Vocalization evoked from the optic lobe of a songbird

Vocalizations from songbirds have been evoked by electrical stimulation of the torus. These vocalizations resemble the normal alarm and scolding calls of the species. The torus of the birds appears to correspond functionally and anatomically to the mammalian central gray matter.     

Sexual difference in pattern of hormone accumulation in the brain of a songbird

After adult zebra finches (Poephila guttata) received injections of tritiated testosterone, fewer hormone-concentrating cells were found in females than in males in two brain regions involved in song: hyperstriatum ventrale pars caudale and magnocellular nucleus of the anterior neostriatum. In some other regions, no sexual difference was detected. It is, therefore, possible that sex differences in the sensitivity of specific neural populations to hormones underlie the striking anatomical dimorphism observed in neural regions controlling song.     

Impacts of a global climate cycle on population dynamics of a migratory songbird

Progress toward understanding factors that limit abundances of migratory birds, including climate change, has been difficult because these species move between diverse locations, often on different continents. For black-throated blue warblers (Dendroica caerulescens), demographic rates in both tropical winter quarters and north temperate breeding grounds varied with fluctuations in the El Ni?o Southern Oscillation. Adult survival and fecundity were lower in El Ni?o years and higher in La Ni?a years. Fecundity, in turn, was positively correlated with subsequent recruitment of new individuals into winter and breeding populations. These findings demonstrate that migratory birds can be affected by shifts in global climate patterns and emphasize the need to know how events throughout the annual cycle interact to determine population size.     

Population dynamical consequences of climate change for a small temperate songbird

Predicting the effects of an expected climatic change requires estimates and modeling of stochastic factors as well as density-dependent effects in the population dynamics. In a population of a small songbird, the dipper (Cinclus cinclus), environmental stochasticity and density dependence both influenced the population growth rate. About half of the environmental variance was explained by variation in mean winter temperature. Including these results in a stochastic model shows that an expected change in climate will strongly affect the dynamics of the population, leading to a nonlinear increase in the carrying capacity and in the expected mean population size.     

Reproductive effort, molting latitude, and feather color in a migratory songbird

Toward the end of the breeding season, migratory songbirds face crucial tradeoffs between the timing of reproduction, molt, and migration. Using stable hydrogen isotopes, we show that male American redstarts investing in high levels of reproduction late in the season adopt a unique strategy of combining molt and migration. Tail feathers molted during migration also reflect less orange-red light, indicating reduced carotenoid concentration. Thus, we show how reproduction in a migratory animal can influence both life history strategies (location of molt) and social signals (feather color) during subsequent periods of the annual cycle.     

Linking breeding and wintering ranges of a migratory songbird using stable isotopes

We used the natural abundance of stable isotopes (carbon and hydrogen) in the feathers of a neotropical migrant songbird to determine where birds from particular breeding areas spend the winter and the extent to which breeding populations mix in winter quarters. We show that most birds wintering on western Caribbean islands come from the northern portion of the species' North American breeding range, whereas those on more easterly islands are primarily from southern breeding areas. Although segregated by breeding latitude, birds within local wintering areas derive from a wide range of breeding longitudes, indicating considerable population mixing with respect to breeding longitude. These results are useful for assessing the effects of wintering habitat loss on breeding population abundances and for predicting whether the demographic consequences will be concentrated or diffuse.     

Reproductive development in a female songbird: differential stimulation by quality of male song

Female canaries exposed to playback of large repertoires of male songs built nests faster and laid more eggs than did those females exposed to smaller song repertoires: females are attentive to attributes of male song, and their choices have played a role in the evolution of oscine singing behaviors.     

A specialized forebrain circuit for vocal babbling in the juvenile songbird

Young animals engage in variable exploratory behaviors essential for the development of neural circuitry and adult motor control, yet the neural basis of these behaviors is largely unknown. Juvenile songbirds produce subsong-a succession of primitive vocalizations akin to human babbling. We found that subsong production in zebra finches does not require HVC (high vocal center), a key premotor area for singing in adult birds, but does require LMAN (lateral magnocellular nucleus of the nidopallium), a forebrain nucleus involved in learning but not in adult singing. During babbling, neurons in LMAN exhibited premotor correlations to vocal output on a fast time scale. Thus, juvenile singing is driven by a circuit distinct from that which produces the adult behavior-a separation possibly general to other developing motor systems.     

Corticosterone regulation of tryptophan hydroxylase in midbrain of the rat

The tryptophan hydroxylase activity in the rat midbrain decreases after adrenalectomy and is restored by treatment with corticosterone. Cycloheximide, adminiistered intracisternally, prevents the restoration of the enzyme activity by corticosterone. Cycloheximide administration to adrenalectomized rats resutlts in a further decrease in the enzyme activity. an indication that the enzyme has a rapid turnover even in the absence of corticosterone.     

Electrical stimulation of the midbrain mediates metastatic tumor growth

Pulmonary metastases were counted 10 days after female rats received tail-vein injections of Walker-256 carcinosarcoma cells. Previous observations that halothane anesthesia plus hind-limb amputation increases the number of metastases were confirmed. Amputation under the analgesia of electrical stimulation of the midbrain was found to increase metastatic activity. However, the stimulus-produced analgesia alone also increased the number of metastases. Systemically administered naloxone blocked the analgesic effect of midbrain stimulation but did not block the increase in the number of pulmonary metastases.     

Lysergic acid diethylamide: sensitive neuronal units in the midbrain raphe

Units in areas of the midbrain rich in neurons containing serotonin respond to parenteral injections of d-lysergic acid diethylamide by a reversible cessation of spontaneous activity. The dose required is at or below threshold for gross behavioral effects. An inhibition of neurons containing serotonin after administration of d-lysergic acid diethylamide could account for the decreased metabolism of serotonin produced by this drug.     

Serotonin: release in the forebrain by stimulation of midbrain raphé

Electrical stimulation of the midbrain raphé, an area in which neuronal perikarya containing serotonin are aggregated, produces an increase in 5-hydroxyindoleacetic acid and a decrease in serotonin in the forebrain. These changes indicate that serotonin in the brain can be released via a specific neural pathway, namely, the system of axons projecting into the forebrain from serotonin-containing neurons in the midbrain raphé.     

Biting attack elicited by stimulation of the ventral midbrain tegmentum of cats

An area in the ventral midbrain tegmentum has been discovered in which electrical stimulation elicits biting attack. The midbrain sites from which attack was elicited correspond well with the zone in the midbrain tegmentum where degeneration was previously observed after lesions were made in lateral hypothalamic attack sites.     

Sonic hedgehog control of size and shape in midbrain pattern formation

Little is known about how patterns of cell types are organized to form brain structures of appropriate size and shape. To study this process, we employed in vivo electroporation during midbrain development to create ectopic sources of Sonic Hedgehog, a signaling molecule previously shown to specify different neuronal cell types in a concentration-dependent manner in vitro. We provide direct evidence that a Sonic Hedgehog source can control pattern at a distance in brain development and demonstrate that the size, shape, and orientation of the cell populations produced depend on the geometry of the morphogen source. Thus, a single regulatory molecule can coordinate tissue size and shape with cell-type identity in brain development.     

Visual discrimination of movement: midbrain or forebrain?

Monkeys whose optic chiasm and forebrain commissures had been sectioned and control monkeys with only the optic chiasm cut were tested for interocular transfer of discriminations based on direction of movement. Only the control animals showed transfer to the untrained eye, which suggests that discrimination of movement, like pattern, is a function strongly dependent on the cortex.     

Interaural phase coding in auditory midbrain: influence of dynamic stimulus features

A laterally located sound source stimulates the two ears at slightly different times, generating interaural phase disparities (IPDs) that are used for sound localization. Under natural conditions, such interaural cues are likely to be constantly changing, or dynamic. In the inferior colliculus of gerbils and cats, the nonlinearities in the coding of dynamic interaural phase cues are demonstrated. Responses to ecologically realistic phase cues are more reflective of the change of IPD than of the absolute IPDs over which that change occurs. This observation is inconsistent with the established view that directional information is coded in terms of absolute IPD.     

Steroid-sensitive single neurons in rat hypothalamus and midbrain: identification by microelectrophoresis

Minute amounts of Na-dexamethasone-21-phosphate administered by microelectrophoresis to the immediate extracellular environment promptly suppressed electrical activity of 15 out of 115 hypothalamic and mesencephalic neurons, the effect being readily reversible. Such neurons marked with fast green were found to lie in circumscribed areas of the periventricular gray of the third ventricle and aqueduct, and may represent a site of action of adrenocortical steroids in the regulation of corticotrophin releasing factor and/or adrenocortico-tropin secretion by negative feedback.     

Neuronal analysis of wave form in the time domain: midbrain units in electric fish during social behavior

A fish of the genus Eigenmannia responds differently to a neighboring conspecific fish with a slightly higher frequency of the electric organ discharge than its own than to one with a slightly lower such frequency than its own. When the two frequencies are beating against each other the special wave shape of the electric organ discharge leads to asymmetries of the beat pattern which are distinct for the two cases. Midbrain neurons, called "deltaF recoders," sign and magnitude of the frequency difference on the basis of these patterns. that is, in the time rather than the frequency domain.     

Cells related to fighting behavior recorded from midbrain central gray neuropil of cat

Cells were recorded in the midbrain central gray neuropil of the cat that responded with action potentials only during fighting behavior and not while the cat was resting or while control manipulations were performed. Some other cells in the same region responded maximally during fighting, and all cells responded to at least one manipulation. Brain stimulation at sites of cells related to fighting caused the animals to hiss.