Age dynamics of visually guided behavior and visual evoked potentials of altricial nestlings

Comparative study has been carried out of factors of organization of visually guided feeding behaviour (observation method) and the degree of maturity of the visual mechanisms by the criterion of Wulst EPs formation and of their recovery cycles in normally developing and visually deprived nestlings. In has been established that during the period following the opening of the eyes (5-9th day) the feeding behaviour is connected with diffuse photo-sensitivity of visual mechanisms. Diffuse photo-sensitivity fully provides for natural feeding behaviour at the corresponding stage of development of visual functions. Complete visual deprivation during the whole period of diffuse photo-sensitivity does not influence subsequent development of the visual system.     

Role of a species-specific acoustic environment in the development of hearing in nestlings

Main parameters were studied of the acoustic evoked potentials (EPs) from L field of the caudal neostriatum of altricial nestlings of 2-8 days to pure tones in the range of species-specific signals. It has been established that auditory EPs to the tones of different frequencies differ by the terms of appearance and the degree of maturity. At every of the revealed stages of the auditory ontogenesis, including the stage of completely formed auditory sensitivity, such parameters of auditory EPs, as latencies of different phases, amplitude-temporal pattern and the course of recovery curve are different for the tones of different frequencies. The earliest to appear are the responses to the tones 0.2-4.0 kHz, corresponding to the energy of alimentary signals. Responses to tones of higher frequencies corresponding to the spectrum of other species-specific signals appear later, but the speed of their formation is higher than in the responses to the tones of low frequencies. It is suggested that the higher speed of sensitivity maturation in the high-frequency region is determined by ecologically conditioned afferentation, the function of which is fulfilled by nestlings own vocalization.     

Relation between the defensive behavior of altricial nestlings and the parameters of an alarm signal. Neuroethologic approach

The acoustic organization of the defensive behaviour was studied in Pied Flycatcher nestlings. Electrodes were chronically implanted into the field L and the neck muscles for auditory EPs and EMG recordings. A well developed defensive reaction which under natural conditions is elicited by species-specific alarm call, could be artificially provoked by monotonal 4.5-6 kHz bursts with repetition frequency of 4-0,8/s. The tone frequency was shown to be the critical acoustic parameter permitting the altricial nestlings to identify alarm vocalization and differentiate it from alimentary signals. The role of the burst repetition frequency is restricted to maintaining the tonic defensive activation in the course of the alarm signal presentation. Certain correlation was found between the time of regeneration of excitability in auditory structures and the burst repetition frequency in the species specific alarm signal.     

The effect of acute alcohol administration on auditory evoked potentials in altricial nestlings during the development of natural behavior]

Acute ethanol influence on field L auditory evoked potentials (AEP) was studied in 4-8-days-old altricial nestlings of pied flycatcher. Nestlings were presented with tone pips related with the realization of natural behaviour (2.0 and 5.0 kHz) and bearing no meaning for the behaviour of the young of the age under study (3.0 kHz). Ethanol ingestion was found to reduce the maturity index (MI) of AEP in response to "behavioural" but not to control frequencies; this effect was first observed at day 5, when nestlings eyes opened and defence behaviour appeared, while previously formed feeding behaviour was significantly modified. During the next 2 days alcohol had a greater effect upon the AEP in response to 2.0 kHz tone pips, related with feeding behaviour of increasing complexity than upon the AEP in response to 5.0 kHz, related with the defence behaviour that remained relatively constant. The previous data concerning the effect of alcohol on unit activity are used to support the view that MI increase during the early postembryonic ontogeny is due to the involvement of neurons with newly formed behavioural specializations into the subserving of new behavioural patterns while the decrease of MI under alcohol is due to the depression of activity in these neurons.     

Increasing selectivity of defense behavior during development of pied flycatcher nestlings

The development of defense reaction was studied in the wildlife and experimentally in 7 broods of altricial pied flycatcher (Ficedula hypoleuca) nestlings. Field studies demonstrated that passive-defense response first appeared on the 4th day of the nest life. It developed from the cessation of begging in young relatively satiated nestlings to characteristic freezing response independent of the level of feeding motivation in older nestlings. Older nestlings also acquire the defense reaction in response to novel visual stimuli. The efficiency of the natural stimulus for defense behavior (species-specific alarm call) nongradually changes during the nest life attaining the 100% level only on the 11th posthatching day. During the initial phase of defense behavior development, the reaction can be induced by different rhythmically organized stimuli. Later it becomes considerably more selective and other rhythmic and acoustic signals become much less effective than the alarm call.     

Development of the auditory sensitivity and formation of the acoustically guided defensive behavior in nestlings of the pied flycatcher Ficedula hypoleuca

Age dynamics of generation of the evoked potentials (EP) in the field L of caudal nidopallium (the higher integrative center of the avian auditory system) and development of the auditory-guided defensive behavior were studied in control and visually deprived pied flycatcher Ficedula hypoleuca nestlings. It was shown that the rhythmically organized monofrequency signals with sound frequency 3.5 kHz and higher produced the defensive behavior as the auditory sensitivity to these frequencies matured. After 9 days, the species-specific alarm signal produced more effectively the defensive behavior than the tonal signals. The rhythmically organized sound with filling frequency 0.5 kHz, occupying the less low-frequency diapason than the feeding signal, produced the effect opposite to the alarm signal to increase the nestling mobility. At the initial stage of the defensive behavior development the auditory threshold fell markedly in the frequency diapason corresponding to the frequency diapason of the alarm signal (5–6 kHz), which seemed to facilitate involvement of this diapason signals in the defensive integration. The auditory EP generation thresholds in the whole studied diapason were lower in the visually deprived nestlings than in the normally developing one; however, the ability of the acoustic signals to suppress alimentary reactions fell significantly.     

Functional aspects of evoked alpha and theta responses in humans and cats

A systems theoretical approach was used to compare possible functional roles of theta (4--7 Hz) and alpha (8--15 Hz) response components of brain evoked potentials. These response components were described earlier by Ba\c sar (1980). We recorded EEG and evoked potentials (EPs) from occipital scalp locations in 11 subjects. We used auditory and visual stimuli as inadequate and adequate stimuli, respectively (``cross-modality' measurements). The combined EEG-EP epochs were analysed in frequency domain with fast Fourier transform and adaptive digital filters. Alpha (8--15 Hz) response components turned out to be dependent on whether the stimulus was adequate or not (median amplitude with inadequate vs. adequate stimulation: vs. ). Theta (4--7 Hz) response components were less dependent on stimulus modality (inadequate vs. adequate stimulation: vs. ). In EP recordings the occipital alpha response almost disappeared in the first 250 ms following auditory stimulation. Comparable behaviour was observed in similar experiments with recordings from the cat visual cortex (area 17) and with occipital magnetoencephalographic recordings. Taking into account the above-mentioned previous reports on intracranial recordings in primary sensory areas of the cat brain and preliminary results of magnetoencephalographic measurements, we propose the following hypothesis: alpha responses in a time window of about 250 ms after stimulation might predominantly reflect primary sensory processing whereas the theta responses in the first 250 ms after stimulation might be more involved in supra-modality -- or cross-modality -- associative-cognitive processing. Received: 25 February 1994 / Accepted in revised form: 5 August 1994     

The role of visual afferentation in the development of early defense behavior of pied flycatcher nestlings

The development of defense behavior in normal and visually deprived pied flycatcher nestlings was studied in the wild. It was demonstrated that the young deprived of the visual afferentation did not develop the freezing posture. In the majority of cases, specific alarm call suppressed begging in visually deprived nestlings less effectively than in the control ones. Visually deprived nestlings could not discriminate between the alarm call and other rhythmically organized acoustic signals even though the latter effectively suppressed begging.     

Signalling of Nutritional Need by Magpie Nestlings

The relationship between begging behaviour, chick nutritional state, and parental distribution of food within broods was studied in 4- and 5-chick magpie Pica pica broods under natural conditions. Three components of the begging display (duration, latency, and posture) were highly correlated with each other and also with the emission and duration of begging calls. Begging performance was strongly influenced by the food intake of nestlings during the preceding 1-h interval, indicating that begging may reliably reflect the nutritional need of nestlings. Daily growth during the preceding day, as well as average cumulative food intake by the brood during the preceding 24 h, seemed not to affect begging in a similar way. Begging signals employed by hungrier nestlings involved a higher degree of muscular activity, thus supporting the prediction that nestlings in greater need should employ more costly signals. Overall, those nestlings who begged more tended to obtain more food, but the relationship between feeding success and begging behaviour was weak due to a high variation between broods in the way that parents seemed to respond to variations in begging behaviour. Possible causes for this variation, and its implications for the evolution of reliable begging displays, are discussed.     

Natural 1st and 2d degree conditioned food reflexes in the dog in relation to space orientation

In three dogs formation and performance of spatial alimentary natural conditioned responses of the second order was studied when the dog had to find food preliminarily shown to it in one of the four food-distributors (psychonervous activity directed by a food image in terms proposed by I. S. Beritashvili). Characteristics of this form of behaviour were demonstrated and discussed: rapid formation, dependence of performance on the delay time, conflict between responses of the first and the second order. In the second series of the experiments food-procuring behaviour of dogs was studied under conditions of conflict between the quality (value) of alimentary reinforcement and probability of its finding in certain food-distributor. Such kind of behavior was shown to depend on the motivation level and individual characteristics of the dog. Interaction of "informational" (anterior areas of the neocortex, hippocampus) and "motivational" (nuclei of amigdalar complex, hypothalamus) cerebral structures is supposed to underlie the organization of behaviour.     

Establishment of the afferent function of the striatum in the rabbit during early ontogenesis

The study is dedicated to electrophysiological analysis of development of the caudate nucleus afferent function in rabbits in early postnatal ontogenesis. By amplitude-temporal parameters of the evoked potentials (EPs) of the caudate nucleus, recorded in response to stimulation of afferent inputs from the cortical regions (motor and limbic) and substantia nigra, similar dynamics of these afferent pathways functional maturation is revealed from the beginning of functioning (in the age of 3-5 days) to the definitive level (by the 30th day of life). The most significant changes of the amplitude-temporal parameters of the evoked potential, particularly of latencies are observed during the 3d week of postnatal life. On the basis of the obtained data, the conclusion is made on the formation of a common system of striatum sensory integration in the 3d-4th week of rabbits life. This age period is considered as critical.     

Food availability and the male's role in parental care in double-brooded Treecreepers Certhia familiaris

The aim of this work was to examine differences in paternal and maternal care in a double-brooded, monogamous species, the Treecreeper Certhia familiaris, in relation to food availability. As a measure of parental care, we recorded the hourly feeding activity of parents when the nestlings from their first and second breeding attempts were 7 and 12 days old. Feeding frequency of the first brood increased with the age of the nestlings and also with the brood size when 12 days old. While the feeding activities of the females were similar with respect to the first and second broods, the males were less active and failed to provide any food to their nestlings in 15 cases out of 28 second broods. In spite of this, the fledglings from the second broods were heavier than those in the first. Such a pattern of male behaviour was possible without being a disadvantage to the chicks because the food supply increased during the breeding season and the female could provide food for the young alone. Thus paternal care was particularly important in times of poor food supply, i.e. during the first brood, where the extent of these males' activity in feeding the 7-day-old nestlings was positively correlated with the average mass of the nestlings. Our results support the idea that the male of monogamous, altricial bird species often makes important contributions to raising the young, especially during periods when it is difficult for the female to do so alone. Males show flexibility in their pattern of parental care, and male Treecreepers change their contribution to the first and second broods within the same season.     

A Long-Term Experimental Study Demonstrates the Costs of Begging That Were Not Found over the Short Term

Parent–offspring conflict theory predicts that begging behaviour could escalate continuously over evolutionary time if it is not prevented by costliness of begging displays. Three main potential physiological costs have been proposed: growth, immunological and metabolic costs. However, empirical evidence on this subject remains elusive because published results are often contradictory. In this study, we test for the existence of these three potential physiological costs of begging in house sparrow (Passer domesticus) nestlings by stimulating a group of nestlings to beg for longer and another group for shorter periods than in natural conditions. All nestlings were fed with the same quantity of food. Our study involves a long-term experimental treatment for begging studies (five consecutive days). Long-term studies frequently provide clearer results than short-term studies and, sometimes, relevant information not reported by the latter ones. Our long-term experiment shows (i) a clear effect on the immune response even since the first measurement (6 hours), but it was higher during the second (long-term) than during the first (short-term) test; (ii) evidence of a growth cost of begging in house sparrow nestlings not previously found by other studies; (iii) body condition was affected by our experimental manipulation only after 48 hour; (iv) a metabolic cost of begging never previously shown in any species, and (v) for the first time, it has shown a simultaneous effect of the three potential physiological costs of begging: immunocompetence, growth, and metabolism. This implies first, that a multilevel trade-off can occur between begging and all physiological costs and, second, that a lack of support in a short-term experiment for the existence of a tested cost of begging does not mean absence of that cost, because it can be found in a long-term experiment.     

The dynamics of somatosensory and visual evoked potentials as a correlate of reversible states of altered consciousness]

Somatosensory and visual evoked potentials (EPs) of the brain of 17 sensitive subjects (extrasenses) and 12 ordinary healthy subjects were studied. It was found that during extrasensory activity (direct impact, meditation) in comparison to rest values, the amplitude of intermediate and late components of visual and somatosensory EPs of both hemispheres and early components of somatosensory EPs of ipsilateral in relation to stimulation hemisphere diminished 2-4--fold. There was a recovery of these components after discontinuation of extrasensory activity. It is shown that ordinary subjects could not change their EPs when they tried their best to decrease EPs. It is shown that ordinary subjects could not change their EPs when they tried their best to decrease EPs. It is suggested that the ability of extrasenses for reversible changes of their mind by direct adjustment of the activity of the ascending nonspecific systems of the brain and by alterations of interhemispheric relations forms the basis of extrasensory activity.     

Restoration of the behavioral reactions of Rana esculenta frogs during regeneration of visual nerve fibers]

After sectioning the optic nerve, various forms of visually guided behaviour in the frog R. esculenta recover unevenly. Within 16--20 days, the onset of reactions was observed which are associated with perception of relatively large unmoving objects during active locomotion of animals (1); within 55 days -- avoidance reactions (2); within 90 days -- feeling reactions (3) were formed. In electrophysiological experiments it was shown that axons of the ganglionic retinal cells from various classes form contacts with the tectum also at different periods. The data obtained confirm the significance of specialized "canalization" of the retino--central nervous systems of transmission and evaluation of visual information for organization of separate forms of visually monitored behaviour in frogs.     

Development of the hypothalamic-cortical interrelations in the ontogeny of the cat

Under chloralose narcosis, employing the evoked potentials method, studies have been made on the projection of the posterior hypothalamus to the frontal cortex in 1-30 days old kittens. The animals were divided into 3 age groups: 1-9, 10-19 and 20-30 days. Studies of the EPs in different points of pericruciate zone showed that these potentials are observed in all the investigated points from the first days of postnatal life. The latent period of responses in the youngest animals varied from 40 to 80 ms, exhibiting insignificant fluctuations depending on the cortical zone investigated. From the very beginning of postnatal life, in the same cortical zone the EPs may be observed in response to stimulation of the ischiadic nerve as well. In older animals, the latent period of the EPs decreases in all the points, the decrease being most significant near the crucial fissure. To the 30th day of postnatal life, the EPs in this zone with respect to their latency and configuration became quite similar to those in adult animals. In the third age period, the latency varies from 6 to 10 ms in the focus of maximum activity; with the removal of the recording electrode from this zone the latent period of the hypothalamo-cortical responses increases up to 30-40 ms. Overlapping of the EPs in response to central and peripheral stimulation was observed at all age periods.     

Parental Alarm Calls of the White‐Crowned Sparrow Fail to Stimulate Corticosterone Production in Nest‐Bound Offspring

Alarm calling by parents is widespread among animals and has strong implications for parent and offspring fitness, yet it is virtually unknown whether parental alarm calls can initiate a corticosterone response in offspring. We investigated whether parental alarm calls of the white‐crowned sparrow, Zonotrichia leucophrys, activated the corticosterone response of their nest‐bound young, as such a response might prepare older nestlings for premature fledging and increase their survival when contacted by a predator at the nest. We conducted an experiment in which nestlings were either exposed to parent alarm calls (treatment) or experienced a period without parental alarm calls (control) immediately prior to blood sampling. We then sampled nestlings to measure corticosterone levels within 4 min of first contact (baseline corticosterone) and 60 min later (handling‐induced corticosterone). Young nestlings (i.e. 3–4 d post‐hatch) did not exhibit a corticosterone response to parental alarm calls or to handling, as mean corticosterone levels were similar in the control and treatment groups for both baseline and 60‐min post‐baseline samples. Against our predictions, there was no difference in mean levels of baseline corticosterone between control and treatment groups in older nestlings (i.e. 7?8 d post‐hatch) that were capable of surviving out of the nest. However, we did find a significant increase in mean levels of corticosterone after handling in both groups, which indicated that older nestlings were able to mount a functional corticosterone response when confronted with a potential predator. Why older nestlings did not initiate a corticosterone response after exposure to parental alarm calls is unclear but may have occurred because the costs of mounting such a response outweighed the benefits, perhaps because of growth or developmental costs.     

Effect of Brood Age on Nestling Diet and Prey Composition in a Hedgerow Specialist Bird,the Barred Warbler Sylvia nisoria

The composition and quality of food provided to nestling birds influence their growth and development and offers key insight into the ecological requirements of birds. One bird species whose feeding ecology is poorly understood is the Barred Warbler (Sylvia nisoria), which utilizes semi-natural shrubby vegetation in agroecosystems. Because Barred Warbler nestlings vary greatly in body mass we hypothesised that diet and prey properties (size, diversity, taxonomic composition, and chitin content and resulting body hardness and digestibility) would differ as the nestlings aged. We quantified the diet based on faecal analysis, sampling faecal sacs from the nestlings pooled into three age classes: 2-3 days old, 4-6 d old, and 7-9 d old. Nestlings were provided a wide diversity of food and a strong relationship existed between food characteristics and nestling age. The youngest nestlings (2-3 d old) had the lowest values of each dietary characteristic (diversity, number and total biomass of prey, and individual prey weight), that were significantly lower than the oldest nestlings (7-9 d old). Nestlings aged 4-6 d exhibited intermediate dietary characteristics. Differences in dietary composition of the six major food types showed marked differences between the individual broods and age categories. Percentages of the number and biomass of soft-bodied prey were highest in the diet of 2-3 d and 4-6 d old nestlings, and decreased with increasing age, whereas the opposite trend was observed in the percentage of intermediately and heavily chitinised prey. Parent Barred Warblers probably preferentially select soft-bodied prey for the youngest nestlings, and satisfy the greater energy demands of the older ones by providing them with a greater variety of prey containing more chitin, as well as plant food. The provisioning of less-readily digestible prey to older nestlings suggests that as the quality of food decreases the quantity increases, implying that the youngest nestlings may be physiologically limited as regards their ability to digest more heavily chitinised prey.     

Sudden reversal of phototaxis during the development of nestling birds

Starling, Sturnus vulgaris, nestlings from about 10 days of age moved away from light, i.e. they were negatively phototactic. However, several days before fledging, they changed to move towards light, probably a necessary prerequisite for fledging. The phototactic reversal was correlated with physical development and the ability to fly. In contrast to most studies or newly acquired behaviour, there was no change in response time associated with the reversal. However, hunger reduced the response time of hand-reared nestlings. It is suggested that a positive phototaxis for strong fliers or negative phototaxis for flightless young is an adaptive escape response. The reversal of phototaxis is probably a general feature of avian development.     

The morphogenesis of Wulst neurons in the pied flycatcher under conditions of limited afferent inflow]

Golgi preparations of the pied flycatcher Wulst region (the structure analogous to the mammalian visual cortex) were analyzed using the method of computerized morphometry, to study the influence of visual deprivation on the development of different types of neurons selected previously. Deprivation was accomplished by covering the young's eye with nontransparent caps. The experiments were carried out in 10-day-old nestlings (the onset of patterned vision) and 13-day-old nestlings (functioning patterned vision). In 10-day-old nestlings, the deprivation produced constructive changes in dendritic apparatus of projective stellate cells (among them, the most pronounced was more than three-fold increase in the number of foci of maximal branching) practically not affecting the small stellate-like cells. In 13-day-old nestlings, cells belonging to all selected cell types underwent destructive changes: their quantitative characteristics were decreased as compared to those in control nestlings. A large number of tree-like neurons were revealed in the Wulst in the deprived 10-day-old nestlings while in the control age-matched nestlings they were virtually never found. This phenomenon may be explained by the increased affinity to impregnation evoked by deprivation-induced biochemical changes in the tree-like neurons or to increase in their number. In the latter case, the phenomenon may be considered as compensatory, directed at the establishing of contacts with nonvisual afferents.