Effects of monocular deprivation in the nucleus rotundus of zebra finches: a Nissl and deoxyglucose study

Summary We evaluated in zebra finches the effects of monocular deprivation on morphological and physiological features of the nucleus rotundus, the thalamic relay station of the tectofugal pathway. In a first series of experiments neuron size and total volume were estimated in animals deprived for 20, 40 and at least 100 days and compared to values obtained from normally reared birds. Monocular closure for more than 40 days causes a marked hypertrophy in cells receiving their main input from the open eye, whereas the deprived cells are normal in size. However, with only 20 days of monocular deprivation both deprived and non-deprived rotundal neurons are larger than normal. This indicates that monocular closure has a biphasic effect: firstly, an unselective hypertrophy of deprived and non-deprived neurons, and secondly, a subsequent period of shrinkage of the deprived cells to normal values, while cells driven by the open eye remain hypertrophied. The total volume of the deprived n. rotundus turns out to be smaller in all age groups. In a second series of experiments the activity of the n. rotundus of animals monocularly deprived from birth for 100 days was investigated with the 2-deoxyglucose-method (Sokoloff et al. 1977). With binocular stimulation the activity of the deprived n. rotundus was reduced by about 40%. Depriving adult animals for 100 days does not result in asymmetric labeling of the n. rotundus. We interpretate the 2-DG data as evidence for the existence of a sensitive period for the effects of monocular deprivation. The anatomical data suggest, however, that the effects of monocular deprivation in birds are different from those observed in mammals.     

Complete maternal deprivation affects social, but not spatial, learning in adult rats

The effects of maternal deprivation on learning of social and spatial tasks were investigated in female adult rats. Pups were reared artificially and received "lickinglike" tactile stimulation (AR animals) or were reared with their mothers (MR animals). In adulthood, subjects were tested on paradigms of spatial learning and on paradigms involving learning of social cues. Results showed that maternal deprivation did not affect performance on spatial learning, but it did impair performance on the three social learning tasks. The AR animals made no distinction between a new and a previously presented juvenile conspecific. AR animals also responded less rapidly than MR animals at test for maternal behavior 2 weeks after a postpartum experience with pups. Finally, AR animals did not develop a preference for a food previously eaten by a familiar conspecific whereas MR animals did. This study indicates that animals reared without mother and siblings show no deficits in spatial tasks while showing consistent deficits in learning involving social interactions.     

Does visual deprivation in adult animals affect macromolecular metabolism in visual neurons?

Two-wave-length visible cytospectrophotometry of gallocyanin-stained sections has shown that 30-day-long visual deprivation in adult rats results in an augmentation of RNA content per cell in the neurons of all cell layers in visual cortex. Light stimulation which in normally reared rats brought about an accumulation of RNA in visual cortex neurons gave rise in light-deprived animals to a disappearance of the deprivation-induced increase of neuronal RNA content. In retina ganglion neurons, RNA content per cell was not changed after the visual deprivation as well as after the illumination of the deprived rats although in normal animals this stimulation evoked an increase of RNA content in the retina neurons. The conclusion is made about marked alterations in macromolecular metabolism induced by a long-term hypoactivity in central and peripheral visual neurons of adult animals.     

Influence of taste stimulation during the suckling period on adult taste preference in rats

Effects of taste deprivation and selective taste exposure during the suckling period on adult preference for flavored solutions was examined. Taste deprivation was achieved by rearing rat pups "artificially," in individual cups with intragastric feeding from Postnatal Days 4 through 17 or 18. In the first study the effects of artificial rearing on male Long-Evans rats were examined. In the second study female Wistar rats were exposed to a single tastant, sucrose, which was introduced on a background of taste deprivation. Results of both studies were similar. No differences in taste sensitivity or preference were detected between animals subjected to taste deprivation or selective taste exposure and their normally reared littermates. These results suggest that suckling stimulation is not necessary for normal taste development and that the taste system of the rat is not particularly susceptible to the influence of early experience. Other interpretations of these results are also discussed.     

The development of vision in cats after extended periods of dark-rearing

Summary The time course of development of visual acuity for square wave gratings was measured behaviourally in a number of cats that were reared in total darkness until they were either 4 (5 cats) or 6 (1 cat) months of age. Less extensive measurements were also made on animals reared in a similar manner until they were either 1 1/2 or 10 months old. Initially, all the animals appeared to be blind, but signs of vision became evident after periods of time in an illuminated environment that ranged from a few days, in the case of animals dark-reared for only 1 1/2 to 4 months, to 1 to 2 months for those animals that were deprived for 6 months or more. Thereafter, visual acuity as measured on a jumping stand progressively improved, reaching, in the case of animals deprived for 4 months, values that were comparable to those of normal animals (6.9 cycles/deg) after 4 months of exposure to light. The animal deprived for 6 months remained apparently blind for a month and eventually attained an acuity (5.7 cycles/deg) that was somewhat less than that of normal animals.The fact that such high acuities can be achieved after periods of binocular deprivation that extend throughout the classically defined critical period suggest that the effect of dark-rearing is somehow to impede the natural decline with age in the degree to which cortical neurones are susceptible to environmental modification.     

Visually guided reaching in the cat reared in fixed or random frequency stroboscopic light

The effect of deprivation of visual perception of movement in a visuo-motor task has been tested in cats reared in stroboscopic light since birth. Three cats were reared in light of fixed (2 flash/sec, flash duration 2 msec) and three in light of random (between 0.5 and 3.5 flash/sec) frequency. These 6 animals, together with 6 control cats, underwent (as adults) a test of visual control of reaching for a target with a paw, with operant conditioning. While the cats raised in fixed frequency stroboscopic conditions (FFS) showed no deficit, those raised in random frequency condition (RFS) exhibited significantly less precise guidance than FFS and control animals.     

Proprioceptive signals from extraocular muscles gate experience-dependent modifications of receptive fields in the kitten visual cortex

Summary The California ground squirrel (Spermophilus beecheyi) has two classes of cone photopigments (_max = 440 and 525 nm). Under photopic conditions about 30% of all optic nerve fibers receive inputs from both cone classes, the remainder are driven solely by the 525 nm cone. Recordings were made from optic nerves in young ground squirrels to trace the development of their spectral responsivity. Animals were reared from birth in one of three photic environments: white light, darkness, or red light. In the youngest ground squirrels examined (ca. 50 days old) many units receiving inputs from the 525 nm cone were found, but the proportion of units receiving inputs from both cone classes was significantly lower than that of adults. From these initial low levels the proportion of such units increases gradually. Adult proportions were achieved at varying rates which depended on the photic environment in which the animal was reared: animals reared in white light achieved the adult standard earliest, those reared in darkness somewhat later, and the animals reared in red light required much longer to achieve the adult organization. We conclude that: (a) the neural substrates for normal color vision in this species develop to some extent postnatally, and (b) the normal sequence of development can be significantly extended by spectral environments which provide a highly biased stimulation of the two cone mechanisms.Supported by a grant from the National Eye Institute (EY-00105)     

Recovery of function in cat visual cortex following prolonged deprivation

Summary Evidence that there is a critical period during which response characteristics of neurons in visual cortex of the cat may be influenced has been provided in several studies, which suggest that the period of influence is restricted to the first few months of life. Using a somewhat different experimental procedure, we have obtained evidence that cortical units retain plasticity long after the end of this period has passed. In our procedure prolonged visual deprivation was followed by exposure in a normal visual environment. The animals were maintained throughout the first year of life either in total darkness or in an enclosure illuminated intermittently by a strobe light. Following the period of deprivation, electrophysiologic recordings were taken from some of these animals. The remaining cats were permitted 6–12 months in a normally-illuminated environment prior to recording. Cats of the same age reared from birth in a normally lit environment were also recorded.Cortical neurons in cats deprived of any normal visual experience rarely show orientation selective responses. In animals allowed subsequent normal visual experience about one-half of the units studied exhibited this property. This level of response specificity is intermediate between that of normally-reared and recently-deprived animals. While most cortical units in normally-reared cats exhibit direction selectivity, this property is rarely observed in the recovery cats. A number of unit types which are rarely observed in either normal or totally deprived animals were encountered in cats that had normal exposure following prolonged deprivation. A convergent strabismus was observed, in contrast with the divergent strabismus often shown by cats immediately following prolonged visual deprivation. This shows that ocular alignment as well as cortical unit properties can remain plastic in the adult.Supported by NRC Grant No. A9939 and M.R.C. Grant No. MA5201 (to M.C.) and Grants from NIH and the Sloan Foundation (to A.H.).     

Early separation of young rats from the mother and the development of play fighting

Play fighting was studied in rats which were either normally reared (separated from the mother on day 30) or prematurely separated from the mother on day 15. The animals were tested in pairs on days 33, 36 and 39 of age and play fights were recorded. Play fighting behavior increased markedly after three days of social isolation. In all pairs of normally reared animals (controls, 30S) the rats with the higher pinning scores on the first day also had the higher frequency of pinning on the second and third day of the test. The same trend in the distribution of pinning was found in pairs where the normally weaned animals (30S) played with the early weaned ones (15S). The latter, however, were always pinned by the former (30S) and had significantly lower pinning scores. Such a stable distribution of pinnings did not develop during play fights in pairs of early weaned animals (Group 15S).     

Innate and environmental factors in the development of the kitten's visual cortex.

1. This is a study of the receptive fields of 771 cells recorded in the visual cortex of twenty-five kittens reared normally or subjected to various kinds of visual deprivation or environmental manipulation. 2. Kittens deprived of patterned visual experience, by dark rearing or diffuse occlusion of the eyes, have a majority of cirtical neurones with little or no specificity for the orientation or axis of movement of visual stimuli. However, in such deprived animals, especially those younger than 3 weeks, there are a number of genuinely orientation selective cells. They are broadly "turned" (by adult standards), they are almost always of the simple type, are heavily dominated by one eye, and are found mainly in the deeper layers of the cortex, especially layer IV. 3...     

Regulation of feeding behavior in the prepubertal female rat.

Responses to challenges of long-term regulation of feeding behavior were compared between adult and weanling female rats. Adulteration of a high fat diet with NaCl caused both adult and weanling rats to reduce their food intake, but neither group refused to eat. Food deprivation for 24 hr was followed by an increase in feeding for both adult and weanling animals during a period when food intake is normally very low. Continued limited food access to 2 hr during the light period was compensated for by an increase in the normal food intake for this period for both adult and young female rats. It was observed that both adult and weanling rats showed a marked preference for the more dilute glucose solution when given a choice. In addition, both groups maintained a constant caloric intake during presentation of the glucose solutions by adjusting their intake of a solid food source. In each challenge of long-term regulation of feeding behavior, the response of weanling animals was as good or superior to that shown by adults. It is concluded that weanling female rats regulate their feeding just as adults to maintain long-term energy balance. It was also observed that bilateral lesions placed in the ventromedial hypothalamus (VMH) at 21 days of age resulted in reduced daily food intake and retarded body weight gain. Furthermore, young rats with VMH lesions failed to respond to 24 hr of food deprivation or limited food access. These data suggest an important role for the VMH in the long-term regulation of feeding in young rats.     

Effects of a cold environment on energy-related enzyme activities in the postnatal rat.

Liver glucose-6-phosphatase and lipase-esterase, liver and muscle glycogen phosphorylase, and brown fat lipase-esterase activity changes were studied during the postnatal development of rats born and growing up in temperatures of +5 and 20 degrees C. Liver glucose-6-phosphatase activity was highest at the age of 4 days in both environments. In the age groups 20-67 days glucose-6-phosphatase activity was higher in animals living in a cold environment than in those reared at room temperature. At birth, glycogen phosphorylase activity was high in the liver but very low in the muscle. No difference was found between the two temperatures. The lipase-esterase activity in the liver was very low at birth, rising to adult level by the age of 30 days, while in the brown fat the activity was already high at the time of birth and clearly higher in rats born in a cold environment than in those born at room temperature. At the time of birth the relative and absolute weight of brown fat were also clearly higher in rats born at +5 degrees C than in those born +20 degrees C.     

Electroretinogram changes associated with retinal upregulation of trophic factors: observations following optic nerve section

The purpose of the present work was to assess whether upregulation of trophic factors and protection from damage induced in the retina by optic nerve section are associated with changes in the flash electroretinogram (ERG). We have examined the ERG in adult pigmented rat at different survival times over a period of 3 months following section of the optic nerve. The a-wave was analyzed using the Lamb-Pugh model and the parameters of best fit were estimated in control animals and at successive survival times. The amplitudes of the a- and b-waves were reduced over the first 7 days after nerve section. The a-wave recovered its relative amplitude by 21 days, but the b-wave remained depressed 5 weeks following nerve section. Analysis of the a-wave indicated a 20-30% reduction in the dark current of sectioned eyes at 7 days survival. A significant reduction of the amplification constant was observed in both nerve-sectioned and nerve-intact eyes, relative to normal and sham-operated controls. This reduction persisted to the longest survival time examined. The reduction of the a-wave at 7 days after nerve section coincides with a period of upregulation of ciliary nerve trophic factor. The amplification factor is influenced over a longer time course, which corresponds with a period of up-regulation of basic fibroblast growth factor. These changes in growth factor expression and ERG parameters are in turn associated with protection of photoreceptors against light damage. Present results suggest that the sensitivity of the retina to light may be regulated by mechanisms which protect photoreceptors against stress.     

Behavioral and hormonal responses to stress in the newborn mouse: Effects of maternal deprivation and chlordiazepoxide

These studies investigated behavioral and hormonal responses to stress in developing mice. Experiment 1 examined the effects of 24-hr maternal deprivation on corticosterone (CORT) secretion and ultrasonic vocalization (UVZ) rate in 4-, 8-, and 12-day-old mice. At these ages, exposure to a novel environment resulted in minimal changes in CORT secretion. Maternal deprivation increased pups′ CORT secretion in an age-dependent fashion but did not affect their UVZ rate. The aim of experiment 2 was to test the effects of cholordiazepoxide (CDP), an anxyolytic compound, on CORT secretion and UVZ in both normally reared and in maternally deprived 8-day-old mice. CDP administration elevated CORT increases in deprived (DEP) animals. CDP affected UVZ only in nondcprived (NDEP) animals: UVZ ratewas decreased by high CDP doses Overall, these findings demonstrate that the infant mouse shows a period of stress hyp9oresponsiveness similar to the rat and that maternal presence contributes to inhibit adrenocorticalactivity. CDP administration, butnot novelty exposure, increased CORT secretion in 8-day- old normally reared mice suggesting that during the stress hyporesponsive period, the HPA axis is capable of responding only to specific stimuli. Changes in HPA axis activity and UVZ rateresulting from maternal deprivation and/or CDP challenge do not seem to be directly related. ©1994 John Wiley & Sons, Inc.     

Critical periods in development for susceptibility to the effects of stroboscopic rearing in the rabbit visual cortex

Previous studies have shown that rearing rabbits in a stroboscopically illuminated environment results in a decrease in orientation and direction selectivity and an increase in responsivity to stroboscopic stimuli among neurons in area 17. In the present study, the critical period for susceptibility to these effects was studied by varying the time of onset of the deprivation. Groups of Dutch belted rabbits were reared normally and then placed in a stroboscopically illuminated environment at ages 1, 2 or 3 months, and response characteristics of visual cortical neurons were compared with those obtained from normal rabbits and from rabbits reared in a stroboscopic environment from birth. Results show that the different effects of strobe rearing have different critical periods. Increased responsivity to stroboscopic stimuli was seen only in rabbits deprived from birth. The effects of strobe rearing on both direction and orientation selectivity decreased with increasing age at the time of onset of the deprivation. However, only direction selectivity was modified by deprivation beginning at 3 months of age.     

Environmental influence on development,behavior, and endocrine morphology of gerbils

Gerbils reared under standard laboratory conditions grow and develop more rapidly, achieve sexual maturity when younger, and are less reactive to stimulation than gerbils reared in environments providing access to a tunnel-like shelter. Gerbils reared in open cages have lighter adrenal glands, heavier pituitary glands, and heavier reproductive organs than gerbils raised with access to shelter. Comparison of gerbils reared in cages providing access either to opaque or transparent shelter with animals maintained in open cages either on a 12-hr light-dark cycle or in constant darkness revealed that different aspects of environments providing shelter affected different characteristics. Opportunity to move from an open area to a sheltered one increased behavioral reactivity. Reduced exposure to illumination affected developmental rates, reproductive organ and pituitary gland weights. Both reduced exposure to illumination and access to a shelter affected adrenal gland and body weights. These data suggest that expression of the phenotype typical of domesticated gerbils requires deprivation of a variety of stimuli normally experienced by burrow-dwellers during ontogeny.     

Maternal effects in infant and adult phenotypes of 5HT1A and 5HT1B receptor knockout mice

The influence of the pre- and postweaning maternal environment on the offspring's phenotype was examined in 5-HT1A and 5-HT1B receptor knockout mice (KO1A and KO1B, respectively). We have previously shown that, when born to and raised by homozygous dams of the same genotype, adult KO1A are more anxious than wild-type (WT) mice, and adult KO1B are hyperactive and slightly less anxious than WT mice. We extend our studies here to the behavioral results of the offspring's own genotype, when the dam's genotype is constant, and the effects of the dam's genotype when the offspring's genotype is constant. In Experiments 1 and 2, KO1A-/- pups produced less ultrasonic vocalizations (USV) than controls in an isolation test on postnatal Day 7 when born to and reared by KO1A dams, either -/- or +/-. Heterozygous F1 pups reared by KO1A-/- dams produced more USV and were less anxious in the plus-maze at 2 to 3 months of age than F1 pups born to and reared by WT dams (Experiment 3). F1 pups reared by KO1B-/- dams produced less USV and were more anxious in the plus-maze than F1 pups reared by WT dams (Experiment 4). The results support a role for maternal effects that may comprise direct effects such as the dam's behavior and nutritional care of the pup, and possibly more complex indirect effects through the establishment of idiosyncratic dam-pup dyadic interactions. We recommend that breeding techniques that rely on same genotype (mutant-mutant or WT-WT) breeding pairs not be used to generate offspring when the focus of research is the study of gene function, but rather when familial effects need to be studied.     

Birth of normal mice after removal of the supernumerary male pronucleus from polyspermic zygotes

Each year, world wide, tens of thousands of zygotes derivedfrom the in-vitro insemination of human oocytes undergo polyspermicfertilization. These embryos must presently be discarded becauseit has never been demonstrated in any mammal that polyspermiczygotes can develop normally to term after removal of the supernumerarymale pronucleus. Our study was undertaken to test the developmentalpotential of polyspermic zygotes corrected by micromanipulation.Mouse oocytes were inseminated zona-free, and poly-spermic zygoteswere manipulated so as to remove one of the two male pronuclei.Surviving embryos were then observed for further developmentin vitro and after transfer into pseudopregnant females. Of58 zygotes manipulated, 18 developed to the blastocyst stageand were transferred. Five animals (two male and three females)were born. The agouti coat colour marker confirmed the genotypesof the gametes. All five animals developed to normal-appearingadults, and all five produced at least 10 normal offspring.One adult founder animal was karyotyped and found to have anormal chromosome complement These results demonstrate for thefirst time that a mammalian egg that has undergone polyspermicfertilization can develop normally after restoration of thediploid state by micro-manipulation. Accordingly, the resultsprovide impetus for attempting to rescue polyspermic human embryos.     

Delayed response to light stimuli in binocularly deprived cats

Cats binocularly deprived of pattern vision, born and cagereared in the laboratory, were trained on the delayed response task involving light stimuli with 0-, 5-, and 15-s delay. Control cage-reared animals, also laboratory born were not deprived visually. No significant group difference was found in the delayed response learning, both groups performing poorly, as compared to the earlier data reported on cats reared without environmental restriction. The groups differ, however, in reaction time (RT), as in the visually deprived animals a lower proportion of responses with shorter RT was observed than in the controls. Conversely, for responses to the actual light stimuli a higher proportion of shorter RT was found in the deprived animals than in the controls.     

Visual cortical cells: their developmental properties in normal and dark reared kittens.

582 units were recorded in area 17 in twenty-one normally reared kittens, and fourteen dark reared ones, aged between 8 and 42 days. 2. Four classes of neurones were defined: (a) non-activable cells that cannot be excited by any peripheral stimulation; (b) non-specific cells that are sensitive to a visual stimulus moving in any direction; (c) immature cells that are preferentially excited by a rectilinear stimulus but are unselective for its precise orientation; (d) specific cells that appear to be as selective for orientation as the simple or complex cells of the adult cat. 3. 23% of the cells presenting adult characteristics of specificity in terms of directionality and orientation are present in both the normally reared and in the dark reared kittens as soon as the first visual response (12 days) appears. 4. In normally reared kittens the proportion of specific cells increases with age, while that of the non-specific cells decreases. 5. Up to 3 weeks of age there is no significant difference in the proportion of the different types of cells in the dark reared from the normal kittens. But thereafter in the dark reared kittens the specific cells tend to disappear while the non-specific cells increase in number. 6. This confirms the view that cells with some highly specific response properties of the adult visual cortical neurones, especially in relation to orientation specificity, are present in the earliest stages in the absence of all visual experience. However, visual experience is necessary to maintain and develop these specific cells after the third week of post-natal life.