[EEG in altricial pied flycatcher nestlings during the functional sates related with natural behavior cycle].

Electrical brain activity accompanying various forms of behavior was studied in 11-day-old pied flycatcher nestlings. Wavelet analysis of EEG, recorded from symmetrical areas of caudomedial nidopallium (higher avian auditory center) during rest, passive and active wakefulness and movements showed that the major rhythmical EEG component was confined to low-frequency range in all four states. The significant difference from other states was observed only during movements: spectral power in the range of 1-3 Hz decreased while that in the range of 5-20 Hz--increased. The range of 3-5 Hz revealed, in all functional states, the interhemispheric asymmetry of spectral power that could be due to asymmetrical embryonic development of avian visual projections. Active wakefulness and movements were characterized by high positive correlations between spectral power in right and left hemispheres. During rest this correlation was negative. The correlation values during passive wakefulness and rest were rather low that could indicate disintegration of neural connections.

[Visual input affects the expression of the early genes c-Fos and ZENK in auditory telencephalic centers of pied flycatcher nestlings during the acoustically-guided freezing].

The present study analyzed expression of transcriptional factors c-Fos and ZENK in 9-day-old pied flycatcher nestlings' (Ficedula hypoleuca) telencephalic auditory centers (field L, caudomedial nidopallium and caudomedial mesopallium) involved in the acoustically-guided defense behavior. Species-typical alarm call was presented to the young in three groups: 1--intact group (sighted control), 2--nestlings visually deprived just before the experiment for a short time (unsighted control) 3--nestlings visually deprived right after hatching (experimental deprivation). Induction of c-Fos as well as ZENK in nestlings from the experimental deprivation group was decreased in both hemispheres as compared with intact group. In the group of unsighted control, only the decrease of c-Fos induction was observed exclusively in the right hemisphere. These findings suggest that limitation of visual input changes the population of neurons involved into the acoustically-guided behavior, the effect being dependant from the duration of deprivation.

[Activation of tectofugal visual system of the pied flycatcher nestlings at early developmental stages of feeding behavior guided by diffuse photosensitivity].

Immunohistochemical detection of c-Fos in serial frontal sections of the brain of Pied flycatcher nestlings was used to map the sensory structures involved in early forms of feeding behavior. The c-Fos content was quantitatively analyzed in the higher structures of thalamofugal (Wulst area) and tectofugal (entopallium) visual pathways during visually-guided feeding behavior in 6-day-old nestlings at the stage of diffuse photosensitivity. Induction of c-Fos was not observed in the Wulst area which is known to be involved in the feeding integration in adult bifoveal birds. Induction of c-Fos was detected in the ventral area of entopallium containing neurons that are, according to literature, sensitive to a luminosity change. In the entopallium of 6-day-old nestlings, asymmetry in the evoked c-Fos expression was observed, probably reflecting the asymmetry of the visual projections originating in the embryonic period.

[Visual deprivation affects the development of auditory sensitivity during the period of maturation of freezing response in pied flycatcher nestlings].

Recording of evoked potentials (EP) from the higher auditory center of birds field L of the nidopallium was used to study the development of the auditory sensitivity in normally developing vs visually deprived pied flycatcher nestlings aged 6-9 days. The visual deprivation was shown to induce a significant decrease in the absolute auditory EP thresholds in the frequency range of species-typical food call (1-3 kHz) during the period corresponding to the time of the vision involvement into the feeding behavior in the normal young (6 days post-hatching). In the frequency range of species-typical alarm call (4-5 kHz), EP thresholds in visually deprived nestlings were significantly lower than in the control birds during the period corresponding to the time of the vision involvement into the defense behavior of the latter (8-9 days post-hatching). With account made for the previous data demonstrating the decrease of efficiency of acoustic signals provoking freezing in visually-deprived nestlings, it is reasonable to suggest that defense behavior develops not just as a response to alarm call or imitating tone pips, but as a whole system, whose norma maturation and functioning requires integration of numerous factors visual afferentation being one of them.

[Prenatal acoustic stimulation and feeding behavior of Japanese quail chicks (Coturnix coturnix japonica)].

Effects of a prenatal rhythmic tone on behavior of Japanese quail chicks were studied on the next days after hatching. The acoustically stimulated chicks demonstrated a significantly more frequent following response, feeding reaction and comfortable behavior when hearing the tone as compared with their controls. Bandwidths stimulating this or another behavior were determined.

[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.

Development of auditory sensitivity of altricial birds: absolute thresholds of the generation of evoked potentials.

The thresholds of the generation of EP in the L field of two to nine day old pied flycatcher nestlings in response to monotonal bursts of varied frequency were investigated. The entire range of auditory sensitivity was divided into three channels on the basis of the character of the age-related dynamics of the thresholds (two to nine days of life): low-frequency (0.3-1.6 kHz), middle- (1.5-4.0 kHz), and high-frequency (5.0-8.0 kHz). Widening of the auditory range in the direction of high frequencies on the 4th to 5th days of nest life was demonstrated. It was shown that the development of auditory sensitivity continues in all three channels in the post-embryonic period (two to nine days after hatching), and that each of these is characterized by its own thresholds time course.

[The development of hearing sensitivity in altricial birds: the absolute thresholds of the generation of evoked potentials]. / Razvitie slukhovoi chuvstvitel'nosti nezrelorozhdaiushchikhsia ptits: absoliutnye porogi generatsii vyzvannykh potentsialov.

Thresholds of field L auditory evoked potentials EP were studied in 1.5-9-day-old nestlings of pied flycatcher in response to pure tone signals of different frequencies. According to the tendencies of age dynamics of auditory EP thresholds (2-9 days of life) all hearing range was divided into three separate channels: low-frequency (0.3-1.0 kHz), intermediate-(1.5-4.0 kHz) and high-frequency (5.0-8.0 kHz) ones. The widening of the hearing range in its high-frequency part was demonstrated on days 4-5 of life. The development of auditory sensitivity was shown to continue within all three channels in postembryonic period (days 2-9 post-hatching), each of the channels being characterized by its own age dynamics of auditory EP thresholds. Reproduction of tape-recorded species song during days 1-3 post-hatching resulted in significant decrease of auditory EP thresholds.

[The effect of acute alcohol administration on auditory evoked potentials in altricial nestlings during the development of natural behavior]. / Vliianie ostrogo vvedeniia alkogolia na slukhovye vyzvannye potentsialy u nezrelorozhdaiushchikhsia ptentsov v period formirovaniia estestvennogo povedeniia.

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.

[Visual evoked potentials of fledglings to ecologically significant stimuli]. / Zritel'nye vyzvannye potentsialy ptentsov na ékologicheski znachimye stimuly.

A study was made of the structure of evoked potentials in the Wulst of the dorsal hyperstriatum in five- to eight-day old nestlings in response to ecologically determined visual stimuli significant for the alimentary behaviour, within the range of their intensity natural fluctuation. It was established that the parameters of the visual evoked potentials correlate with the rate of behaviour manifestation, which depends on the level of alimentary motivation. At a low motivation level (and under Nembutal anaesthesia), latencies of all response components depend on the energetic parameters of the stimuli and to a maximum degree so -- the primary component latencies. At a high level of alimentary motivation, dependence of the response components latencies on the stimuli parameters is pronounced to a much lesser degree, and still less for the primary component. It is assumed that when the subsequent behavioral response is present, evoked potentials are more linked to the processes of organization and realization of behaviour than to the parameters of affective stimulation.

[Increasing selectivity of defense behavior during development of pied flycatcher nestlings]. / Rost selektivnosti oboronitel'nogo povedeniia v ontogeneze ptentsov mukholovki-pestrushki.

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.

[Callosal neurons: monosynaptic connection between them and their descending projections]. / Kallozal'nye neirony: monosinapticheskaia sviaz' mezhdu nimi i ikh niskhodiashchie proektsii.

Antidromic and monosynaptic unit responses to the stimulation of the corpus callosum and the symmetrical cortical area as well as antidromic responses to pyramidal tract and thalamic nuclei stimulation were recorded in the sensorimotor cortex of unanaesthetized rabbits. Out of 182 callosal neurones 13 exhibited transcallosal monosynaptic responses. 8 out of 56 callosal units responded antidromically to pyramidal tract or thalamic stimulation. Thus callosal neurones may be monosynaptically excited by callosal units via the corpus callosum and by the pyramidal tract units. It was also found that a pyramidal tract neurone may send a collateral through the corpus callosum and at the same time have a transcallosal monosynaptic input. The role of monosynaptic transcallosal excitation of callosal neurones is discussed.

[Visual afferentation deficit during diffuse photosensitivity period in nestlings affects morphogenesis in Wulst neurons]. / Defitsit zritel'noi afferentatsii v period diffuznoi fotochuvstvitel'nosti ptentsov vliiaet na morfogenez neironov Wulst.

Golgi-stained preparations were processed with computerized morphometry to study the effect of the deprivation (eyes covered with nontransparent caps) on the development of neurons in the Wulst (the structure analogous to mammalian visual cortex) of pied flycatcher nestlings. Six-day-old nestlings that have only one form of the visual perception--diffuse photosensitivity--were studied. In the previous paper [Korneeva et al., 1994] in was shown that the Wulst of 6-day-old nestlings consisted of non-differentiated neurons and stellate-like cells at different stages of maturation; the latter group was subdivided into more- and less-mature cells. This work proved that even a 1.5-day-long deprivation (actual duration being counted off from the moment of appearance of the first retinal photoreceptors at the age of 4.5 days) resulted in significant changes in the geometry of stellate-like neurons. The changes in less-mature cells were predominantly destructive (decline of all quantitative indices of a cell, including the significant decrease in the total length of dendrites, maximal radius of the dendritic field and cell branching index), while the changes in more-mature cells were constructive (increase in all quantitative cell indices, including statistically significant increase in the soma section area, total length of dendrites, maximal radius of dendritic field and the number of foci of maximal branching). Different reactions of these cell types to the limitation of visual afferentation may be connected with differences in the afferent inflow to less- and more-mature cells or/and with different maturational stages of these neurons at the onset of deprivation.

[Sensory information--an important factor in ontogeny]. / Sensornaia informatsiia--vazhnyi faktor ontogeneza.

Ontogenetic process reveals a row of consecutive stages characterized by the gradual increase in complexity and by the changing specificity of sensory mechanisms basic for the adaptive behavior of the young. The study examines the mechanisms of interaction among different sensory systems during the formation of early behavioral patterns and analyzes why, at a certain stage of development, a particular sensory stimulus loses its efficacy in the organization of a given behavior and is substituted by another one, previously ineffective. A special attention is paid to formation of behavior based on sensory information within the limits of ontogenetically fixed developmental critical periods and to the role of the early sensory experience in learning in adult animals.

Effects of visual deprivation on the development of auditory sensitivity during formation of the freezing reaction in pied flycatcher nestlings.

Recording of evoked potentials from the higher center of the auditory system - field L of the nidopallidum - was used to study the formation of auditory sensitivity in normally developing and visually deprived pied flycatcher nestlings aged 6-9 days. Restriction of visual afferentation was found to produce significant reductions in the absolute threshold of auditory evoked potentials in the frequency range of the species-specific food call (1-3 kHz) during the period at which vision acquires a role in providing sensory support for feeding behavior in control nestlings (six days). In the frequency range of the species-specific alarm call (4-5 kHz), the thresholds of auditory evoked potentials were significantly lower than those in controls during the period at which vision acquires a role in providing sensory support for defensive behavior (8-9 days). Taking account of previous data showing decreases in the efficiency of acoustic signals in evoking freezing reactions in visually deprived nestlings, it is suggested that defensive behavior develops not simply as a response to the acoustic alarm call or tones imitating it, but as a system whose complete formation and functioning require integration of a series of factors, including visual afferentation.