Role of auditory feedback in canary song development.

Describes studies conducted with an inbred strain of Belgian "Wasserschlager" canaries bred selectively by aviculturalists in Europe for particular patterns of singing behavior. As in other songbirds, early deafening had drastic effects on the song of the roller canary, a caudueline finch, resulting in a song that was much simpler and more variable than the normal. The repertoire of syllable types was reduced from 30 to a mean of 5.0. Loud white noise was successfully used as a reversible method of cutting off auditory feedback from vocal behavior. Although suffering permanent elevation of hearing thresholds, Ss reared in noise to 200 days, singing at first like deaf Ss, subsequently increased their syllable repertoires significantly. Ss reared in noise to weaning at 40 days, again partly deaf, achieved a normal repertoire size when stimulated with a singing adult. Without such stimulation the repertoire was significantly reduced, showing that canary song is not fully innate. Although abnormal, the song of deaf canaries retained more species-specific features than did the song of emberizine sparrows when the songs developed without auditory feedback. Results are interpreted in terms of a sensory template theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Regressive development in neuronal structure during song learning in birds

We investigated the development of spiny neurons in the lateral magnocellular nucleus of the anterior neostriatum before, during, and after song learning in male zebra finches (Taeniopygia guttata). The frequency of dendritic spines, dendritic field size, and branching characteristics were quantified at different ages in Golgi-stained tissue using a three-dimensional computerized tracing system. During development, overall spine frequencies increase between 3 and 5 weeks and decrease thereafter. In particular, spine frequencies of middle segments decrease significantly by 14% between 5 and 7 weeks posthatching (p = 0.017). A further reduction of 48% occurs between 7 weeks and adulthood (p < 0.001), resulting in a spine reduction of 56% on middle segments between 35 days of age and adulthood. In addition to the reduction of spine frequencies, we find regressive events also on some of the neuronal parameters that we have quantified. In general, dendrites of adult animals terminate closer to the cell body than those of 7-, 5-, or 3-week-old birds. Whereas no changes in segment length of first- and second-order dendrites have been identified, third-order dendrites end 19% closer to the cell body in adults than in younger birds (p < 0.024). Second-order dendrites in adult animals branch less frequently than in 3-week-old animals (35%, p = 0.017). There is also a trend of a smaller number of tertiary branches in adulthood compared with 3-week-old birds (41%, p = 0.060). The morphological changes may be related to the function of this nucleus and the sensitive phase for song acquisition.     

They''re playing our song: gene expression and birdsong perception

The locomotor stimulating effect of d-amphetamine in mice was counteracted by the administration of l-naloxone [(-)-naloxone], a known opiate receptor antagonist. Mice injected with amphetamine reached a peak locomotor activity within 30 min. When treated simultaneously with amphetamine and l-naloxone, these subjects showed low motility. Furthermore, when mice were treated not with l-naloxone but with its mirror image, d-naloxone [(+)-naloxone], a compound that by itself does not antagonize opiates and does not affect spontaneous motility, they showed no amphetamine-induced hyperactivity. The finding that an enantiomer of naloxone, with no opiate antagonist activity, is able to block the excitatory action of amphetamine, suggests the existence of a hitherto unknown mechanism of counteracting some of the effects of stimulants and euphoriants like amphetamine and cocaine.     

Song learning in brood-parasitic indigobirds Vidua chalybeata: song mimicry of the host species

Brood-parasitic village indigobirds, Vidua chalybeata, were bred in captivity and foster-reared by their normal host, red-billed firefinch, Lagonosticta senegala, or by an experimental foster species, Bengalese finch, Lonchura striata. Male indigobirds reared by Bengalese finches developed the songs of Bengalese finches, and males reared by firefinches developed songs of firefinches. Males copied their foster father only when they had lived with him long after independence (45 days post-fledging), while males separated normally at independence (22-24 days post-fledging) copied songs of other individuals and not songs of their foster father. Males reared by Bengalese finches showed no preference to learn firefinch song over songs of the experimental foster species or other control finch species even when they had lived with firefinches as companions from the time of fledging to independence. Males copied several song themes, acquired the same number of mimicry songs, and acquired their songs at the same age, whether reared by Bengalese finches or by firefinches. When they lived with other indigobirds, the male indigobirds copied mimicry songs of male indigobirds that mimicked the same foster species. We predicted mimicry-song specificity and repertoire size in experimental indigobirds from a hypothesis of an early developmental period when young indigobirds focus their attention on their foster parents, and a later period when they direct their attention to other birds with similar songs. The predictions, based on field observations of wild birds, were that (1) males reared by a novel foster species other than the normal host would learn the song of that foster species, and (2) males that left their foster parents at the normal time of independence would copy the songs of other individuals, including other adult indigobirds that mimicked the same foster species. Begging calls of young indigobirds did not mimic the calls of young firefinches. Indigobirds reared alone, or with young of the normal host or of the experimental foster species, all developed begging calls in adult song that resembled their own begging as nestlings and fledglings, and only males that heard other adult indigobirds with firefinch-mimicry begging developed firefinch begging in their song. The incorporation of the innate begging calls as well as the learned begging calls into adult song, and the modification of the song themes of their individual song models, suggest that song development involves processes in addition to copying the songs of their own foster species and of older adult male indigobirds with songs like their own foster parents. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.     

Neuronal circuit regulation of the hypothalamo-pituitary-adrenocortical stress axis

The hypothalamo-pituitary-adrenocortical (HPA) axis is the primary modulator of the adrenal glucocorticoid stress response. Activation of this axis occurs by way of a discrete set of neurons in the hypothalamic paraventricular nucleus (PVN). The PVN neuron appears to be affected by multiple sources, including (1) brainstem aminergic/peptidergic afferents; (2) blood-borne information; (3) indirect input from limbic system-associated regions, including the prefrontal cortex, hippocampus, and amygdala; and (4) local-circuit interactions with the preoptic-hypothalamic continuum. Analysis of the literature suggests that different classes of stressor employ different stress circuits. Severe physiologic ("systemic") stress appears to trigger brainstem/circumventricular organ systems that project directly to the paraventricular nucleus. In contrast, stressors requiring interpretation with respect to previous experience ("processive" stressors) reach the PVN by way of multisynaptic limbic pathways. Limbic regions mediating processive stress responses appear to have bisynaptic connections with the PVN, forming intervening connections with preoptic/hypothalamic GABAergic neurons. Stressors of the latter category may thus require interaction with homeostatic information prior to promoting an HPA response. The HPA stress response thus appears to be a product of both the physiologic importance of the stimulus and the specific pathways a given stimulus excites.     

Role of memory in concept learning.

Studies manipulating variables in the attempt to produce different memory requirements in concept learning are reviewed. Many of them have tested Underwood's theoretical position of response contiguity. Performance is generally improved by increasing the availability of previous stimulus information. The degree to which instances of the same concept occur contiguously directly affects acquisition of the concept. Attempts to demonstrate inferior performance with spaced practice have not been successful, although procedural problems make any conclusion tentative. There is some suggestion that memory effects could be classified as proactive and retroactive inhibition. A basic problem concerns the indirect type of question posed by investigators. (36 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of attention in implicit learning.

Previous research has shown that implicit learning of a serial pattern in a reaction time (RT) task is eliminated or reduced when the task is performed concurrently with a tone-counting task. These results led to the inference that implicit learning requires attentional capacity. Two experiments tested the alternative hypothesis that the tone-counting task disrupts learning by preventing consistent organization of the sequence. The tone-counting condition was compared with a condition with additional attentional demands, but no disruption of organization, and with a condition with no additional attentional demands, but disruption of organization. The results were consistent with the organizational hypothesis. It is argued that learning depends on practicing consistently organized runs of trials, that shifts of attention may determine how the runs are organized, and that the relation between attention and learning depends more on organization and intention than on capacity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Demand theory of gene regulation. I. Quantitative development of the theory

Induction of gene expression can be accomplished either by removing a restraining element (negative mode of control) or by providing a stimulatory element (positive mode of control). According to the demand theory of gene regulation, which was first presented in qualitative form in the 1970s, the negative mode will be selected for the control of a gene whose function is in low demand in the organism's natural environment, whereas the positive mode will be selected for the control of a gene whose function is in high demand. This theory has now been further developed in a quantitative form that reveals the importance of two key parameters: cycle time C, which is the average time for a gene to complete an ON/OFF cycle, and demand D, which is the fraction of the cycle time that the gene is ON. Here we estimate nominal values for the relevant mutation rates and growth rates and apply the quantitative demand theory to the lactose and maltose operons of Escherichia coli. The results define regions of the C vs. D plot within which selection for the wild-type regulatory mechanisms is realizable, and these in turn provide the first estimates for the minimum and maximum values of demand that are required for selection of the positive and negative modes of gene control found in these systems. The ratio of mutation rate to selection coefficient is the most relevant determinant of the realizable region for selection, and the most influential parameter is the selection coefficient that reflects the reduction in growth rate when there is superfluous expression of a gene. The quantitative theory predicts the rate and extent of selection for each mode of control. It also predicts three critical values for the cycle time. The predicted maximum value for the cycle time C is consistent with the lifetime of the host. The predicted minimum value for C is consistent with the time for transit through the intestinal tract without colonization. Finally, the theory predicts an optimum value of C that is in agreement with the observed frequency for E. coli colonizing the human intestinal tract.     

Role of stimulus ambiguity in conditional learning.

Three experiments using rats and the conditioned emotional response procedure examined the notion that when a conditioned stimulus (CS) is paired with a reinforcer (US), that CS must be ambiguous if the CS–US association is to become the target of conditional control. CS ambiguity was manipulated by varying whether the CS had been preexposed prior to conditioning. In Experiments 1 and 2, it was demonstrated that a cue that accompanied pairings of a CS and shock acquired conditional control over the CS–shock association when that CS had been preexposed, but not when it was novel. The measure of conditional control in Experiments 1 and 2 was the ability of the (conditional) cue to enhance responding to the target CS. Experiment 3 used a blocking procedure to show that this enhancement reflected an amplification of the target CS's effective associative strength. These findings extend existing knowledge of the conditions required for conditional cue formation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of the ZWILLE gene in the regulation of central shoot meristem cell fate during Arabidopsis embryogenesis

Postembryonic development in higher plants is marked by repetitive organ formation via a self-perpetuating stem cell system, the shoot meristem. Organs are initiated at the shoot meristem periphery, while a central zone harbors the stem cells. Here we show by genetic and molecular analyses that the ZWILLE (ZLL) gene is specifically required to establish the central-peripheral organization of the embryo apex and that this step is critical for shoot meristem self-perpetuation. zll mutants correctly initiate expression of the shoot meristem-specific gene SHOOT MERISTEMLESS in early embryos, but fail to regulate its spatial expression pattern at later embryo stages and initiate differentiated structures in place of stem cells. We isolated the ZLL gene by map-based cloning. It encodes a novel protein, and related sequences are highly conserved in multicellular plants and animals but are absent from bacteria and yeast. We propose that ZLL relays positional information required to maintain stem cells of the developing shoot meristem in an undifferentiated state during the transition from embryonic development to repetitive postembryonic organ formation.     

Self-regulated learning and college students' regulation of motivation.

This study extends current models of self-regulated learning by addressing 3 research questions, including what strategies do students use to regulate their motivation? is the use of these strategies dependent on contextual factors? how is motivational regulation related to other aspects of self-regulated learning and achievement? Self-report data were collected from 115 college students by using an open-ended questionnaire and Likert-style survey. Findings provide evidence that students regulate their level of effort in academic tasks by using a variety of cognitive, volitional, and motivational strategies; that students' reported use of these strategies varied across the 3 motivational problems with which they were presented; and that different aspects of students' motivational regulation were related positively to their goal orientation, use of some cognitive strategies, and course grade. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Time scales in motor learning and development.

A theoretical framework based on the concepts and tools of nonlinear dynamical systems is advanced to account for both the persistent and transitory changes traditionally shown for the learning and development of motor skills. The multiple time scales of change in task outcome over time are interpreted as originating from the system's trajectory on an evolving attractor landscape. Different bifurcations between attractor organizations and transient phenomena can lead to exponential, power law, or S-shaped learning curves. This unified dynamical account of the functions and time scales in motor learning and development offers several new hypotheses for future research on the nature of change in learning theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fli-1在肿瘤发生及发展中的作用

Friend白血病病毒插入位点1(Fli-1)是属于E26转化特异性因子(ETS)家族的转录因子,在造血干细胞、血管内皮细胞、淋巴细胞和恶性肿瘤细胞中表达,在血管内皮细胞生成和肿瘤细胞增殖过程中具有重要调节作用.血管内皮细胞不仅是正常血管生成的关键因素,而且在肿瘤的生长和转移中均需要新生血管的形成作为肿瘤进展的驱动因素.以Fli-1为治疗靶点,既可抑制肿瘤细胞的增殖,又可阻断肿瘤血管的形成,将成为治疗肿瘤的优秀靶点.因此,详细研究Fli-1结构与功能及其在恶性肿瘤中的表达情况,有助于进一步明确Fli-1在恶性肿瘤发生及发展中的作用.本文作者就Fli-1与肿瘤关系的研究进行综述.     

Role of ingestion in odor-toxicosis learning in the rat.

Conducted 2 experiments with 32 and 34 male Charles River albino rats, in which Ss evidenced aversions to an odor paired with toxicosis in both drinking and exploratory behavior tests. Ingestion during odor-toxicosis conditioning in Exp I resulted in stronger aversions only in tests involving drinking the same solution as had been ingested during training, despite the absence of enhanced aversions to the flavor of the solution used. This result is interpreted as evidence that Ss drinking during conditioning acquired aversions not only to the CS odor but also to additional cues arising from an interaction of the CS odor and the flavor of the ingested solution. Exp II showed that these interaction cues were not the result of a flavor imparted to the ingested substance by dissolved molecules of the odorizing agent. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of reinforcement in discrimination learning set in monkeys.

Analyzes the major theoretical explanations of learning-set (LS) formation in monkeys after reviewing empirical research on the role of reinforcement in LS formation. Studies showing that a reward can function to decrease as well as increase the probability of choosing an object cast doubt upon theories based on an automatic strengthening function of reward. Hypothesis or strategy selection theories avoid this problem by assuming hypotheses, rather than responses, are subject to reinforcement principles, but hypothesis theories are at best incomplete in their treatment of retention. A theory which assumes that LS formation results from between-problem stimulus generalization of feedback from expected rewards is consistent both with retention studies and with experiments on the function of reward in LS, suggesting that LS formation need not be considered a complex abstractive process. (94 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)