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J M Wild

Publications and source records attributed to J M Wild.

At least 73 records · Page 4Linked to original sources
PubMed1997

Normalisation of metabolite images in 1H NMR spectroscopic imaging.

Single slice proton magnetic resonance spectroscopic images were taken from a volume of interest (VOI), which was localised using the point resolved spectroscopy (PRESS) sequence. Non-uniformities in the excitation profile of the VOI within the image plane were accounted for using a uniformity correction image. Metabolite images were divided on a voxel-by-voxel basis with a water image obtained from a VOI of the same spatial dimensions from a phantom acquisition. Normalisation procedures carried out on phantom metabolite images were needed to account for the spatial shift in the excitation profile of the VOI, which varies linearly with the chemical shift of the metabolite. Patient metabolite images were then normalised using a VOI water image from a phantom acquisition, which was spatially shifted according to the metabolite chemical shift. In a study of 14 stroke patients, metabolite maps of the distribution of choline, creatine and N-acetyl aspartate (NAA) were constructed. The spectral signal intensities from these metabolites in the infarcted and in the contralateral region were calculated using the raw maps and secondly with the same maps after the B1 normalisation process. In the initial analysis only the metabolite NAA showed a significant decrease, whilst all three metabolites showed a significant reduction in the normalised analysis. These results confirm that normalisation of PRESS localised images does have a significant bearing upon any quantitative measurements made using such images.

Algorithms↗
PubMed1997

Functional anatomy of neural pathways contributing to the control of song production in birds.

In birds, as in humans, vocal control involves the intricate coordination of three major groups of muscles, namely, those of the vocal organ, the respiratory apparatus, and the vocal tract, including the jaw and tongue. The neural pathways involved in the control of each of these groups of muscles are described for songbirds and compared with those in non-oscine birds and mammals. The pathway in songbirds that controls the syrinx, the bird's vocal organ, originates in the telencephalon and projects via the occipito-mesencephalic tract directly upon vocal motoneurons in the medulla. Activity in this pathway configures the syrinx into phonatory positions for the production of species typical vocalizations. Another component of this pathway mediates control of respiration during vocalization, since it projects upon both expiratory and inspiratory groups of premotor neurons in the ventrolateral medulla, as well as upon several other nuclei en route. This pathway appears to be primarily involved with the control of the temporal pattern of song, but is also importantly involved in the control of vocal intensity, mediated via air sac pressure. There are extensive interconnections between the vocal and respiratory pathways, especially at brainstem levels, and it may be these that ensure the necessary temporal coordination of syringeal and respiratory activity. The pathway mediating control of the jaw appears to be different from those mediating control of the syrinx and respiratory muscles. It originates in a different part of the telencephalon and projects upon premotor neurons in the medulla that, on preliminary analysis, appear to be separate from those projecting upon the syringeal motor nucleus. The separateness of this pathway may reflect the imperfect correlation of jaw movements with the dynamic and acoustic features of song. The brainstem pathways mediating control of vocalization and respiration in songbirds have distinct similarities to those in non-oscine birds and in mammals such as cats and monkeys. However, songbirds and parrots, like humans, but unlike other non-songbirds, have developed a special telencephalic vocal control system for the production of learned vocalizations.

Animals↗
PubMed1997

Localization of androgen receptor mRNA-containing cells in avian respiratory-vocal nuclei: an in situ hybridization study.

Song development and song pattern formation in oscine songbirds are influenced by steroid hormones such as estrogens and androgens, and the control of vocal pattern generation is mediated via a network of interconnected vocal and respiratory nuclei. The main components of the respiratory part of the network are the expiratory and inspiratory premotor nuclei, known as retroambigualis (RAm) and the rostral ventral respiratory group (rVRG), respectively. These respiratory components play an integral role in song production either by providing the expiratory pulses of air required for each and every song syllable, or by controlling inspiration between syllables in the form of minibreaths, and between phrases for major replenishments of air. Here we analyze the distribution of androgen receptors (AR) and estrogen receptors (ER) in the midbrain and hindbrain of male and female zebra finches, and male canaries and green finches, using in situ hybridization with cRNA probes of the zebra finch AR and ER. ERmRNA was not expressed in any of the respiratory-vocal nuclei of the midbrain or hindbrain, but ARmRNA was expressed in the tracheosyringeal motor nucleus (nXIIts) and in RAm and rVRG. The size of the ARmRNA defined RAm and rVRG was similar in male and female zebra finches, but the size of ARmRNA defined nXIIts was slightly sexual dimorphic. Previously undescribed areas of ARmRNA expression outside the respiratory-vocal network in the brain stem were the nucleus semilunaris and layers 10-12 of the optic tectum. AR-mRNA expression in the respiratory-vocal nuclei of adult male songbirds, adult female zebra finches, and juvenile zebra finches suggests that the temporal pattern of learned and unlearned vocalizations is sensitive to androgen-dependent mechanisms mediated by RAm and rVRG.

Animals↗
PubMed1996

Central projections and somatotopic organisation of trigeminal primary afferents in pigeon (Columba livia).

Injections of cholera toxin B-chain conjugated to horseradish peroxidase into individual peripheral branches of the trigeminal nerve or into the trigeminal ganglion showed that an ascending trigeminal tract (TTA) terminated in distinct ventral and dorsal divisions of the principal sensory nucleus (PrVv and PrVd, respectively), and a descending tract (TTD) terminated within pars oralis, pars interpolaris, and pars caudalis divisions of the nucleus of TTD (nTTD) and within the dorsal horn of the first six cervical spinal segments. In PrVd, mandibular, ophthalmic, and maxillary projections were predominantly located dorsally, ventrally, and medially, respectively. In nTTD, mandibular projections lay dorsomedially, ophthalmic projections lay ventrolaterally, and maxillary projections lay in between. At caudal medullary and spinal levels, mandibular projections were situated medially, ophthalmic projections were situated laterally, and maxillary projections were situated centrally. The terminations within the dorsal horn were most dense in laminae III and IV and were least dense in lamina II, with laminae III-IV also receiving topographically organised contralateral projections. Extratrigeminal projections were mainly to the external cuneate nucleus by way of a lateral descending trigeminal tract (lTTD; Dubbeldam and Karten [1978] J. Comp. Neurol. 180:661-678) and to the region of the tract of Lissauer and lamina I of the dorsal horn. Other projections were to a region medial to the apex of pars interpolaris, to the nuclei ventrolateralis anterior (Vla) and presulcalis anterior (Pas) of the solitary complex, and sparsely to the lateral reticular formation (plexus of Horsley) ventral to TTD. No projections were seen to the trigeminal motor nuclei or to the cerebellum.

Afferent Pathways↗
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↗
PubMed1996

Baseline alterations in blue-on-yellow normal perimetric sensitivity.

BACKGROUND: the extent of any learning and fatigue effects in blue-on-yellow (B-Y) perimetry is unknown. The within- and between-eye changes in B-Y normal sensitivity at a single visit and between visits was investigated as a function of previous experience in white-on-white (W-W) perimetry and of subject age. METHODS: Sixty-one normal subjects 22 young (range 20-34 years) and 39 elderly (range 51-80 years)-- assigned to one of four groups based upon perimetric experience and age underwent B-Y perimetry on four separate occasions using Program 30-2 of a modified Humphrey Field Analyser 640. Perimetry was performed for both eyes on three consecutive days and again one week later. Global, hemifield and annular mean sensitivities and global short-term fluctuation were calculated for each eye at each visit. RESULTS: Mean sensitivity was higher in the first eye examined and increased over the 3 days. The increase in mean sensitivity was similar for each eye and was independent of perimetric experience and age. Short-term fluctuation decreased over the 3 days, regardless of eye and experience, but was more pronounced for the younger age group. The extent of all improvements varied considerably between subjects. CONCLUSIONS: Improvements in B-Y perimetric performance occurred as the familiarity with the test increased, regardless of previous W-W experience. Failure to account for such improvement could reduce the efficiency of B-Y perimetry.

Adult↗
PubMed1995

Centrifugal projections upon the retina: an anterograde tracing study in the pigeon (Columba livia).

Previous work has shown that the avian retina receives two types of centrifugal fibers from the brain. These types can be distinguished based on the size and the morphology of their terminal endings and have been termed convergent and divergent. The centrifugal fibers arise from the isthmooptic nucleus (ION) and the surrounding ectopic cell region (ECR). We used injections of anterograde tracers either to the ION/ECR or to the ECR only to determine the morphology, depth of termination, and regional distribution of the centrifugal fibers arising from each. We found that the ECR gives rise only to the divergent type of the centrifugal fiber, whereas the ION gives rise mainly to the convergent type but may also send some fibers of the divergent type. Most of the fibers project contralaterally, although a few from the ECR project ipsilaterally. The terminals of either type are not uniformly distributed throughout the retina; instead, they are found mainly in the inferior, midtemporal, to nasal portion of the retina and appear to avoid the fovea and most of the red field. By comparison, the ION receives a major projection from portions of the tectum that receive input from the fovea and the red field in a type of neural loop. The neural loop does not project to the same point (homotopic), but projects from the red field to the inferior retina (heterotopic), as was recently proposed by Holden (1990; Vis. Neurosci. 4:493-497). The distribution of centrifugal axons corresponds to displaced ganglion cells that selectively innervate the nuclei of the accessory optic system (AOS), including the nucleus of the basal optic root (dorsal, ventral, and lateral) and the nucleus lentiformis mesencephali, pars magnocellularis. We suggest that the centrifugal axons act by increasing the gain on the AOS, thereby enhancing retinal stabilization of gaze with improved accuracy of pecking of small objects.

Animals↗
PubMed1995

Convergence of somatosensory and auditory projections in the avian torus semicircularis, including the central auditory nucleus.

Projections of dorsal column, spinal, and cochlear nuclei upon the central nucleus of the torus semicircularis (otherwise known as nucleus mesencephalicus lateralis, pars dorsalis, or MLd) and upon other toral nuclei were investigated in pigeon by anterograde and retrograde tracing and electrophysiological methods. The anatomical results showed that caudal regions of the dorsal column nuclei and medial lamina V of the upper four cervical spinal segments have extensive projections upon the contralateral central auditory nucleus and upon other nuclei of the torus, in particular the core portion of the preisthmic superficial area of Puelles et al. (L. Puelles, C. Rrobles, M. Martiez-de-la-Torre, and S. Martinez, 1994, J. Comp. Neurol. 340:98-125). The projections of nucleus angularis were found to terminate throughout most of the contralateral central nucleus except the dorsomedial portion at rostral levels, where the majority of the projections of nucleus laminaris were concentrated. Nucleus angularis (and to a lesser extent nucleus laminaris) was also found to have substantial projections to certain noncentral toral nuclei, in particular to the caudomedial shell nucleus of Puelles et al. (1994). As shown positively with both Nissl and cytochrome oxidase staining and negatively with substance P labeling, this nucleus is a medial extension of more caudal regions of the central nucleus, and it is suggested that it should be included as part of the auditory midbrain. The electrophysiological results confirmed the anatomical findings by showing that evoked potentials and multiunit activity can be recorded throughout the central and noncentral toral nuclei by using electrical stimulation of the radial nerve and auditory click stimuli. The core portion of the preisthmic superficial area, however, can be regarded as a distinct somatosensory nucleus of the midbrain. It is concluded that there is substantial convergence of somatosensory and auditory inputs within both central auditory and noncentral nuclei of the torus semicircularis in pigeon.

Animals↗
PubMed1995

Organization of the avian "corticostriatal" projection system: a retrograde and anterograde pathway tracing study in pigeons.

Birds have well-developed basal ganglia within the telencephalon, including a striatum consisting of the medially located lobus parolfactorius (LPO) and the laterally located paleostriatum augmentatum (PA). Relatively little is known, however, about the extent and organization of the telencephalic "cortical" input to the avian basal ganglia (i.e., the avian "corticostriatal" projection system). Using retrograde and anterograde neuroanatomical pathway tracers to address this issue, we found that a large continuous expanse of the outer pallium projects to the striatum of the basal ganglia in pigeons. This expanse includes the Wulst and archistriatum as well as the entire outer rind of the pallium intervening between Wulst and archistriatum, termed by us the pallium externum (PE). In addition, the caudolateral neostriatum (NCL), pyriform cortex, and hippocampal complex also give rise to striatal projections in pigeon. A restricted number of these pallial regions (such as the "limbic" NCL, pyriform cortex, and ventral/caudal parts of the archistriatum) project to such ventral striatal structures as the olfactory tubercle (TO), nucleus accumbens (Ac), and bed nucleus of the stria terminalis (BNST). Such "limbic" pallial areas also project to medialmost LPO and lateralmost PA, while the hyperstriatum accessorium portion of the Wulst, the PE, and the dorsal parts of the archistriatum were found to project primarily to the remainder of LPO (the lateral two-thirds) and PA (the medial four-fifths). The available evidence indicates that the diverse pallial regions projecting to the striatum in birds, as in mammals, are parts of higher order sensory or motor systems. The extensive corticostriatal system in both birds and mammals appears to include two types of pallial neurons: 1) those that project to both striatum and brainstem (i.e., those in the Wulst and the archistriatum) and 2) those that project to striatum but not to brainstem (i.e., those in the PE). The lack of extensive corticostriatal projections from either type of neuron in anamniotes suggests that the anamniote-amniote evolutionary transition was marked by the emergence of the corticostriatal projection system as a prominent source of sensory and motor information for the striatum, possibly facilitating the role of the basal ganglia in movement control.

Animals↗
PubMed1995

The attenuation of blue-on-yellow perimetry by the macular pigment.

PURPOSE: To determine the influence of macular pigment absorption on blue-on-yellow perimetry using a technique suitable for application with the Humphrey Field Analyzer. METHODS: The sample comprised one eye from each of 46 healthy subjects (age range, 20-80 years). Macular pigment absorption was assessed by measuring medium-wavelength sensitive cone sensitivity for 460- and 570-nm narrowband stimuli at the fovea, at 5.5 degrees and at 8 degrees eccentricity. The differences in sensitivities recorded between the fovea and 8 degrees eccentricity and between 5.5 degrees and 8 degrees eccentricity for the 460-nm stimulus relative to a value of zero at 570 nm were attributed to absorption by the macular pigment. Blue-on-yellow perimetry was undertaken using a 460-nm narrowband blue Goldmann size V stimulus and a yellow 330-cdm-2 background. RESULTS: Group macular pigment absorption (mean +/- standard error) was 0.40 +/- 0.03 log units foveally and 0.00 +/- 0.03 log units at 5.5 degrees eccentricity. The group mean foveal macular pigment absorption was significantly different from zero (P < 0.01). The coefficient of repeatability for the macular pigment absorption procedure (based on test-retest data for 16 subjects) was +/- 0.28 log units at the fovea and +/- 0.35 log units at 5.5 degrees eccentricity. CONCLUSION: The net effect of ocular media and macular pigment absorption relative to 460 nm was to attenuate the blue-on-yellow visual field at the fovea by approximately 0.80 log units and elsewhere by 0.40 log units.

Absorption↗
PubMed1995

The influence of age-related cataract on blue-on-yellow perimetry.

PURPOSE: The influence of cataract on the blue-on-yellow visual field is unknown. The aim of the study was to compare the effect of age-related cataract on the normal blue-on-yellow (B-Y), yellow-on-yellow (Y-Y) and white-on-white (W-W) visual field. METHODS: Forty normal subjects (age range, 60 to 81 years) randomly performed B-Y, Y-Y, and W-W perimetry using a modified Humphrey Field Analyser 640 (HFA) (Program 24-2). Twenty age-matched patients with cataract underwent the same testing paradigm. Cataract was classified using the LOCS II system. Ocular media absorption was measured with the HFA by determining the difference in scotopic sensitivity to 410-nm and 560-nm stimuli. Forward light scatter was measured by the direct compensation technique of van den Berg. Unweighted mean deviation (MD), short-term fluctuation, and corrected pattern standard derivation indices were calculated for each patient with cataract for each of the three stimulus combinations. RESULTS: Cataract produced an adverse effect on the MD (i.e., a more negative MD) in all patients for each of the three stimulus combinations. The magnitude depended on the degree and type of cataract and was highly correlated with forward light scatter. The attenuation in sensitivity was greatest for the B-Y and W-W stimulus combinations; the B-Y field was preferentially affected by posterior subcapsular cataract and the W-W field by anterior cortical cataract. CONCLUSIONS: Cataract predominantly causes a general reduction in B-Y sensitivity. Caution therefore needs to be exercised in the interpretation of the B-Y visual field in patients in whom glaucoma and cataract coexist.

Aged↗
PubMed1995

The statistical interpretation of blue-on-yellow visual field loss.

PURPOSE: To evaluate short-wavelength-sensitive perimetry in the detection of glaucomatous field loss. METHODS: The sample consisted of 27 normal subjects, 24 patients with primary open angle glaucoma (POAG), and 27 patients with ocular hypertension (OHT). Blue-on-yellow (B-Y) and standard (W-W) perimetry was undertaken with a modified Humphrey Field Analyzer 640 on one eye of each subject and patient. The B-Y data were corrected for individual ocular media absorption. Results were compared to an age-matched normal database of 50 subjects (age range, 60 to 82 years; mean age, 70.0 years; SD, 6.4 years). Visual field indices and total and pattern deviation probability maps were calculated for both W-W and B-Y fields. RESULTS: The B-Y normal database exhibited increased between-subject variability compared to the W-W normal database (P < 0.001). The greater variability increased with the increase in eccentricity (P < 0.001) and with the increase in age (P = 0.032). All patients with POAG exhibited B-Y field loss; 11 demonstrated greater B-Y loss than the corresponding W-W field. In advanced POAG, the B-Y and the W-W fields were similar. Twenty-five of the 27 normal subjects exhibited normal B-Y fields. Five of the 27 patients with OHT manifested B-Y focal abnormality and a normal W-W field: in two, W-W focal loss subsequently developed. CONCLUSIONS: Short-wavelength-sensitive perimetry can identify visual field loss before that detected by W-W perimetry. However, the increased between-subject variability necessitates stringent statistical analysis in the definition of abnormality.

Aged↗
PubMed1994

Visual and somatosensory inputs to the avian song system via nucleus uvaeformis (Uva) and a comparison with the projections of a similar thalamic nucleus in a nonsongbird, Columba livia.

Nucleus uvaeformis (Uva), previously identified as a component of song control circuitry in songbirds, and nucleus dorsolateralis posterior thalami, pars caudalis (DLPc) in pigeon, were compared with respect to their relative positions in the dorsolateral part of the posterior thalamus, their cell types, and their afferent and efferent projections. Both nuclei are closely related to the habenulointerpeduncular tract, have similar cell types, and receive a dense projection from deep layers of the optic tectum, predominantly ipsilaterally, and a distinct projection from the dorsal column and external cuneate nuclei, predominantly contralaterally. Recordings of multiple unit activity evoked by visual and somatosensory stimuli were used to guide injections of tracer into either DLPc or Uva, and the projections to the telencephalon were charted. Both nuclei were found to have a major terminal field in the medial part of the ipsilateral neostriatum intermedium (NI), known as nucleus interfacialis (NIf) in songbirds, and a minor terminal field in the roof of the neostriatum caudale (NC). In pigeon, the DLPc terminations in NC were within a region known as neostriatum dorsale (Nd), and, in male songbirds, the Uva terminations were in the high vocal center (HVC). Recordings of visual and somatosensory evoked activity were then used to guide injections of tracer into NI, and the afferent and efferent projections were again compared in pigeon and songbirds. The projections from either DLPc or Uva were confirmed, and terminal fields were observed either in Nd in pigeon, the dorsolateral part of NC in female songbirds, or HVC in male songbirds. Injections of tracer into either Nd or HVC confirmed their sources of afferents in DLPc or Uva, respectively, and in NI, but there was incomplete overlap of the distribution of retrogradely labelled cells in NI and the terminal fields of DLPc or Uva. It is concluded that DLPc and Uva are comparable nuclei having similar afferent and efferent projections relaying visual and somatosensory information to the telencephalon. The possible role of this information in vocal control is discussed.

Animals↗
PubMed1994

The influence of induced forward light scatter on the normal blue-on-yellow perimetric profile.

The study investigated the effects of induced forward light scatter on the normal blue-on-yellow perimetric profile. Light scatter was induced using 0.00%, 0.08% and 0.16% suspensions of 500-nm-diameter polystyrene microspheres contained in optical cells. White-on-white, yellow-on-yellow and blue-on-yellow perimetry was performed using a modified Humphrey Field Analyser 640. Fifteen subjects performed perimetry with each of the scatter suspensions placed before the eye and in the cell-free situation. The degree of induced scatter for each cell was quantified using the direct compensation technique of van den Berg at small, medium and large angles of scatter. Straylight increased and perimetric sensitivity decreased with increase in scatter concentration. Forward light scatter caused a general reduction in sensitivity for all stimuli, particularly for the blue-on-yellow stimulus. This finding may have implications for the interpretation of the glaucomatous visual field in the presence of forward light scatter.

Adult↗
PubMed1994

Age-related effects of glare on luminance and color contrast sensitivity.

PURPOSE: To determine the effect of disability glare (DG) upon luminance and color contrast sensitivity for young and elderly subjects. METHODS: DG was defined as the difference in contrast sensitivity with and without the presence of a glare source. Isoluminant color gratings were modulated either along a red-green (R-G) or blue-yellow (B-Y) axis. RESULTS: Without glare the effect of age on sensitivity to both luminance and R-G color-modulated gratings was small and did not reach statistical significance (P > 0.1). However, the reduction in sensitivity for B-Y color modulation was highly significant (P < 0.01). For both age groups, DG was greatest for the R-G stimulus and least for the B-Y. DG in the elderly increased relative to the young observers for both R-G and luminance-modulated gratings (P < 0.01) but not for B-Y (P > 0.01). CONCLUSIONS: The precise effect of a glare source on color discrimination depends upon a complex interaction between the chromaticity of the glare source and that of the stimulus. In certain circumstances, such as in our R-G stimulus, glare can dramatically reduce chromatic discrimination ability by desaturating the component colors.

Adult↗
PubMed1994

Spatial summation of the differential light threshold as a function of visual field location and age.

Static differential light thresholds were measured as a function of stimulus size (Goldmann sizes I-V) along four visual field meridia (75, 165, 255 and 345 degrees) with the Humphrey Field Analyzer 640. Data were obtained for both young (n = 10, age 23.6 +/- 2.9 years) and elderly (n = 10, age 72.0 +/- 5.2 years) normal subjects. The resulting peripheral spatial summation curves could be equated to the foveal data simply by a change in size scale, which increased linearly with eccentricity. E2 values, expressing the eccentricity at which stimulus size must double for performance to remain comparable to the fovea, were in the order of 3-9 degrees. Whilst the rate of scale change is approximately the same for both young and elderly observers, differences in performance can be explained by a combination of lower sensitivity and a bias in sensitivity towards larger stimulus sizes with increasing age.

Adult↗
PubMed1994

The auditory-vocal-respiratory axis in birds.

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.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗