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PubMed1978

The organization of neocortical projections from the ventroposterior thalamic complex in the marsupial brush-tailed possum, Trichosurus vulpecula: a horseradish peroxidase study.

Retrograde transport of horseradish peroxidase (HRP) was used to determine the extent and some of the organizational details of the cortical projection of the ventroposterior thalamic complex (VP) in the marsupial brush-tailed possum, Trichosurus vulpecula. The cortical projection field of VP is coincident with SI as determined by electrophysiological methods, and would appear not to overlap fully the primary motor cortex. Thus, in Trichosurus it appears that the motor and somatic sensory cortical regions are not fully congruent, unlike those of the American opossum, Didelphis, which are. Each division of VP projects discretely, in a non-overlapping manner, to various regions within SI. The ventrolateral subdivision or VPL projects medially and in a strict homotypic manner, though the proportion of VPL cells projecting to cortex is subject to a large amount of variation. The dorsomedial division of VP or VPM projects uniformly to cortex from all areas of that subnucleus, but the strict homotypy characteristic of VPL's projection was not as apparent. VPM also projects to two distinct regions within its cortical field. The posteromedial division of VP or VPP projects to an area of cortex that receives no other VP input but, on the basis of cortical mapping studies, appears to belong to SI. Projections from VPL (and presumably from VPM) to a small area of cortex in the extreme posterolateral part of the VP field correspond to the position expected for, and electrophysiologically confirmed to be, SII.

Animals↗
PubMed1993

Topographic organization of corticospinal projections from the frontal lobe: motor areas on the lateral surface of the hemisphere.

We examined the topographic organization of corticospinal neurons in the primary motor cortex and in the two premotor areas on the lateral surface of the hemisphere [i.e., the dorsal premotor area (PMd) and the ventral premotor area (PMv)]. In two macaques, we labeled corticospinal neurons that project beyond T7 or S2 by placing crystals of HRP into the dorsolateral funiculus at these segmental levels. In another seven macaques, we labeled corticospinal neurons that project to specific segmental levels of the spinal cord by injecting the fluorescent tracers fast blue and diamidino yellow into the gray matter of the cervical and lumbosacral segments. In one set of experiments (n = 2), we defined the representations of the arm and leg in each cortical motor area by injecting one of the two fluorescent tracers into lower cervical segments (C7-T1) and the other fluorescent tracer into lower lumbosacral segments (L6-S1) of the same animal. In another set of experiments (n = 5), we defined the representations of distal and proximal parts of the forelimb in each cortical motor area by injecting one of the two fluorescent tracers into lower cervical segments (C7-T1) and the other tracer into upper cervical segments (C2-C4) of the same animal. In the primary motor cortex and the PMd, cortical regions that project to lower cervical segments were largely separate from those that project to lower lumbosacral segments. In the PMv, few neurons were labeled after tracer injections into lower cervical segments or lower lumbosacral segments. However, corticospinal neurons were labeled in the PMv after tracer injections into upper cervical segments and after HRP placement in the dorsolateral funiculus at T7. The region of the PMv that projects to upper cervical segments was separate from that which projects below T7. Cortical regions that project to upper and lower cervical segments of the spinal cord overlapped considerably in the primary motor cortex and in the PMd. Despite this overlap, we found that the regions of the primary motor cortex and PMd that project most densely to upper cervical segments were largely separate from those that project most densely to lower cervical segments. Furthermore, we found two separate regions within area 4 that send corticospinal projections primarily to the lower cervical segments. One of these regions was located within the classical "hand" area of the primary motor cortex. The other was located at the medial edge of arm representation in the primary motor cortex.(ABSTRACT TRUNCATED AT 400 WORDS)

Amidines↗
PubMed1995

The projection from the primary motor and somatic sensory cortex to the basilar pontine nuclei. A detailed electrophysiological and anatomical study in the rat.

The projections from the primary motor and somatic sensory cortex onto the basilar pontine grey were studied in Wistar Rats injecting microvolumes of WGA-HRP solution in sites of the motor and sensory cortex electrophysiologically identified. The main results may be summarized as follows. (a) The projections from both the motor and sensory cortex were found as rostrocaudally oriented columns of terminals in the basilar pontine nuclei. The projection from the motor cortex extended to all over the rostrocaudal extension of the basilar pontine nuclei. To a rostrocaudal shift of the pontine projection field correspond a rostrocaudal displacement in the motor area. The projection from the sensory cortex was mainly restricted to the caudal two thirds of the basilar pontine nuclei, though the hindlimb region of the sensory cortex also showed a discrete representation in the rostral third of the basilar pontine nuclei. (b) The terminal fields of the motor and sensory cortex were segregated except those in the caudal pontine level, which come from the projection of the hindlimb cortical regions. (c) Within the terminal fields of the projections from the motor as well as from the sensory cortex a clearcut topographical arrangement was observed between the projections of cortical areas controlling the head, the forelimb and the hindlimb regions. (d) Within the location of these major subdivisions, the representations of individual body segments were overlapped for a little part ("convergent zones"), whereas the greater part of their projection zones was selective of each cortical field ("private zones"). In conclusion, the present study showed that the projections from the motor and sensory cortex to the basilar pontine nuclei are arranged with a very precise somatotopical organization.

Animals↗
PubMed1994

A shotgun marriage--community health workers and government health services. Qualitative evaluation of a community health worker project in Khayelitsha.

In 1988 the Western Cape Regional Services Council (RSC) initiated a community health worker (CHW) project in Khayelitsha in order to extend its preventive services to people in the community and promote 'community upliftment'. An evaluation of this project was undertaken in 1991 and 1992 in order to examine the potential of this local health authority-run CHW project to be an appropriate primary health care model. Qualitative research methods were used to explore the nature of the work done by the CHWs, whether they were accepted in their communities, and whether the project functioned as part of an integrated health service infrastructure in Khayelitsha. The CHWs were found to provide the basis for a potentially effective, community-responsive service. However, several structural problems mitigated against this service. Relations between the CHWs and nurses in all the formal public health services in the area were superficial and fraught with problems. There were significant differences and conflicting policies between the RSC's CHW project and other neighbouring non-government CHW projects, and these posed various threats to both the RSC and the non-government projects. One of the most serious of these differences was that the RSC project had no structures or plans for community involvement in the running of the project. Before a CHW project is initiated, several critical issues need to be carefully considered and discussed with all the relevant stakeholders. Furthermore, CHWs need to be flexible, and accountable to the communities in which they work. Before employing CHWs, formal public health authorities need to consider carefully whether they are able to meet these criteria.

Community Health Services↗
PubMed1996

The incidence and prevalence of AIDS and prevalence of other severe HIV disease in England and Wales for 1995 to 1999: projections using data to the end of 1994.

Projections of the future incidence of AIDS cases are needed for planning purposes, to help set research priorities, and to describe the most likely pattern of transmission of HIV infection in the past that underlies the observed and projected incidence of AIDS. Earlier reports of projections for England and Wales were published in 1988, 1990, and 1993. During 1995 a group of experts has worked, using AIDS case reports to the end of December 1994, to make new projections to the end of 1999. The expert group concludes that, after adjustment for underreporting, there will be between 1840 and 2300 new cases of AIDS in England and Wales in 1997, and between 1760 and 2455 new AIDS cases in 1999. For planning purposes, a figure of 2025 new AIDS cases is projected for 1997, and 2010 for 1999. The planning projections for new AIDS cases in 1997 and 1999 among the main exposure categories, after adjustment for underreporting, are as follows: homo/bisexual males 1305 and 1235, people exposed heterosexually 490 and 525, and injecting drug users 140 and 155. Between 1995 and 1999, it is expected that new AIDS cases may fall by 7% in homo/bisexual males, and rise by 25% in the heterosexual exposure category and by 29% in injecting drug users. The incidence of AIDS in the children of mothers infected with HIV is expected to rise steadily from 30 new cases in 1994 to 45 in 1997 and 55 in 1999. New cases in recipients of contaminated blood or blood factors are expected to fall to 35 in 1997 and 30 in 1999, compared with a peak 10 years earlier of over 70 new cases each year. It is projected that 4010 AIDS cases will be alive in England and Wales at the end of 1999, and that the same number of people will be alive with other forms of severe HIV disease. Since 1989 the proportion of reported AIDS cases who live in the NHS Thames regions has remained constant at between 70% and 75%. We expect this concentration of AIDS cases in the south east, particularly within London, to remain unchanged. Compared with the report published in June 1993, the planning projections for 1997 are 37% lower for cases acquired heterosexually, and the upper boundary of the range in this exposure category has fallen from 1140 to 495. The reduction in the planning projection has resulted from a substantial decline in the rate of increase in the number of new AIDS cases arising each year from heterosexual exposure. The range of uncertainty has narrowed largely because more extensive seroprevalence data are now available. For homo/bisexual males, the planning projection for 1997 has fallen by 3%, because the 1993 report presented an over optimistic view of the extent to which patients received treatment and prophylaxis before the onset of AIDS, since such management became available in 1988. Unlike the 1993 working group, the 1995 working group has access to data from several years on the uptake of treatment and prophylaxis given before the diagnosis of AIDS. It is estimated that about 21,900 adults (range 20,400 to 23,400) were infected with HIV in England and Wales at the end of 1993. This total includes 12,350 who had been infected through male homosexual exposure, 2050 men and women infected through injecting drug use, 6800 men and women infected through heterosexual exposure, and about 3000 adults alive with AIDS. Various data indicate that HIV transmission among homo/bisexual men has been substantial since 1989. Use of data from the unlinked anonymous HIV prevalence monitoring programme suggest that between 500 and 1000 HIV infections due to homosexual male exposure occurred each year in 1992 and 1993. Should HIV transmission continue at this level, a high incidence of AIDS within the homo/bisexual male community will be inevitable for many more years. Most HIV infections and AIDS cases due to heterosexual exposure are thought to have been acquired abroad. The future of the epidemic in this exposure category is therefore unclear.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Organisation of the tectorotundal and SP/IPS-rotundal projections in the chick.

The organisation of the neural projections from the optic tectum and pretectal nuclei complex, n. subpretectalis / n. interstitio-pretecto-subpretectalis (SP/IPS), to the nucleus rotundus (Rt) in chicks was studied by using retrograde tracing techniques. After the injection of fluorescent retrograde tracers, rhodamine-conjugated latex microspheres, fluorescein-conjugated latex microspheres, True Blue, Fluoro-Gold, or rhodamine B isothiocyanate, into different regions of Rt and its middorsal extension, the nucleus triangularis (T), the distribution of retrogradely labelled neuronal cell bodies in the tectum and pretectal nuclei was assessed. Both the ipsilateral and contralateral tectorotundal projections were found to be organised topographically in as much as different sublaminas of the stratum griseum centrale (SGC) project in an orderly manner to Rt and T. The deepest stratum of SGC overlapping into the stratum album centrale projects to T. Deep SGC projects to the dorsal Rt and superficial SGC to the ventral Rt. A band running through the centre of Rt receives input from the central sublamina of SGC, and the caudal central Rt receives input from a deeper sublamina than does the rostral central Rt. The SP/IPS projects to the ipsilateral Rt only and the projection order is dorsal SP to dorsal Rt, ventral SP to ventral Rt and middle SP to the central band of Rt. The neurones in IPS and the nucleus of the tractus tectothalamicus project to T. Thus, Rt and T receive topographically both tecto- (excitatory) and SP/IPS- (inhibitory) projections. The possible functional implications for parallel information processing in these projections are discussed.

Animals↗
PubMed1998

The effects of x-axis vertebral translation on projected y-axis vertebral rotation.

BACKGROUND: Few studies have quantified the projection/distortion errors that occur in anteroposterior (AP) radiographs. OBJECTIVES: To quantify the projection/distortion errors on AP radiographs caused by lateral translation of the vertebrae. To demonstrate the effect of vertebral shape on projection errors. STUDY DESIGN: Three models of increasing complexity were constructed to document the distortion. Model 1 consisted of three metal pins embedded in a piece of metal tubing that was X-rayed in three positions. Model 2, a simple model of the X-ray beam mounted on a wooden platform, allowed for translation of a vertebral model in a simulated X-ray beam and the measurement of projected points of contact between the model and rays of the simulated beam. Model 3 is a computer simulation of the X-ray beam in which a vertebral model was translated laterally to varying locations. The projected points of contact between the simulated rays and the vertebral body margins and lamina junction were measured. Model 3 also showed that vertebral body shape has a large effect on the projected axial rotation. Two other simple models were created and discussed in relation to shape-dependent projection errors. RESULTS: X-axis translation results in projected y-axis rotation. Increasing magnitudes of x-axis vertebral translation results in increasing magnitudes of projected y-axis vertebral rotation. The projected rotation is also influenced by vertebral shape. CONCLUSION: We have shown that three-dimensional lateral translation projects as axial rotation on the AP radiograph. Projection error is largely influenced by the shape of the object and by the increasing obliquity of the rays of the X-ray beam. This would seemingly create confusion and invalidate spinal listings of vertebral position obtained from the AP radiographic image.

Axis, Cervical Vertebra↗
PubMed1998

Patterns of brainstem projection to the thalamic reticular nucleus.

To understand better how the brainstem may influence thalamocortical activity, we have examined the projection patterns of different brainstem nuclei to the thalamic reticular nucleus. Iontophoretic injections of biotinylated dextran were made into various nuclei of the brainstem (superior colliculus, periaqueductal grey matter, parabrachial nucleus, pedunculopontine tegmental nucleus, laterodorsal tegmental nucleus, substantia nigra, ventral tegmental area, and locus coeruleus) of Sprague-Dawley rats by using stereotaxic coordinates. Our results show that afferents from each brainstem nucleus make distinct zones within the reticular nucleus. For example, the superior colliculus projects largely to the dorsal parts of the reticular nucleus, whereas the pedunculopontine nucleus projects to the ventral parts of the reticular nucleus. The substantia nigra, on the other hand, projects to the ventrolateral edge of the reticular nucleus. We also examined the distribution of these brainstem afferents within the dorsal thalamus and compared these distributions with those seen in the reticular nucleus. We found three different patterns. First, a given brainstem nucleus projects to a particular dorsal thalamic nucleus as well as to the corresponding, functionally associated, reticular sector (e.g., from the substantia nigra). Second, a given brainstem nucleus projects to a particular dorsal thalamic nucleus but not to the corresponding reticular sector (e.g., from the superior colliculus). Finally, a given brainstem nucleus projects to a given reticular sector but not to the corresponding dorsal thalamic nucleus (e.g., from the midbrain reticular nucleus). In general, our results indicate that various brainstem nuclei project to particular territories of the thalamic reticular nucleus. Through these reticular projections, brainstem nuclei may influence distinct thalamocortical pathways in addition to those that are influenced by their direct projection to the dorsal thalamus.

Animals↗
PubMed1998

Projecting the impact of AIDS on mortality.

OBJECTIVE: To illustrate the magnitude of the impact of AIDS on projections of mortality, to explain the reasons for the differences in projections by major international organizations and to provide a simple approach to estimating the impact of AIDS on life expectancy. RESULTS: AIDS has already had significant impacts on mortality in a number of countries in the developing world and this impact is expected to grow substantially in the next 10 years. By 2005 the population of the most severely affected countries in Africa will be 13-59 million less than it would have been without AIDS. Life expectancy may decline by as much as 27% in these countries. Country specific projections made by the United Nations (UN) and the US Census Bureau differ significantly in their estimates of the impact of AIDS. The UN projects that AIDS will reduce the population growth of the most severely affected countries in Africa by 13 million by 2005 and 30 million by 2025, while the US Census Bureau projects the reduction to be four times larger (59 million by 2005 and 120 million by 2025). These differences are due largely to the use of different methodologies for projecting future levels of adult HIV prevalence. Other factors contributing to the different projections are different estimates of current levels of HIV prevalence and different assumptions about the length of the incubation period (from initial infection until death from AIDS) and the perinatal transmission rate. In addition to the number of deaths caused by AIDS, useful indicators of mortality include life expectancy at birth, the under five mortality rate and the life-time risk of dying from AIDS. An equation for estimating the impact of AIDS on life expectancy is presented and its use is illustrated. CONCLUSION: It is clear that AIDS has already increased mortality significantly in many countries and will continue to do so in the coming decades. Uncertainty about current and future levels of HIV prevalence among adults leads to differences in the projections of future AIDS-related mortality. As data and projection methodologies improve, the differences in projections may be reduced for sub-Saharan Africa, but the growing epidemic in some of the largest countries of Asia may increase uncertainty about future global impacts.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Projections of auditory cortex onto the inferior colliculus in the rat.

The organization of the neocortical projection to the inferior colliculus (IC) was studied in 36 rats using retrograde transport of horseradish peroxidase (HRP) or horseradish peroxidase conjugated with lectin (WGA-HRP). Projection to the external and dorsal cortices originates in the temporal neocortical areas Te 1, Te 2 and Te 3 and in the parietal area Par 2. The corticocollicular projection is predominantly ipsilateral with a weak contralateral contribution. Projection to the rostromedial and rostrolateral part of the external cortex (EC) of the IC arises mainly from the areas Par 2 and Te 1. The participation of the cortical areas Te 2 and Te 3 in this projection is only small. The fibres to the caudobasal part of the external cortex descend from the caudal parts of areas Te 1, Te 2, and Te 3. The corticocollicular projections to the dorsal part of the IC are more numerous than the projections to the EC and originate in all temporal areas, i.e. in area Te 1, Te 2 and Te 3. However, the topographical organization of the corticocollicular projection is more pronounced in the part which projects to the EC. We suggest that the topographical organization of the projections to the EC corresponds with the map of auditory space in the EC. The source of corticocollicular fibres are exclusively neurones of lamina V of all cortical areas sending their fibres to the IC.

Animals↗
PubMed1998

Periaqueductal gray matter projection to the parabrachial nucleus in rat.

The efferent projections from the periaqueductal gray matter (PAG) to the parabrachial nucleus (PB) were studied in the rat following microinjections of the anterograde axonal tracer Phaseolus vulgaris-leucoagglutinin (PHA-L) into restricted regions of the PAG. The dorsomedial and dorsolateral PAG columns project almost exclusively to the superior lateral PB subnucleus, whereas the lateral and ventrolateral PAG columns project to five lateral PB sites: dorsal lateral subnucleus, medial and lateral crescent areas (which flank the dorsal lateral PB subnucleus), central lateral subnucleus (rostral portion), and superior lateral subnucleus. The PAG region lying near the cerebral aqueduct projects to five lateral PB sites: external lateral subnucleus (inner subdivision), medial and lateral crescent areas, central lateral subnucleus (rostral portion), and dorsal lateral subnucleus. The internal lateral PB subnucleus, which projects exclusively to the intralaminar thalamic nuclei, and the Kölliker-Fuse nucleus were not innervated by the PAG. The PAG selectively innervates individual PB subnuclei that may be part of the spino-parachio-forebrain pathway. All PAG columns, including the aqueductal region, project to the superior lateral PB subnucleus, a presumed nociceptive relay site that receives inputs from multiple spinal cord regions (laminae I, V, and VIII) and projects to the ventromedial and retrochiasmatic hypothalamic areas-two regions that have been implicated in complex goal-directed behavior (e.g., food intake and reproductive function). Earlier studies demonstrated that the dorsal lateral and external lateral PB subnuclei (inner division) receive overlapping inputs from the superficial dorsal horn (laminae I and II) and the nucleus tractus solitarius, and both PB subnuclei send projections to limbic forebrain areas (e.g., hypothalamus, preoptic region, amygdala). Because the PAG projects to both of these PB subnuclei, this projection system possibly functions as a behavioral state-dependent filter system that modulates ascending nociceptive and/or visceral information as it is relayed through the PB to forebrain sites.

Amygdala↗
PubMed2002

Project IMPACT: results from a pilot validity study of a new observational database.

OBJECTIVE: The objective of this study was to evaluate the accuracy of the information contained in the Project IMPACT database. Project IMPACT is a comprehensive database system developed to measure and describe the care of intensive care patients. This database is being used by a large group of hospitals to help clinicians improve the care of these patients. Data on patient demographics, diagnoses, treatment, and outcomes are entered into the Project IMPACT database by staff at participating hospitals. This pilot study was a first step in assessing the accuracy of these data to determine the usefulness of the Project IMPACT database for measuring intensive care unit (ICU) performance and patient outcomes. DESIGN: The design of the pilot study was the independent abstraction of selected data items from a random sample of ICU patient records from two hospitals participating in Project IMPACT. The abstracted data were compared with the data existing in the Project IMPACT database for agreement. SETTING: Abstraction was performed onsite at the two pilot hospitals by a trained abstractor who was not affiliated with either hospital. PATIENTS: Patients whose records were abstracted included 45 randomly selected ICU patients at each of the two pilot hospitals. MEASUREMENTS AND MAIN RESULTS: Comparison of the Project IMPACT data with the independently abstracted data indicated good agreement (80% or above) on discrete items, such as type of ICU patient. Poorer agreement (under 80%) was seen for continuous items (e.g., 24-hr urine output) and coded items requiring judgment (e.g., reason for ICU admission). CONCLUSIONS: The pilot study showed good internal validity for most of the abstracted variables. High agreement rates were observed, regardless of method of original data capture (electronic download or manual entry), although agreement was higher for some data items that had been electronically downloaded into the Project IMPACT database. The results suggest that Project IMPACT is a valuable resource for ICUs to collect and evaluate information about treatment and patient outcomes.

Database Management Systems↗
PubMed2003

Working together: supporting projects through action learning.

Recent years have seen tremendous growth in knowledge management projects within the NHS. Project staff must acquire rapidly a wide range of task-related skills. Conventional training courses may be inappropriately timed or unavailable to project staff. Action learning provides a group-based means of meeting skills deficits associated with project management and delivery. This paper describes an action learning set for project staff on five knowledge management projects within Trent Region. A brief evaluation aimed to identify most and least useful and most and least enjoyable features of the action learning set. Comments on the facilitation and the content of the action learning sessions are analysed. Action learning is feasible in meeting the training needs of project staff. It may also provide a means of meeting the shared learning needs of communities of practice within a virtual environment. Knowledge management does not merely involve management and delivery within innovative projects but also requires exploiting shared learning across projects.

Cooperative Behavior↗
PubMed2003

Why good projects fail anyway.

Big projects fail at an astonishing rate--more than half the time, by some estimates. It's not hard to understand why. Complicated long-term projects are customarily developed by a series of teams working along parallel tracks. If managers fail to anticipate everything that might fall through the cracks, those tracks will not converge successfully at the end to reach the goal. Take a companywide CRM project. Traditionally, one team might analyze customers, another select the software, a third develop training programs, and so forth. When the project's finally complete, though, it may turn out that the salespeople won't enter in the requisite data because they don't understand why they need to. This very problem has, in fact, derailed many CRM programs at major organizations. There is a way to uncover unanticipated problems while the project is still in development. The key is to inject into the overall plan a series of miniprojects, or "rapid-results initiatives," which each have as their goal a miniature version of the overall goal. In the CRM project, a single team might be charged with increasing the revenues of one sales group in one region by 25% within four months. To reach that goal, team members would have to draw on the work of all the parallel teams. But in just four months, they would discover the salespeople's resistance and probably other unforeseen issues, such as, perhaps, the need to divvy up commissions for joint-selling efforts. The World Bank has used rapid-results initiatives to great effect to keep a sweeping 16-year project on track and deliver visible results years ahead of schedule. In taking an in-depth look at this project, and others, the authors show why this approach is so effective and how the initiatives are managed in conjunction with more traditional project activities.

Efficiency, Organizational↗
PubMed1996

Organization of afferent and efferent projections of the nucleus basalis prosencephali in a passerine, Taeniopygia guttata.

The connections of nucleus basalis (NB) of the rostral forebrain of the zebra finch were investigated electrophysiologically and with anterograde and retrograde tracing methods to determine their functional organization, the sources of their pontine afferents, and the targets of their telencephalic efferents. The nucleus was found to be partitioned into three major components, a rostral lingual part that received a hypoglossal projection via a lateral subnucleus of the principal sensory trigeminal nucleus (PrV), a middle beak part that received a trigeminal projection via a medial subnucleus of PrV, and a caudal auditory part that received a short latency auditory projection via the intermediate nucleus of the lateral lemniscus. Beak NB also received a projection from a paralateral lemniscal nucleus, and the dorsocaudal part of auditory NB and the medially adjacent neostriatum also received a projection from a lateral subnucleus of the superior vestibular nucleus (VS). The efferent projections of each of the three major parts of NB were mainly to the adjacent neostriatum frontale (NF), which then provided projections to the lobus parolfactorius (exclusive of area X), the lateral archistriatum intermedium (Ail), and the lateral neostriatum caudale (NCl). Ail received a projection from NCl and provided terminal fields to the contralateral NCl and the NF. The major projections of Ail, however, descended bilaterally through the brainstem via the occipitomesencephalic tracts, with dense terminations in the medial spiriform nucleus and with extensive bilateral terminations throughout the lateral reticular formation of the pons and medulla. For the most part, jaw, tongue, and tracheosyringeal motor nuclei did not receive terminations. The results suggest that NB in zebra finch, like NB in pigeon and duck, is likely to be a major component of trigeminal sensorimotor circuitry involved in feeding and in other oral-manipulative behaviors. Results also show that the auditory component of NB is not directly linked to the vocal control system at telencephalic levels, but the possibility remains that the lingual, beak, and auditory parts of NB play a role in vocalization by multisynaptic influences on cranial nerve motor nuclei innervating various parts of the vocal tract.

Afferent Pathways↗
PubMed1997

Development of differential preganglionic projections to pre- and paravertebral sympathetic ganglia.

Sympathetic preganglionic axons project to spatially distinct targets in the periphery. A precise topographic pattern exists within the thoracic preganglionic cell column relative to the direction of axonal projections within the sympathetic chain. In this study, the time course and pattern of axonal outgrowth from different populations of preganglionic neurons in the chicken embryo is examined in detail to clarify the origin of the topography in this system. Projections to prevertebral targets are established by development of the splanchnic nerves by stage 25, well after the earliest somatic motor projections at stage 19 but at least two stages before the reported onset of paravertebral projections. Further, preganglionic axons that project rostrally into the sympathetic chain may do so earlier than those that project caudally in the chain. The separation of preganglionic axons into prevertebral, rostral paravertebral or caudal paravertebral directions occurs at a common site in the ventral mesenchyme, established by the initial ventromedial projection of the splanchnic nerves. Analysis of the axonal trajectories of rostrally and caudally projecting cells reveals that preganglionic axons are not selectively fasciculated before their point of separation at the sympathetic chain. The patterning of the preganglionic cell column is specified before the establishment of functional connections within the chain, indicating that target contact is not a determinant of the segmental pattern. We suggest that the differential outgrowth of preganglionic axons to peripheral targets is determined by the unique identities of underlying subpopulations of preganglionic axons.

Acetylcholinesterase↗
PubMed1997

Organization of efferent projections from the parabrachial area to the hypothalamus: a Phaseolus vulgaris-leucoagglutinin study in the rat.

The organization of projections from the parabrachial (PB) area to the hypothalamus was studied in the rat by using microinjections of Phaseolus vulgaris-leucoagglutinin (PHA-L) into subregions of the PB area. The present study is a follow-up of two former studies (Bernard et al. [1993] J. Comp. Neurol. 329:201-229; Aldén et al. [1994] J. Comp. Neurol. 341:289-314) that examined PB projections onto the amygdala and the bed nucleus of the stria terminalis. The results demonstrate that 1) the mesencephalic PB region, centered in the lateral portion of the superior lateral subnucleus projects extremely densely to almost the entire dorsomedial subdivision of the ipsilateral ventromedial hypothalamic nucleus; 2) the mesencephalic PB region, located in the medial portion of the superior lateral subnucleus and weakly overflowing into the rostralmost dorsal lateral pontine subnucleus, projects densely to the retrochiasmatic area and, to a lesser extent, to the ipsilateral ventromedial nucleus of the hypothalamus; 3) the PB region, including the central lateral, a portion of the superior lateral, and the outer external lateral subnuclei, projects densely to the ipsilateral median, anteroventral, and periventricular preoptic hypothalamic nuclei and projects more weakly to the dorsal border of the paraventricular nucleus (PVN). No consistent projection was found in the magnocellular PVN. All of these PB regions also project diffusely to the dorsomedial area and to a small tuberal subfornical hypothalamic area. In addition, the medial half of the PB area projects consistently to the posterior lateral hypothalamus. It is suggested that these pathways may be involved in aversive-defensive behavior, in autonomic and neuroendocrine aspects of pain, and in feeding and energy metabolism regulation.

Amygdala↗
PubMed1997

Differential central projections of physiologically characterized horizontal semicircular canal vestibular nerve afferents in the toadfish, Opsanus tau.

Anatomical and neurophysiological studies were undertaken to examine the central projection pattern of physiologically characterized horizontal semicircular canal vestibular nerve afferents in the toadfish, Opsanus tau. The variations in individual response characteristics of vestibular nerve afferents to rotational stimulus provided a means of typing the afferents into descriptive classes; the afferents fell into a broad continuum across the spectrum from low-gain, velocity-sensitive to high-gain, acceleration-sensitive responses (Boyle and Highstein [1990b] J. Neurosci. 10:1557-1569; Boyle and Highstein [1990a] J. Neurosci. 10:1570-1582). In the present study, each afferent was typed as a low-gain, high-gain, or acceleration fiber during rotational or mechanical stimulation (Rabbitt et al. [1995] J. Neurophysiol. 73:2237-2260) and was then intracellularly injected with biocytin. The axons were reconstructed, and the morphology, synaptic boutons, and projection pattern of each axon were determined. The results indicated that the three descriptive classes of vestibular nerve afferents have unique as well as overlapping central projection patterns and destinations in the vestibular nuclei, with intranuclear parcellation in the anterior octavus, magnocellularis, tangentialis, posterior octavus, and descending octavus nuclei. In general, increased sensitivity and faster response dynamics were correlated with both a more extensive central projection and a progressive increase in morphological complexity. Low-gain, velocity-sensitive fibers were the simplest morphologically, with the fewest number of branches (n = 17) and shortest length (4,282 microm), and projections were confined to the middle portions of the vestibular nuclei. High-gain, velocity-sensitive fibers were morphologically more diverse than low-gain fibers, with a greater number of branches (n = 26), longer length (6,059 microm), 29% greater volume, and a more widespread projection pattern with projections to both the anterior and the middle portions of the vestibular nuclei. Acceleration fibers were morphologically distinct from low- and high-gain fibers, with more elaborate branching (n = 41), greatest overall length (17,370 microm) and volume (16% greater than high gains), and displayed the most extensive central projection pattern, innervating all vestibular nuclei except tangentialis. Thus, there are anatomically demonstrable differential central projections of canal afferents with different response dynamics within the vestibular complex of the fish.

Animals↗