Visual wulst influences on flash evoked responses in the ectostriatum of the zebra finch

Engelage J, Bischof H-J. Visual wulst influences on flash evoked responses in the ectostriatum of the zebra finch. Brain Research. 1994;652(1):17-27.Anatomical data suggest that visual information from the thalamofugal pathway contributes to visual processing in the tectofugal pathway. We addressed the question of the functionality of anatomically described connections to the visual system of a laterally eyed bird, the zebra finch. The study shows the contribution of visual wulst efferents to visual processing in the ectostriatum by recordings of visually evoked slow field potentials. Suppression of visual wulst activity resulted in a selective reduction of distinct potential components in contralaterally evoked slow field potentials. A clear reduction was observed in the maximum amplitude of short latency components in the negative wave. Long latency components of the negative wave and the entire positive wave of the contralaterally flash evoked potentials were almost abolished. Ipsilateral visual evoked potentials (VEPs) were not significantly affected. Cooling and spreading depression of the optic tectum resulted in a uniform amplitude reduction of the negative wave. The positive wave was almost abolished. Ipsilateral VEPs disappeared completely during suppression of optic tectum activity. The results showed that the visual wulst has a significant, most likely facilitatory, influence on the processing of contralateral visual information in the ectostriatum. Ipsilateral stimulus processing was partly independent from visual wulst activity. A model for thalamo- and tectofugal connectivity in the ectostriatum is suggested

The sensitive period for the morphological effects of monocular deprivation in two nuclei of the tectofugal pathway of zebra finches

Herrmann K, Bischof H-J. The sensitive period for the morphological effects of monocular deprivation in two nuclei of the tectofugal pathway of zebra finches. Brain Research. 1988;451(1-2):43-53.Previous experiments with 2-deoxyglucose (2-DG) suggested the existence of a critical previous termperiodnext term for the effects of monocular deprivation in the nucleus rotundus of zebra finches. The present study concerns the time course of this sensitive period for the morphological effects of monocular deprivation in two areas of the tectofugal visual pathway of zebra finches, the nucleus rotundus of the thalamus and the telencephalic ectostriatum. Cell size and volume changes were measured in birds subjected to 40 days of unilateral eye closure starting at ages spaced regularly throughout the first 70 days of life. The results show that monocular deprivation markedly affects cell size in both areas if the treatment starts at one or 10 days posthatch. The differences between deprived and non-deprived neurons decline monotonically with increasing visual experience prior to deprivation. However, deprivation onset at day 40 again causes as severe effects as early monocular closure. Deprivation as from day 50 or later no longer leads to abnormalities. The measurements of the volume of the nucleus rotundus parallel the cell size measurements, with the exception that the second increase in sensitivity occurs with deprivation onset at day 50 instead of day 40. These data indicate that the time course of the sensitive period for the effects of monocular deprivation may be double-peaked: the sensitivity for external stimuli declines from hatch until day 30, but has another peak at 40–50 days of life. The definite end of the sensitive period, as determined with this method, can therefore be assumed to be at around day 50–60

Phase specific morphological changes induced by social experience in two forebrain areas of the zebra finch

Rollenhagen A, Bischof H-J. Phase specific morphological changes induced by social experience in two forebrain areas of the zebra finch. Behavioural Brain Research. 1994;65(1):83-88.We examined the changes of spine density in Golgi preparations of two different areas of the forebrain of the zebra finch, the ANC (Archi-Neostriatum caudale) and MNH (medial Neo-Hyperstriatum) during development, after transferring male birds from isolation to a social condition (exposure to a female for 1 week), and after a second isolation period. MNH and ANC are two of four brain regions which are strongly activated if a male bird is exposed to a female after some time of isolation. The results of our study can be summarized as follows. 1: a peak-decline trend is observed in ANC, but not in MNH. 2: rearing conditions do not affect the development of both areas until day 70. 3: from 80 days of age, isolation leads to reduced spine density within ANC, but to enhanced spine density within MNH. 4: short social contact after isolation diminishes or eliminates the effects of isolation by an enhancement of spine density in ANC and a reduction of spine density within MNH. 5: the effects of short social rearing after isolation are reversible within ANC, but not within MNH. We presume that the alterations of spine density, which are induced by changes in social conditions, are restricted to ages older than 70 days by hormonal factors. We propose that the complexity of the ANC neuronal net follows the complexity of the social environment, and that the level of arousal is the most important factor influencing the complexity. We further suppose that the reduction of spines within MNH is the anatomical manifestation of an imprinting process, which has been shown to occur in the same experimental situation as we used it in our study

Stabilization of sexual preferences by sexual experience in male zebra finches, taeniopygia guttata castanotis

Bischof H-J, Clayton N. Stabilization of sexual preferences by sexual experience in male zebra finches, taeniopygia guttata castanotis. Behaviour. 1991;118(1):144-154.Male zebra finches, Taeniopygia guttala castanotis, were normally-raised by zebra finches or were cross-fostered to Bengalese finch, Lonchura striata, foster-parents until 40 days of age. Following isolation until day 100, half the birds in each group were housed with a zebra finch female for seven days, isolated for three days and then housed with a Bengalese finch female for seven days. The other birds were exposed to females in the reverse order. Subsequent double-choice tests showed that all the normally-raised birds preferred zebra finch females whereas the preference of cross-fostered males depended on the order of exposure to the two females: those exposed first to a Bengalese finch female preferred Bengalese finch females whereas of those exposed first to a zebra finch female, some preferred zebra finches, some preferred Bengalese finches and some showed no marked preference for either female. In order to examine the question of why the latter group showed such markd individual variation in their sexual preferences, a further group of males were cross-fostered to Bengalese finches and exposed to a zebra finch female and then to a Bengalese finch female and their behaviors were observed from day 21 until day 40 and for the two, seven-day periods with the females. The results showed that, when comparing brothers within clutches, the one that begs and is fed more by its foster-parents develops a stronger preference for Benglese finch females and that the more song phrases a male directs to the zebra finch female during the first seven-day period, the stronger the sexual preference for zebra finch females in the double-choice tests. Hence, our results confirm and extend those of IMMELMANN et al. (1991) and KRUIJT and MEEUWISSEN (1991) that sexual imprinting may be a two step process. As a first step, information about the parents is learned during a sensitive period early in life. In a second step, this information has to be tested for its validity for the selection of a sexual partner during first courtship encounters. It is the second step where the previously stored information is stabilized in memory. Giving conflicting information during the first and the second step, one can show that interactions between the young male and its parents as well as with the first sexual partner influence the final preference it shows in subsequent double choice tests

Isolation-dependent enhancement of 14C-2-deoxyglucose uptake in the forebrain of zebra finch males

Bischof H-J, Herrmann K. Isolation-dependent enhancement of 14C-2-deoxyglucose uptake in the forebrain of zebra finch males. Behavioral and Neural Biology. 1988;49(3):386-397.In a previous study (H. J. Bischof and K. Herrmann (1986), Behavioral Brain Research, 21, 215-221) we demonstrated that four forebrain areas of the zebra finch male are activated in situations which arouse the animal, for example when the birds are chased around the cage or when they are exposed to a female. These areas, the hyperstriatum accessorium-dorsale (HAD), a part of the medial neo-hyperstriatum (MNH), the lateral neo-hyperstriatum (LNH), and a portion of the caudal archi-neostriatum (ANC), show enhanced 2-[14C]deoxyglucose (2-DG) uptake according to the experimental situation. On the basis of these experiments, we examined whether the activation of the areas is correlated with motor activity and is influenced by different isolation times prior to a 2-DG experiment, where courtship of the male birds is elicited by exposing them to a female zebra finch. For this purpose, we isolated male zebra finches for 1 day, 1 week, or 8 weeks, respectively, before we injected the 2-DG and exposed the birds to a female. During the experiment, besides other activities, the number of song motifs performed by the bird and the frequency of changing perches was recorded. Our experiments demonstrate that there is a weak negative correlation between motor activity and 2-DG uptake, and a positive correlation between isolation time and 2-DG uptake. We suggest that long isolation blocks courtship behavior by some unknown mechanisms, and that the "internal drive" of the animal, which possibly corresponds with the activity of the four forebrain areas, is enhanced by isolation and by the fact that the birds do not perform the consummatory behavior. Our results also demonstrate that the 2-DG method can show up small differences in the internal state of an animal, which cannot easily be detected by behavioral measurements

Activation Changes in Zebra Finch (Taeniopygia guttata) Brain Areas Evoked by Alterations of the Earth Magnetic Field

Keary N, Bischof H-J. Activation Changes in Zebra Finch (Taeniopygia guttata) Brain Areas Evoked by Alterations of the Earth Magnetic Field. PLoS ONE. 2012;7(6): e38697.Many animals are able to perceive the earth magnetic field and to use it for orientation and navigation within the environment. The mechanisms underlying the perception and processing of magnetic field information within the brain have been thoroughly studied, especially in birds, but are still obscure. Three hypotheses are currently discussed, dealing with ferromagnetic particles in the beak of birds, with the same sort of particles within the lagena organs, or describing magnetically influenced radical-pair processes within retinal photopigments. Each hypothesis is related to a well-known sensory organ and claims parallel processing of magnetic field information with somatosensory, vestibular and visual input, respectively. Changes in activation within nuclei of the respective sensory systems have been shown previously. Most of these previous experiments employed intensity enhanced magnetic stimuli or lesions. We here exposed unrestrained zebra finches to either a stationary or a rotating magnetic field of the local intensity and inclination. C-Fos was used as an activity marker to examine whether the two treatments led to differences in fourteen brain areas including nuclei of the somatosensory, vestibular and visual system. An ANOVA revealed an overall effect of treatment, indicating that the magnetic field change was perceived by the birds. While the differences were too small to be significant in most areas, a significant enhancement of activation by the rotating stimulus was found in a hippocampal subdivision. Part of the hyperpallium showed a strong, nearly significant, increase. Our results are compatible with previous studies demonstrating an involvement of at least three different sensory systems in earth magnetic field perception and suggest that these systems, probably less elaborated, may also be found in nonmigrating birds

Functional and antigenic properties of GlpO from Mycoplasma mycoides subsp. mycoides SC: characterization of a flavin adenine dinucleotide-binding site deletion mutant

L-α-glycerophosphate oxidase (GlpO) plays a central role in virulence of Mycoplasma mycoides subsp. mycoides SC, a severe bacterial pathogen causing contagious bovine pleuropneumonia (CBPP). It is involved in production and translocation of toxic H2O2 into the host cell, causing inflammation and cell death. The binding site on GlpO for the cofactor flavin adenine dinucleotide (FAD) has been identified as Gly 12−Gly13−Gly 14−Ile15−Ile16−Gly 17. Recombinant GlpO lacking these six amino acids (GlpOΔFAD) was unable to bind FAD and was also devoid of glycerophosphate oxidase activity, in contrast to non-modified recombinant GlpO that binds FAD and is enzymatically active. Polyclonal monospecific antibodies directed against GlpOΔFAD, similarly to anti-GlpO antibodies, neutralised H2O2 production of M. mycoides subsp. mycoides SC grown in the presence of glycerol, as well as cytotoxicity towards embryonic calf nasal epithelial (ECaNEp) cells. The FAD-binding site of GlpO is therefore suggested as a valuable target site for the future construction of deletion mutants to yield attenuated live vaccines of M. mycoides subsp. mycoides SC necessary to efficiently combat CBPP

Encoding of naturalistic optic flow by motion sensitive neurons of nucleus rotundus in the zebra finch (TaeniopygiaTaeniopygia guttataguttata)

Eckmeier D, Kern R, Egelhaaf M, Bischof H-J. Encoding of naturalistic optic flow by motion sensitive neurons of nucleus rotundus in the zebra finch ($Taeniopygia$ $guttata$). Frontiers in Integrative Neuroscience. 2013;7:68.The retinal image changes that occur during locomotion, the optic flow, carry information about self-motion and the three-dimensional structure of the environment. Especially fast moving animals with only little binocular vision depend on these depth cues for maneuvering. They actively control their gaze to facilitate perception of depth based on cues in the optic flow. In the visual system of birds, nucleus rotundus neurons were originally found to respond to object motion but not to background motion. However, when background and object were both moving, responses increased the more the direction and velocity of object and background motion on the retina differed. These properties may play a role in representing depth cues in the optic flow. We therefore investigated, how neurons in nucleus rotundus respond to optic flow that contains depth cues. We presented simplified and naturalistic optic flow on a panoramic LED display while recording from single neurons in nucleus rotundus of anaesthetized zebra finches. Unlike most studies on motion vision in birds, our stimuli included depth information. We found extensive responses of motion selective neurons in nucleus rotundus to optic flow stimuli. Simplified stimuli revealed preferences for optic flow reflecting translational or rotational self-motion. Naturalistic optic flow stimuli elicited complex response modulations, but the presence of objects was signaled by only few neurons. The neurons that did respond to objects in the optic flow, however, show interesting properties

Light-dependent magnetoreception in birds: increasing intensity of monochromatic light changes the nature of the response

BACKGROUND: The Radical Pair model proposes that magnetoreception is a light-dependent process. Under low monochromatic light from the short-wavelength part of the visual spectrum, migratory birds show orientation in their migratory direction. Under monochromatic light of higher intensity, however, they showed unusual preferences for other directions or axial preferences. To determine whether or not these responses are still controlled by the respective light regimes, European robins, Erithacus rubecula, were tested under UV, Blue, Turquoise and Green light at increasing intensities, with orientation in migratory direction serving as a criterion whether or not magnetoreception works in the normal way. RESULTS: The birds were well oriented in their seasonally appropriate migratory direction under 424 nm Blue, 502 nm Turquoise and 565 nm Green light of low intensity with a quantal flux of 8·10(15 )quanta s(-1 )m(-2), indicating unimpaired magnetoreception. Under 373 nm UV of the same quantal flux, they were not oriented in migratory direction, showing a preference for the east-west axis instead, but they were well oriented in migratory direction under UV of lower intensity. Intensities of above 36·10(15 )quanta s(-1 )m(-2 )of Blue, Turquoise and Green light elicited a variety of responses: disorientation, headings along the east-west axis, headings along the north-south axis or 'fixed' direction tendencies. These responses changed as the intensity was increased from 36·10(15 )quanta s(-1 )m(-2 )to 54 and 72·10(15 )quanta s(-1 )m(-2). CONCLUSION: The specific manifestation of responses in directions other than the migratory direction clearly depends on the ambient light regime. This implies that even when the mechanisms normally providing magnetic compass information seem disrupted, processes that are activated by light still control the behavior. It suggests complex interactions between different types of receptors, magnetic and visual. The nature of the receptors involved and details of their connections are not yet known; however, a role of the color cones in the processes mediating magnetic input is suggested

Neurite Outgrowth of Mature Retinal Ganglion Cells and PC12 Cells Requires Activity of CK1δ and CK1ε

Mature retinal ganglion cells (RGCs) do not normally regenerate severed axons after optic nerve injury and show only little neurite outgrowth in culture. However, RGCs can be transformed into an active regenerative state after lens injury (LI) enabling these neurons to regrow axons in vitro and in vivo. In the current study we investigated the role of CK1δ and CK1ε activity in neurite outgrowth of LI stimulated RGCs and nerve growth factor (NGF) stimulated PC12 cells, respectively. In both cell types CK1δ and ε were localized in granular particles aligned at microtubules in neurites and growth cones. Although LI treatment did not measurably affect the expression of CK1δ and ε, it significantly elevated the specific kinase activity in the retina. Similarly, CK1δ/ε specific kinase activity was also elevated in NGF treated PC12 cells compared with untreated controls. Neurite extension in PC12 cells was associated with a change in the activity of CK1δ C-terminal targeting kinases, suggesting that activity of these kinases might be necessary for neurite outgrowth. Pharmacological inactivation of CK1δ and ε markedly compromised neurite outgrowth of both, PC12 cells and LI stimulated RGCs in a concentration dependent manner. These data provide evidence for a so far unknown, but essential role of CK1 isoforms in neurite growth