摘要:

AbstractLateral MAN (magnocellular nucleus of the anterior neostriatum) is a forebrain nucleus that is known to be importantly involved with vocal learning in juvenile male zebra finches only during a restricted period of the learning process: lesions of lMAN completely disrupt song behavior in zebra finches prior to 50 days of age but have little or no effect in older juvenile or adult birds. The development of lMAN, as of other song‐control regions, is delayed until the time that song behavior is being learned. Lateral MAN undergoes a substantial loss of neurons between 25 and 55 days of age, a time that encompasses initial stages of vocal production as well as the interval during which lMAN lesions become ineffective. In this study, we measured both the time course of neuronal loss and the incidence of pyknotic cells within lMAN during the period of cell loss. There is a pronounced loss of neurons from lMAN between 20 and 35 days, after which the adult number of neurons is established. The incidence of pyknosis is greatest at 20 days, around the time when the loss of live cells is also most pronounced, suggesting that the loss of neurons from lMAN is attributable to cell death. The loss of neurons occurs well before lesions of lMAN become ineffective in disrupting vocal behavior. Thus the neurons remaining in lMAN after the period of cell loss apparently undergo a substantial change in function at the time lesions lose effectiveness (about 55–60 da

ISSN:0022-3034    

DOI:10.1002/neu.480200702

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe electric organ discharge (EOD) of several species of mormyrid fishes within the genusBrienomyrusis sexually dimorphic during the breeding season: the duration of the male's EOD is much longer than the duration of the female's (for a review see Hopkins, 1986). The mormyrid used here,Brienomyrussp., exhibits similar alterations in the duration of the triphasic EOD after treatment with testosterone, as do other members of this genus (for reviews see Bass, 1986a,b). In this experiment, animals were intraperitoneally implanted with pellets of either 11‐ketotestosterone or 17 a‐methyltestosterone, and the time course of the changes in the duration of each of the three phases of the EOD were quantified. Additionally, the time course of changes in the morphology of the electric organ, after testosterone treatment, was also quantified using electron microscopic techniques. The results suggest that the change in the duration of the first phase of the EOD is due exclusively to the change in the thickness of the electrocyte body: this is consistent with a model proposed by Bennett and Grundfest (1961) for the electrogenesis of a triphasic EOD. Changes in the duration of the second and third phases of the EOD are highly correlated with changes in the surface area of the posterior and anterior faces of the electrocyte, respectively. The results support the hypothesis that gonadal steroid hormone‐induced changes in the EOD are due to structural changes in the electrocyte's membranes, and that all of the observed changes in the discharge of this system can be explained by the action of steroid hormones on the peripheral target cells (electroc

ISSN:0022-3034    

DOI:10.1002/neu.480200703

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe effects of a variety of neuromodulator substances on rhythmic motor output and activity in neurons in the feeding circuitry ofLymnaea stagnaliswere examined. Each neuromodulator produced a unique combination of effects at different levels in the network: i.e., pattern‐generating interneurons (N1, N2, and N3), an identified higher‐order interneuron (cerebral giant cell, CGC), and buccal motoneurons. 5‐Hydroxytryptamine, acetylcholine, and FMRFamide all inhibited rhythmic motor activity. However, this was achieved in different ways. Dopamine changed the nature of rhythmic activity from one in which N2 interneuronal activity was predominant (“N2 rhythm”) to a feeding rhythm. Dopamine was the only substance capable of activating the feeding rhythm. Activity in the CGC was increased by 5‐hydroxytryptamine, dopamine, and acetylcholine and reduced by FMRFamide. Differential responses in buccal motoneurons were also observed. The results are discussed in relation to previous work on other species and also in terms of the selection of different patterns of motor output by neur

ISSN:0022-3034    

DOI:10.1002/neu.480200704

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractDuring song learning in birds, neurons are added to some song nuclei and lost from others. Previous studies have been unable to distinguish whether these neural changes are uniquely associated with memorizing a song model (sensory acquisition) or vocal practice (sensorimotor learning). In this study we measured changes in neuron number within song nuclei of swamp sparrows, a species in which the two phases of song learning are nonoverlapping. Male swamp sparrows were collected as hatchlings and tape‐tutored from approximately 22 to 62 days of age. Swamp sparrows memorize about 60% of their song material during this period, but do not begin practicing this learned material until approximately 275 days of age. Birds were sacrificed at 23, 41, 61, 71, 274, or 340 days of age. During sensory acquisition, neuron number increased drastically in both the caudal nucleus of the ventral hyperstriatum (HVc) and Area X. The period of sensorimotor learning was not associated with any further changes in neuron number within these regions. We were unable to detect any significant changes in neuron number within the magnocellular nucleus of the neostriatum or the robust nucleus of the archistriatum during either stage of song learning. These results raise the possibility that ongoing addition of HVc and Area X neurons may encourage, and thereby temporally restrict, song acquisitio

ISSN:0022-3034    

DOI:10.1002/neu.480200705

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480200701

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY