ISSN:0006-8977    

DOI:10.1159/000113575

出版商:S. Karger AG    

年代:1994

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000113576

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

A series of studies is described which in general aim to identify two sets of neural linkages in the brain and spinal cord of songbirds and non-songbirds, these avian types differing along a dimension of 'complexity of vocal communication'. One set of linkages is postulated to link the vocal system with the respiratory system, since birds, like humans, require controlled expiration in order to vocalize normally. The other set is thought to link the auditory system with the vocal system, at least in songbirds, because they are dependent upon auditory feedback for vocal learning. The systems and their linkages can be regarded as forming an 'auditory-vocal-respiratory axis', around which the animal's communication system evolves and revolves. The experimental strategy used was one which began at the periphery (the abdominal expiratory muscles), then progressively identified more central neural structures using retrograde transport methods in partial combination with recordings of single cell activity. The projections delineated by these methods were then defined in detail by anterograde tracing methods. The results of the studies confirmed the expectation that the vocal and respiratory systems have many neural elements in common. They also suggested that songbirds and non-songbirds possess similar neural pathways in the brainstem and spinal cord for the control of both vocalization and respiration but indicated that there may be significant differences between the two types of birds in the degree to which the telencephalon is able to modulate respiratory-vocal activity downstream. Thus, whereas there is a cascade of descending projections terminating upon syringeal and laryngeal motoneurons and expiratory premotor neurons in both songbirds and non-songbirds, the most rostral origin of this cascade is the telencephalic nucleus robustus archistriatalis in (male) songbirds but, apparently, the dorsomedial nucleus of the intercollicular complex of the midbrain (DM) in pigeons. Connectional studies of the auditory system in pigeons delineated a series of projections which originate in Field L2, the primary telencephalic auditory area, and leave the telencephalon via the nucleus archistriatum intermedium, pars medialis (Aivm), after traversing a minimum of three synapses within the telencephalon. The extratelencephalic projections of Aivm resemble those of deep layers of mammalian auditory neocortex, having terminations in close proximity to thalamic and midbrain auditory nuclei, but a projection upon DM is conspicuous by its absence. The way in which auditory input gains access to vocal control nuclei in non-songbirds, such as pigeons, thus remains to be determined.

ISSN:0006-8977    

DOI:10.1159/000113577

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Interconnections of forebrain auditory and vocal control nuclei were mapped in the budgerigar using pathway tracing techniques. The anatomical results indicate four circuits by which auditory information may influence the vocal motor system: (1) direct auditory thalamic projections from nucleus dorsomedialis posterior (DMP) to both the neostriatal higher vocal center (HVC) and robust archi-striatal nucleus (RA); (2) direct projections from a neostriatal projection field of DMP (i.e., MAN, the magnocellular nucleus of the neostriatum) to HVC and RA; (3) projections from DMP and other 'accessory' auditory thalamic nuclei to the ventral paleostriatum (VP), which in turn projects to MAN and RA; (4) projections to HVC from the lateral hyperstriatum ventrale (HV), which receives input from nucleus basalis (Bas) as well as from the oval nucleus of the HV (HVo), which receives direct input from RA. Lesion methods were used to evaluate the roles of auditory pathways in call learning and production. The results show that pathways associated with Bas are essential for call production in both adult and unfledged budgerigars, while VP efferents influence vocalization only in young, unfledged budgerigars. Lesions centered in either the primary auditory neostriatum (Field L2a) or the neostriatal area in receipt of Field L input (the ventrolateral neostriatum intermedium or NIVL) did not affect vocalization in juvenile or adult budgerigars.

ISSN:0006-8977    

DOI:10.1159/000113578

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Interconnections of forebrain auditory and vocal control nuclei were mapped in the budgerigar using pathway tracing techniques. The anatomical results indicate four circuits by which auditory information may influence the vocal motor system: (1) direct auditory thalamic projections from nucleus dorsomedialis posterior (DMP) to both the neostriatal higher vocal center (HVC) and robust archi-striatal nucleus (RA); (2) direct projections from a neostriatal projection field of DMP (i.e., MAN, the magnocellular nucleus of the neostriatum) to HVC and RA; (3) projections from DMP and other 'accessory' auditory thalamic nuclei to the ventral paleostriatum (VP), which in turn projects to MAN and RA; (4) projections to HVC from the lateral hyperstriatum ventrale (HV), which receives input from nucleus basalis (Bas) as well as from the oval nucleus of the HV (HVo), which receives direct input from RA. Lesion methods were used to evaluate the roles of auditory pathways in call learning and production. The results show that pathways associated with Bas are essential for call production in both adult and unfledged budgerigars, while VP efferents influence vocalization only in young, unfledged budgerigars. Lesions centered in either the primary auditory neostriatum (Field L2a) or the neostriatal area in receipt of Field L input (the ventrolateral neostriatum intermedium or NIVL) did not affect vocalization in juvenile or adult budgerigars.

ISSN:0006-8977    

DOI:10.1159/000316244

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Specialized neural circuitry has evolved in groups of birds where vocal learning is known to occur, such as in the oscine suborder of the Passeriformes (song-birds) and in the order Psittaciformes (parrots). These specializations are most prominent in the telencephalon, while the midbrain and medullary portions of the vocal control circuit are generally similar in all orders of birds. Specializations in songbirds have at least four components: 1) a set of distinct and interconnected vocal control nuclei in the forebrain; 2) unique connections between the auditory system and these vocal control nuclei; 3) the occurrence of receptors for sex steroid hormones in a subset of the vocal control nuclei; and 4) unique patterns in the distribution of various markers of the major classes of neurotransmitters within the vocal control nuclei. In the order Psittaciformes, as exemplified by budgerigars (Melopsittacus undulatus), it appears that neural specializations generally similar to those described in songbirds have evolved independently. Although anatomical studies have found a system of interconnected forebrain regions in budgerigars that are roughly similar to those described in oscines, detailed connectivity studies of this forebrain system suggest that it is only superficially similar to that of songbirds, and budgerigars also have unique connections between the auditory and motor systems. Also, analyses of the distribution of markers of neurotransmitter function in the budgerigar brain reveal patterns different from those described in songbird vocal control systems. This work suggests that songbirds and parrots have evolved separate neural ‘solutions’ to solve the problem of vocal plasticity. There are differences between these 'solutions' but also similarities that may be the result of convergent evolution. Although vocal behavior is learned in both songbirds and parrots, it differs in many respects. By taking advantage of this 'natural' experiment one can gain insight into the hormonal and neural events that mediate these different forms of vocal plasticity.

ISSN:0006-8977    

DOI:10.1159/000113579

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

This paper reviews the organizational principles and implications that have emerged from the analysis of HVc, a forebrain nucleus that is a major site of sensory, motor, and sensorimotor integration in the song control system of oscine passerine birds (songbirds). Anatomical, physiological, and behavioral data support the conclusion that HVc exists within a hierarchically organized system with parallel pathways that converge onto HVc. The organization of HVc is distributed and redundant, and its outputs exhibit broad divergence. A similar pattern of connectivity exists for neostriatum adjacent to HVc. This and other data support the hypothesis that the song system arose from an elaboration or duplication of pathways generally present in all birds. Spontaneous and auditory response activity is strongly correlated throughout HVc, with auditory responses exhibiting strong temporal modulation in a synchronized fashion throughout the nucleus. This suggests that the auditory representation of song is encoded in the synchronized temporal patterns of activation, and that the predominant selectivity for the individual's own song that is observed for HVc neurons results from interactions of auditory input with central pattern generators for song. Most, or all HVc neurons are recruited during singing. The auditory response and motor recruitment properties of individual HVc neurons have no simple relationship, and the spontaneous activity in HVc may build up in the seconds preceding a song. To the extent HVc participates in perceptual phenomena associated with song, production and perception are not tightly linked in adults but may be linked by shared developmental processes during periods of sensorimotor learning.

ISSN:0006-8977    

DOI:10.1159/000113580

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

This paper reviews the organizational principles and implications that have emerged from the analysis of HVc, a forebrain nucleus that is a major site of sensory, motor, and sensorimotor integration in the song control system of oscine passerine birds (songbirds). Anatomical, physiological, and behavioral data support the conclusion that HVc exists within a hierarchically organized system with parallel pathways that converge onto HVc. The organization of HVc is distributed and redundant, and its outputs exhibit broad divergence. A similar pattern of connectivity exists for neostriatum adjacent to HVc. This and other data support the hypothesis that the song system arose from an elaboration or duplication of pathways generally present in all birds. Spontaneous and auditory response activity is strongly correlated throughout HVc, with auditory responses exhibiting strong temporal modulation in a synchronized fashion throughout the nucleus. This suggests that the auditory representation of song is encoded in the synchronized temporal patterns of activation, and that the predominant selectivity for the individual's own song that is observed for HVc neurons results from interactions of auditory input with central pattern generators for song. Most, or all HVc neurons are recruited during singing. The auditory response and motor recruitment properties of individual HVc neurons have no simple relationship, and the spontaneous activity in HVc may build up in the seconds preceding a song. To the extent HVc participates in perceptual phenomena associated with song, production and perception are not tightly linked in adults but may be linked by shared developmental processes during periods of sensorimotor learning.

ISSN:0006-8977    

DOI:10.1159/000316246

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Vocal learning through imitation underlies both human speech acquisition and song acquisition in oscine birds; both processes depend on auditory information. In songbirds, a specialized forebrain pathway is responsible for producing the learned temporal and acoustic features of vocalizations, and auditory input reaches every level of this pathway. Nucleus robustus archistriatalis (RA) is the source of the final common output from this pathway; RA is topographically organized into subregions that control the syringeal, respiratory and other effectors involved in vocal production. The acoustic features of learned vocalizations are primarily produced by specific patterns and combinations of syringeal muscle activity, while the overall temporal structure is primarily under respiratory control. In RA, and other vocal control structures, the individual bird's own learned song (BOS) is the most effective stimulus for eliciting auditory responses. Some neurons are 'combination-selective' in that they respond maximally to stimuli consisting of sequences of syllables from song. The recording sites that respond selectively to BOS tend to be located in more ventral parts of RA, the subregion that projects to motor neurons controlling syringeal muscles. These observations do not distinguish between motor feedback and perceptual hypotheses about the function of auditory responses in vocal motor pathways but are consistent with the idea that such responses may reflect a specific pattern of interaction between sensory and motor events that reflects vocal learning.

ISSN:0006-8977    

DOI:10.1159/000113581

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Several landmark discoveries have shaped the recent study of brain substrates for birdsong. The failure of deaf birds to reproduce a song from memory lent support for the concept of a song template. An attempt to test this idea resulted in the discovery of lateralization of song control. Search for the brain sites of lateralization and auditory control of voice led to the discovery of the main song control nuclei. Neurophysiological studies have unequivocally shown that auditory information reaches the song control system, but the exact pathway by which the song control system receives auditory inputs needs further investigation. The finding that lesions of the lateral magnocellular nucleus of the anterior neostriatum or area X affect song development in young birds but not the maintenance of song in adults suggested a role of the anterior forebrain pathway to RA in song learning. Another area of research in which much progress has been made concerns the relationships between the vocal and respiratory systems. The archistriatal and midbrain vocal nuclei innervate some of the respiratory centers in the medulla. The old questions of 'mini-breath' during fast singing and independent control of the two sides of the syrinx have been resolved. Finally, comparisons of the vocal and auditory systems between taxa indicate that different groups may use different neural circuits to achieve similar vocal-auditory behavior.

ISSN:0006-8977    

DOI:10.1159/000113582

出版商:S. Karger AG    

年代:1994

数据来源: Karger