Fast Blue.(ABSTRACT TRUNCATED AT 400 WORDS)

[The local blood flow and oxygen tension in the brain of pigeons under high-altitude hypoxia]

The effect of barochamber hypoxia on the local blood flow in the pigeon neostriatum caudalum, hypostriatum accessorium, ectostriatum, cerebellum cortex was studied by means of the hydrogen clearance technique. The hypoxia was shown to decrease the oxygen available in the brain tissue and to increase the blood flow. The changes were different in different brain structures. The spectral analysis of the oxygen available fluctuations revealed no regular changes in the temporal pattern of the fluctuations.

Passive immunization against chicken vasoactive intestinal polypeptide suppresses plasma prolactin and crop sac development in incubating ring doves

Passive immunization of incubating ring doves with daily injections of sheep anti-chicken vasoactive intestinal polypeptide (cVIP) serum prevented the proliferation of crop sac tissue observed in control doves given nonimmune serum. Daily injections of anti-cVIP serum did not prevent crop sac development in nonbreeding doves simultaneously treated with ovine prolactin. The concentrations of plasma prolactin were significantly depressed in birds given anti-cVIP serum although this effect became progressively less pronounced during the course of the 7- or 14-day treatment periods. Body weights and weights of regressed reproductive organs were unaffected by treatment with anti-cVIP serum and did not differ significantly from control birds. Doves showing a decreased prolactin response to anti-cVIP serum treatment developed an immune response to sheep serum which may have immunoneutralized the administered antibody. Concentrations of plasma LH were not consistently affected by anti-cVIP serum administration and were low throughout the study. The depression in plasma LH normally seen in females after their young hatch was not observed in females treated with anti-cVIP serum. No effect of treatment was observed upon the birds' incubation behavior or in their readiness to feed and brood their young. These results suggest that in the ring dove, VIP is the physiological prolactin-releasing factor responsible for stimulating prolactin secretion and consequently the development of the crop sac, during incubation. They further indicate that increased concentrations of plasma prolactin may not be essential for gonadal regression or the maintenance of full incubation and brooding behavior in ring doves under laboratory conditions.

The effects of phenobarbital on responding under delayed-matching-to-sample procedures with differential and nondifferential outcomes

Pigeons were exposed to delayed-matching-to-sample procedures in which food or a flash of the feeder light followed correct responses. When these consequences were correlated with a particular stimulus (e.g., food followed matching responses to red and a flash of the feeder light followed matching responses to green), accuracy was significantly higher (i.e., stimulus control was greater) than when discriminative stimuli and consequences were not correlated. Acute administrations of phenobarbital (10-40 mg/kg) produced similar effects regardless of whether or not differential outcomes were arranged for correct responses to a particular stimulus. At doses of 30 and 40 mg/kg, phenobarbital significantly decreased accuracy under both variations of the delayed-matching-to-sample procedure. Given these results, it appears that degree of stimulus control in the absence of drug did not modulate drug effects in the present study.

Energetic responses of pigeons during food deprivation and restricted feeding

Pigeons ate food ad lib, then fasted for several days, and finally ate a controlled amount of food once a day for several months to maintain body weight at 80% of the ad lib value. Whole-body dry heat loss (HL) and core body temperature (Tb) were measured continuously for each pigeon. Thermal conductance (C) was calculated from HL and Tb. Relative to ad lib feeding, 24-h HL was reduced by approximately 50% during fasting and controlled feeding. The majority of energy savings was achieved by lowering C, which appeared to maintain a saturated low value throughout most of the light and dark phases. Therefore, the pigeon's characteristic high Tb in the daily light phase during fasting and food restriction does not necessarily imply high energy expenditure. In the dark phase, the fasting pigeon's characteristically low Tb enhances energy savings already being achieved through lowered C. The daily cycle in Tb, and to a lesser extent in HL and C, was strongly altered by occasional probe variations in the amount of food given at the single daily feeding and by a shift in the time of the daily feeding.

[Effect of a passive orthostatic test on lymph circulation]

Anesthesized dogs were exposed to a 30 minute tilt test at 30 degrees. Most significant changes were seen in venous and lymphatic vessels. During the first minutes of the tilt test lymph flow from the thoracic compartment diminished rapidly and later it partially recovered. Pressure in the thoracic lymphatic duct diminished in parallel with that in the jugular vein. Lymph flow from the neck vessel at first increased and then decreased. After the animals were returned to the recumbent position, their venous and lymphatic pressure reached the pretest level. Lymph flow from the thoracic duct increased drastically and then returned to the baseline level. During moderate orthostatic effects lymph circulation undergoes significant changes produced by gravitational shifts and morphofunctional specificities of lymphatic vessels.

[Vestibular nystagmus as a result of the interactions between semicircular canals and the otolithic membrane subsystems of the vestibular system]

Untreated and treated (unilateral section of utricular and saccular branches of the vestibular nerve) pigeons Columba livia were rotated in the dark in the horizontal plane, the head being in a different position relative to the axis of rotation. The range of angular acceleration was 7-19 deg/c2 and the peak value of centrifugal acceleration was 0.5 g. The neck and eye nystagmus was recorded. It was found that: 1) the result of canal-otolith interaction was not directly related to the pattern of changes of otolith afferentation but was determined by the ratio of otolith afferent signals in the right and left labyrinths and, consequently, by the ratio of patterns of activities in the CNS paired structures that receive otolith afferentation; 2) the same result of interaction (enhancement or attenuation of vestibular responses) can be achieved through both increase or decrease of otolith afferentation; 3) if joint stimulation of semicircular canals and otolith organs induces asymmetry of neuronal activities of paired brain structures that perceive otolith afferentation, then, irrespective of the mechanism of origin of this asymmetry, it is followed by changes of oppositely directed nystagmus of different sign (increase for one nystagmus and decrease for the other). It is concluded that the symmetry of reactions recorded in response to isolated stimulation of semicircular canals (otolith organs) cannot be considered as a reliable criterion of functional symmetry of semicircular canals (otolith organs).

Neural influence on oxytocin-induced changes of adrenomedullary catecholamines in the pigeon

Oxytocin (0.25 IU/100 g body wt) was injected intraperitoneally only once to unilaterally splanchnic denervated pigeons. The effects were investigated after 0.5, 4, 12, 24, 72, 144 and 216 h of administration. The findings revealed that oxytocin caused the release of more norepinephrine (NE) from the denervated glands up to 24 h after treatment. In contrast, oxytocin-induced release of epinephrine (E) showed no significant difference in between the innervated and the denervated glands after 0.5 h of treatment. Strikingly, oxytocin brought about release of more E from the denervated glands after 24 h of treatment. This indicates that the first phase of NE release and the second phase of E release are neurally regulated. The findings further revealed that the resynthesis of both NE and E was faster in the innervated glands after 216 h of oxytocin treatment. This clearly points out that the splanchnic nerve accelerates resynthesis of both NE and E induced by oxytocin.

Effects of unilateral thalamic lesion upon interocular transfer of visual discrimination in pigeons. II: Lesion in the untrained hemisphere (sensory deficits)

In a previous study, rotundal lesions in the 'trained' hemisphere caused deficits in interocular transfer of visual discrimination when the lesion was made after acquisition of the monocular learning, but not when the lesion was made before the monocular learning. In the present study, a rotundal lesion was made in the 'untrained' hemisphere before and after monocular training. The lesion caused deficits in transfer regardless of the temporal relation between the lesion and the training. Such deficits are likely to be 'sensory deficits' since visual information from the eye goes to the damaged rotundus when tested with the untrained eye. The relation between the 'sensory' versus 'mnemonic' deficits from damage to nucleus rotundus in the trained hemisphere are discussed.

Retinal afferents to the tectum opticum and the nucleus opticus principalis thalami in the pigeon

The retinal afferents of the tectum opticum and the n. opticus principalis thalami (OPT) were studied with fluorescent tracers in pigeons. Injections into the tectum opticum revealed topographically related areas of high density labelling in the contralateral retina. In these areas up to 15,000 cells/mm2 were labelled. After tectal injections the soma sizes of labelled retinal ganglion cells in the area centralis ranged from 5 to 23 microns with a mean of 7.5 microns. Afferents from the ipsilateral retina could not be demonstrated. Injections into the OPT labelled neurons throughout the retina without a clear topographical relation to the locus of injection. The density never exceeded 150 cells per mm2. The soma size range was 8 to 35 microns with a mean of 14.6 microns. Independently of the injection area within the OPT, the red field in the dorsotemporal retina was always extremely sparsely labelled. The number of labelled ganglion cells in this area never exceeded 25 neurons/mm2. After OPT injections the average density of labelling per unit area was six times higher in the yellow than in the red field. The results confirm previous reports of a massive and topographically organized retinal projection onto the optic tectum. The projection onto the OPT was clearly smaller and with the retrograde tracing techniques in use, an orderly topography has not been demonstrated. The paucity of red field projections onto the OPT suggests that the role of the thalamofugal pathway in binocular integration is very limited.

[Relative numerousness judgements in crows and pigeons in the urgent comparison of stimuli earlier linked to different amounts of reinforcement]

The ability of pigeons (Colomba livia, L.) and crows (Corvus corone cornix, L.) was studied to realize urgent numerousness judgement of reinforcement consisting of discrete elements (wheat grains and meal worm larvae, respectively). In the process of preliminary training the birds mastered the information about the conformity of the feeder colour with the definite number (1-9 for pigeons and 5-12 for crows) of reinforcement units at isolated presentation of feeders. In test at presentation of pairs formed from these feeders, pigeons and crows chose the stimulus connected with a greater quantity of reinforcement. In the range of 1-8 units the precision of choice in pigeons depended on absolute and relative differences between comparing values. In crows in the range of 6-12 this dependence was not revealed. The ability to solve the given test is considered as one of manifestations of elementary reasoning.

Olfactory cues perceived at the home loft are not essential for the formation of a navigational map in pigeons

Deflector lofts consist of a ‘pinwheel’ arrangement of four stationary deflector panels attached to the sides of a cube-shaped cage. These panels are made of wood and Plexiglas and rotate incoming winds in either a clockwise or counterclockwise direction. When released at a distant site, homing pigeons (Columbia livia) raised in deflector lofts exhibit a shift in orientation relative to controls which corresponds to the clockwise or counterclockwise rotation of winds in their loft, suggesting the involvement of wind-borne olfactory cues in pigeon navigation. As part of a long-term study designed to test whether orientation cues other than odors might also be involved in creating the deflector-loft effect, we carried out experiments in upstate New York, USA, in which deflector lofts were modified to reverse the direction of light reflected from the Plexiglas panels while leaving the rotation of winds unchanged. The results indicate that the orientation of pigeons raised as permanent residents of these altered deflector lofts is not influenced by reflected light cues; i.e. they exhibit the same orientation bias as birds raised in the lofts with normal panels. This is in direct contrast to our previous findings that non-resident pigeons kept in the altered lofts for short periods exhibit a reversal of initial orientation compared to birds from the lofts with normal panels. However, when permanent-resident birds are prevented from having a direct view of the horizon sky by the addition of ‘anti-cheating’ slats (which prevent the birds from seeing beyond the end of each panel), the deflections are either greatly reduced or eliminated entirely, contrary to the predictions of olfactory navigation models. This disappearance of the deflector-loft effect in the presence of anti-cheating slats suggests that the positions of the deflector panels in the two experimental lofts must be differentially influencing important visual orientation cues reaching the birds housed inside. We believe that these cues are probably derived from polarized skylight emanating from the horizon, and that the obstruction of specific regions of horizon skylight by the deflector panels in the two experimental lofts is responsible for a miscalibration of the pigeon's sun compass. This miscalibration, in turn, generates the orientation bias observed for deflector-loft birds. Our findings force us to conclude that, at least for pigeons raised in New York (and perhaps those from other geographical locations as well), olfactory cues perceived at the home loft do not contribute to the formation of the navigational map.