TfM mutation and masculinization versus feminization of the mouse central nervous system.
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Aggression↗
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Results for “IMPRINTING (PSYCHOLOGY)”
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Evidence that random and imprinted Xist expression is controlled by preemptive methylation.
The mouse Xist gene is expressed exclusively from the inactive X chromosome and may control the initiation of X inactivation. We show that in somatic tissues the 5' end of the silent Xist allele on the active X chromosome is fully methylated, while the expressed allele on the inactive X is completely unmethylated. In tissues that undergo imprinted paternal Xist expression and imprinted X inactivation, the paternal Xist allele is unmethylated, and the silent maternal allele is fully methylated. In the male germline, a developmentally regulated demethylation of Xist occurs at the onset of meiosis and is retained in mature spermatozoa. This may be the cause of imprinted expression of the paternal Xist allele. A role for methylation in the control of Xist expression is further supported by the finding that in differentiating embryonic stem cells during the initiation of X inactivation, differential methylation of Xist alleles precedes the onset of Xist expression.
Animals↗
Changes in telencephalic catecholamine levels in the domestic chick. Effects of age and visual experience.
The concentrations of adrenaline, dopamine and noradrenaline were measured in 3 regions of the domestic chick telencephalon: (a) the Wulst; (b) a medial forebrain sample comprising mainly the intermediate part of the medial hyperstriatum ventrale (IMHV); and (c) a basal forebrain sample comprising mainly paleostriatum augmentatum. There was no significant left/right hemispheric asymmetry in the concentration of any of these catecholamines in any region studied. Adrenaline was undetectable in the Wulst and medial forebrain samples and only trace amounts were found in the basal forebrain samples of 1-day-old, light-reared chicks. Dopamine concentrations of 9.13 +/- 1.13 (S.E.M.) ng/g were present in the Wulst, 16.66 +/- 2.56 ng/g in the medial forebrain and 121.19 +/- 33.06 ng/g in the basal forebrain samples at hatching. These levels did not alter with age or with visual experience of an imprinting stimulus during the first 50 h post-hatch. At hatching, noradrenaline concentrations of 35.83 +/- 8.61 ng/g were present in the Wulst, 26.09 +/- 3.75 ng/g in the medial forebrain and 53.13 +/- 7.85 in the basal forebrain samples. The noradrenaline concentrations in the Wulst and medial forebrain samples increased significantly over the first 50 h post-hatch in dark-reared chicks. Visual experience increased noradrenaline levels in all 3 regions of the telencephalon studied.
Aging↗
A light and electron microscopic study of the development of two regions of the chick forebrain.
The post hatch development of two regions of the chick telencephalon has been studied using light and electron microscopic quantitative methods. The hyperstriatum ventrale is a region known to be involved in the learning process of imprinting, and hyperstriatum accessorium is a primary telencephalic visual projection area. There were significant changes in synaptic density, neuronal density, glial cell density and in the synapse/neuron ratio in hyperstriatum ventrale. In contrast, hyperstriatum accessorium showed a greater degree of stability. The most rapid changes were seen in the immediate post-hatch period. This coincides with the period during which the critical period for imprinting lies.
Animals↗
Acoustic imprinting in guinea fowl chicks: age dependence of 2-deoxyglucose uptake in relevant forebrain areas.
In 7-day-old guinea chicks play back of an imprinted acoustic stimulus was previously found to correlate with increased uptake of 2-deoxyglucose (2DG) in 3 rostral forebrain areas (HAD, LNH and MNH). Subdivisions of these areas defined by 2DG labelling may be association fields. Auditory areas did not show labelling differences between imprinted and control animals. In the present study imprinted guinea chicks of different age and with different experience were used in the 2DG experiments. Seven-day-old chicks (beyond the sensitive phase), 4-day-old (at the decline of sensitive phase) and 1- and 3-day-old chicks (within the sensitive phase) were given a 2DG injection and afterwards heard the stimulus to which they had been imprinted previously (1.8 kHz, 3 tone pips per s). While the typical labelling pattern was weak or absent in 1-4-day-old chicks the older animals consistently had high 2DG uptake in these areas. Unsuccessfully imprinted 7-day-old chicks, having all the behavioral test experience, showed no or weak labelling. These results are related to current literature on reticular activation of the relevant areas and on morphological changes there with termination of the sensitive phase. It is argued that the reticular activation of these areas, e.g. attention mechanisms are instrumental in securing imprinting success and that subsequent reorganization of the areas leads to stronger metabolic activation after the sensitive phase.
Acoustic Stimulation↗
Auditory imprinting leads to differential 2-deoxyglucose uptake and dendritic spine loss in the chick rostral forebrain.
Newly hatched chicks of the domestic fowl (White Leghorn) were imprinted to an acoustic stimulus (Group I: 400 Hz, 3 bursts per s, Group II: 900 Hz, 2 bursts per s) and tested in a straight runway with loudspeakers behind two opposite goal boxes. Those chicks were considered imprinted which headed for the imprinting stimulus in an approach test and subsequently preferred it to a new stimulus (imprinting stimulus of the other group) in a simultaneous discrimination test. On day 7 after hatching (after the sensitive phase) imprinted chicks and naive controls were injected with 2-[14C]deoxyglucose (2DG) and exposed to the imprinting stimulus. Autoradiographic analysis of their brains revealed 3 well demarcated areas of increased 2DG accumulation in the rostral forebrain of imprinted chicks compared to controls: HAD in the rostral Wulst; MNH, an auditory area in the rostromedial neostriatum and hyperstriatum ventrale; LNH in the rostrolateral neostriatum and hyperstriatum ventrale. Analysis of these brain areas in 7-day-old acoustically imprinted and control animals with the Golgi-Cox method revealed a highly significant reduction of spine frequency of a large neostriatal neuron type in MNH of imprinted chicks. An additional Golgi-Cox analysis was carried out with chicks imprinted on a broody hen, i.e. on the whole spectrum of natural stimuli. In that group spine frequency of the same neuron type was between that of acoustically imprinted and control animals. A hypothesis of filial imprinting is presented which considers spine loss as a crucial mechanism.
Acoustic Stimulation↗
Are specific proteins implicated in the learning process of imprinting?
Day-old chicks were exposed for 0.5 h to overhead lighting ('primed') and then imprinted by exposing them for 90 min to a rotating red box. The chicks were otherwise maintained in darkness. Immediately after training these chicks (n = 16), together with 16 primed and 16 dark-reared controls were killed. Samples from the left cerebral hemisphere were removed including (i) the intermediate and medial part of the hyperstriatum ventrale (IMHV), a region which is crucial for imprinting, (ii) the posterior neostriatum and (iii) the visual Wulst. The samples were incubated with [35S]methionine, processed for SDS slab gel electrophoresis and autoradiographs prepared. The optical densities of various bands were measured 'blind'. For no band was there a significant interaction (ANOVA) between brain region and experience. Optical density was correlated with approach activity during training, a measure of behaviour which correlates with the amount chicks learn. Only for IMHV were correlations significant: a negative correlation (P less than 0.01) for approximately 50 kDa band and positive correlation (P less than 0.001) for an approximately 80 kDa band. These results suggest that associated with training there is a reduction and an increase in the synthesis of proteins in IMHV.
Animals↗
Slice cultures of the imprinting-relevant forebrain area MNH of the domestic chick: quantitative characterization of neuronal morphology.
The persistence of morphological features of neurons in slice cultures of the imprinting-relevant forebrain area MNH (mediorostral neostriatum and hyperstriatum ventrale) of the domestic chick was analysed at 7, 14, 21 and 28 days in vitro. After having been explanted and kept in culture the neurons in vitro have larger soma areas, longer and more extensively branched dendritic trees and lower spine frequencies compared to the neurons in vivo. During the analyzed culturing period, the parameters soma area, total and mean dendritic length, number of dendrites, number of dendritic nodes per dendrite and per neuron as well as the spine densities in different dendritic segments showed no significant differences between early and late periods. Highly correlated in every age group were the total dendritic length and the number of dendritic nodes per neuron, indicating regular ramification during dendritic growth. Since these morphological parameters remain stable during the first 4 weeks in vitro, this culture system may provide a suitable model to investigate experimentally induced morphological changes.
Animals↗
Long-term consequences of exposure to an imprinting stimulus on 'spontaneous' impulse activity in the chick brain.
Young chicks were exposed in a running wheel to an imprinting object, a rotating flashing red box (n = 36 chicks) or a rotating stuffed jungle fowl (n = 18). The net number of revolutions of the wheel toward the imprinting object provided a measure of approach activity during training. The chicks were subsequently anaesthetized and the 'spontaneous' firing rates of units were recorded simultaneously in two regions of the left forebrain hemisphere. One microelectrode penetration was made through a region, the intermediate and medial part of the hyperstriatum ventrale (IMHV) known to be critical for imprinting; simultaneously another microelectrode penetration was made through the visual Wulst. The electrodes were advanced in steps of 250 micron and the spontaneous discharge of multiple units at each site recorded. The mean firing rate from greater than or equal to 3 sites was calculated for IMHV and for the hyperstriatum accessorium of the Wulst. There was a negative correlation between mean firing rate of units in IMHV and approach activity for chicks trained on the box. The effect was: stimulus specific since it was not found in chicks trained on the jungle fowl; and regionally specific since approach activity, depending on conditions which are described, was either not correlated or positively correlated with mean firing rate for neurons in the hyperstriatum accessorium. The positive correlation was not dependent on the training stimulus but on the presence of a visually responsive lamina deep to the hyperstriatum accessorium.
Action Potentials↗
The role of a restricted region of the chick forebrain in the recognition of individual conspecifics.
It has been proposed that there are two neural systems underlying filial preference behaviour in the domestic chick. Firstly, a predisposition which serves to orient the chick towards objects resembling adult fowl, and secondly a learning system which is engaged by particular objects, including the bird's own mother. Lesions to a particular region of the chick forebrain, the intermediate and medial part of the hyperstriatum ventrale (IMHV), impairs the learning system but not the predisposition. The present experiment was designed to test the hypothesis that the IMHV is involved in learning to recognise individual members of a species. Between 6 and 10 h after chicks had hatched, bilateral lesions were placed in the IMHV (n = 16), and the Wulst (n = 16). There were 52 sham-operated controls. Following recovery from surgery (20-28 h later), all chicks were exposed to one of two stuffed jungle fowl for 4 X 50 min. Two hours after the final training session all birds were given a preference test. This test involved the simultaneous presentation of the fowl to which the chicks had previously been exposed and the fowl which they had not previously seen. While both the sham-operated and the Wulst-lesioned groups had a significant mean preference for the fowl to which they had been exposed during training, the IMHV-lesioned birds had no preference. This result is consistent with the hypothesis that IMHV is involved in learning to recognise individual birds, as well as other conspicuous objects.
Animals↗
Glutamate and imprinting memory: the role of glutamate receptors in the encoding of imprinting memory.
Glutamate-sensitive receptors have been implicated in many forms of neural plasticity and learning, including imprinting of chicks. Previous studies have indicated that glutamate binding levels in the left intermediate medial hyperstriatum ventrale (IMHV) region of the chick forebrain increase as a correlate of the acquisition of an imprinting memory; however, it has not been determined whether this is due to an increase in the number of glutamate receptors or to increased receptor affinity. The area specificity of these changes, within the left and right hemisphere, was also unexplored. We have performed Scatchard displacement binding analyses to examine changes in both the number and affinity of glutamate receptors in the left and right hyperstriatum ventrale (HV) and also the left and right archistriatal/lobus parolfactorius (AS/LPO) areas from imprinted and non-imprinted chicks. The results of this study demonstrate lateralised increases in both the number and affinity of glutamate receptors in the left HV area at 7-8 h after imprinting. Significant increases in the affinity, but not the number, of glutamate receptors were found in the left AS/LPO. This suggests that the left AS/LPO, which has previously been shown to be involved in the acquisition of a passive avoidance memory, may also be involved in the formation of an imprinting memory.
Animals↗
Phase specific morphological changes induced by social experience in two forebrain areas of the zebra finch.
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.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Molecular cloning of the kainate-binding protein and calmodulin genes which are induced by an imprinting stimulus in ducklings.
For the formation of imprinting in birds, protein synthesis is known to be essential in the medial hyperstriatum ventrale (MHV) of the forebrain after presentation of an imprinting stimulus. We have searched for the genes whose expressions are increased in duckling's MHV during formation of imprinting, and identified kainate-binding protein and calmodulin genes. This may reflect the formation of glutamatergic pathways in MHV.
Amino Acid Sequence↗
MARCKS and protein F1/GAP-43 mRNA in chick brain: effects of imprinting.
The phosphorylation of MARCKS, but not protein F1/GAP-43, is increased in the intermediate and medial portion of the hyperstriatum ventrale (IMHV) after chick imprinting. Here we investigated if MARCKS, but not F1/GAP-43, gene expression would also be altered after imprinting. We first investigated the constitutive mRNA distribution of MARCKS and F1/GAP-43 in chick brain. MARCKS mRNA was expressed in most cells and exhibited a relatively homogeneous distribution. In contrast, F1/GAP-43 mRNA levels were elevated in discrete brain regions, as we had observed in mammals. The highest F1/GAP-43 mRNA levels in the chick brain were in sensory and associational structures such as the hyperstriatal complex and neostriatum, and lower levels were in structures involved in motor control, such as paleostriatum. These results in chick are consistent with the previously drawn generalization that F1/GAP-43 mRNA is expressed in those brain regions which exhibit synaptic plasticity. After imprinting, MARCKS mRNA levels in IMHV were higher in good learners than poor learners. In contrast, analysis of F1/GAP-43 mRNA levels revealed no differences related to training in any brain region sampled. These selective results for MARCKS but not F1/GAP-43 parallel the prior findings on their phosphorylation, and are consistent with our hypothesis that the very same proteins that are post-translationally modified in association with learning and memory also undergo alterations in their gene expression.
Analysis of Variance↗
Evidence that physiologic levels of circulating estrogens and neonatal sex-imprinting modify postpubertal hepatic microsomal 3-hydroxy-3-methylglutaryl coenzyme A reductase activity.
Intact, but sham-operated female rats had 2- to 3-fold higher levels of hepatic 3-hydroxy-3-methylglutaryl CoA reductase activity than their male counterparts (15--21.5 vs. 6.7--8.7 nmol mevalonate/mg protein per h). The activity of the hepatic enzyme declined to about the same relative degree (40--60%) in male and female rats that were gonadectomized after puberty (53 days of age) and killed 5 weeks later. Implantation of silastic capsules containing 17 beta-estradiol increased the level of hepatic 3-hydroxy-3-methylglutaryl CoA reductase to levels found in sham-operated controls. In rats that were gonadectomized in infancy (12 h old) and killed 7--8 weeks later, the level of enzyme activity was not altered in females, but it was increased from 60--240% in males. Consequently, following neonatal gonadectomy, male-female differences in enzyme activity were no longer apparent. Implantation of silastic capsules containing estradiol in neonatally gonadectomized rats resulted in a doubling of enzyme activity in both males and females. Ovariectomy reduced plasma estrogen levels, but implantation of estradiol in gonadectomized males and females increased the hormone level to that found in sham-operated females. Thus, the results strongly suggest a role for physiologic levels of estrogen as a positive effector of 3-hydroxy-3-methylglutaryl CoA reductase activity. Neonatal sex imprinting also appears to modulate the enzyme activity since sex-mediated differences are effaced by gonadectomy in infancy, but not by gonadectomy following puberty.
Animals↗
Synaptic potentiation and depression in slices of mediorostral neostriatum-hyperstriatum complex, an auditory imprinting-relevant area in chick forebrain.
Long-term potentiation, a tetanic stimulation-evoked, persistent increase in synaptic efficiency, is the most extensively studied form of synaptic plasticity. Intracellular correlates of long-term potentiation have been analysed in mammalian hippocampus and cortex, but not in bird cortical analogues. We present here studies on long-term potentiation in slices of the chick forebrain area mediorostral neostriatum-hyperstriatum complex which receives thalamic afferents and is relevant for auditory filial imprinting. Following afferent tetanic stimulation, population spike potentiation was extracellularly recorded in 25% of the tested neurons for longer than 40 min. Using intracellular recordings, the membrane potential, the amplitude of excitatory postsynaptic potentials, the latency between the test stimulus and the evoked action potentials, and the cellular excitability (excitatory postsynaptic potential-spike relationship) were found to change after the tetanus. A long-term depression following the tetanus was also seen in some units in this area. Furthermore, the mechanisms underlying long-term potentiation were investigated. A large depolarization of resting membrane potential (approx. 36 mV) was characteristic after the tetanic stimulation. N-methyl-D-aspartate receptor channels are necessary for induction of this depolarization, as well as for long-term potentiation, as demonstrated by the effect of DL-2-amino-5-phosphonovaleric acid. After intracellular recordings, the cells were injected with Lucifer Yellow. The combination of electrophysiological characterization and morphological identification suggested that the potentiation came chiefly from type I neurons, which have the largest soma among the neuron types in this area and up to eight dendrites. The results demonstrate that the recognized major phenomena of long-term potentiation are found in an auditory imprinting-relevant area of the chick forebrain, and that this potentiation is dependent on N-methyl-D-aspartate receptor channels. It is noteworthy that behavioural imprinting was previously shown to induce a reduction of up to 47% of the spine frequency of type I neurons and a growth of the remaining spine synapses, all resembling a synaptic selection process. Therefore, the intriguing possibility emerges that mechanisms underlying long-term potentiation are instrumental for this selection process, which involves regressive and proliferative morphological changes.
Acoustic Stimulation↗
Imprinting behavior: influence of vasopressin and ACTH analogues.
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Adrenocorticotropic Hormone↗
Enhancement of performance by methyl beta-carboline-3-carboxylate, in learning and memory tasks.
Benzodiazepines are known to induce a profound anterograde amnesia in man. In this report, it is shown that methyl beta-carboline-3-carboxylate (beta-CCM), an inverse agonist of the benzodiazepine receptor, has the opposite effect; it enhances performance in learning and memory tasks. Three different learning models were used: habituation to a new environment and passive avoidance in mice and imprinting in chicks. The opposite effects of both beta-CCM and the benzodiazepine diazepam were blocked by administration of the benzodiazepine receptor antagonist Ro 15-1788, providing evidence that the benzodiazepine receptor is involved in these effects.
Animals↗