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S B Edwards

Publications and source records attributed to S B Edwards.

14 recordsLinked to original sources
PubMed1979

Sources of subcortical projections to the superior colliculus in the cat.

A comprehensive search for subcortical projections to the cat superior colliculus was conducted using the retrograde horseradish peroxidase (HRP) method. Over 40 different subcortical structures project to the superior colliculus. The more notable among these are grouped under the following categories. Visual structures: ventral lateral geniculate nucleus, parabigeminal nucleus, pretectal area (nucleus of the optic tract, posterior pretectal nucleus, nuclei of the posterior commissure). Auditory structures: inferior colliculus (external and pericentral nuclei), dorsomedial periolivary nucleus, nuclei of the trapezoid body, ventral nucleus of the lateral lemniscus. Somatosensory structures: sensory trigeminal complex (all divisions, but mainly the gamma division of nucleus oralis), dorsal column nuclei (mostly cuneate nucleus), and the lateral cervical nucleus. Catecholamine nuclei: locus coeruleus, raphe dorsalis, and the parabrachial nuclei. Cerebellum: medial, interposed, and lateral nuclei, and the perihypoglossal nuclei. Reticular areas: zona incerta, substantia nigra, midbrain tegmentum, nucleus paragigantocellularis lateralis, and the hypothalamus. Evidence is presented that only the parabigeminal nucleus, the nucleus of the optic tract, and the posterior pretectal nucleus project to the superficial collicular layers (striatum griseum superficiale and stratum opticum), while all other afferents terminate in the deeper layers of the colliculus. Also presented is information concerning the rostrocaudal distribution of some of these afferent connections. These findings stress the multiplicity and diversity of inputs to the deeper collicular layers, and more specifically, identify multiple sources of the physiologically well-known representations of the somatic and auditory modalities in the colliculus.

Animals↗
PubMed1979

Corticotectal and other corticofugal projections in neonatal cat.

Adult physiological properties of cat superior colliculus cells develop gradually during the first two months of life. Since many of the neuronal properties in the adult cat appear to depend upon the integrity of visual cortex, it was postulated that the maturation of superior colliculus cells is, in large part, a reflection of corticotectal maturation. An attempt was made to study the development of the corticotectal pathway with the autoradiographic tracing technique. Injections of [3H]leucine were made in the visual cortex of kittens 6 h to 12 days of age and animals were sacrificed 20-24 h later. A dense projection from visual cortex to the superior colliculus and to the lateral geniculate nucleus was noted in all animals. Both projections appeared to be topographically organized. In addition, cortical projections to the lateral posterior-pulvinar region and sparse projections to the contralateral visual cortex were noted. Two, non-mutually exclusive, explanations for the presence of a corticotectal pathway in the absence of mature cell properties in the superior colliculus are most apparent: (a) corticotectal synapses are incompletely formed at birth and require many weeks to develop, and (b) corticotectal cells are immature during early postnatal life and cannot impress adult-like characteristics upon the superior colliculus cells until they, themselves, 'mature'.

Age Factors↗
PubMed1979

The force-interval relationship of the left ventricle.

We have carried out a quantitative analysis of the force-interval relationship of the human left ventricle and compared it to previous studies done in both intact subjects as well as isolated muscle. The characteristics of the force-interval relationship of the normal patient resembed those of normal isolated mammalian muscle (except when exposed to high levels of catecholamines). The relationship in group 2 (patients with increased left ventricular dimensions and normal pressure indices) resembled those obtained from isolated muscles from hypertrophied hearts. The relationship from group 3 (patients with increased left ventricular EDDs and depressed pressure indices, two of whom were in clinical heart failure) resumbled those induced in normal muscles exposed to high levels of catecholamines, and those obtained from experimentally induced heart failure. The force-interval relationships of the four patients who fell into the third group were strikingly different from the other groups. This suggests that the force-interval relationship may be useful to describe changes in the inotropic state of the patient's heart.

Adolescent↗
PubMed1978

The superior colliculus control of pinna movements in the cat: possible anatomical connections.

Possible anatomical pathways mediating superior colliculus control of pinna movements were determined in the cat using the orthograde autoradiographic tracing method and the retrograde horseradish peroxidase technique. This was done in the following manner. First, the division of the facial nucleus that innervates the pinna muscles was determined by injecting the pinna muscles with HRP and surveying the facial nucleus for retrogradely filled cells. Second, the brainstem regions that project the facial nucleus were identified using the horseradish peroxidase method. Third, the superior colliculus projections to these areas were studied using the autoradiographic tracing method. The results suggest that superior colliculus control of pinna movements is mediated entirely by indirect connections with the facial nucleus and that these connections occur mainly in a paralemniscal zone in the lateral midbrain. Of all the brainstem regions shown by the horseradish peroxidase experiments to project to the facial nucleus only this midbrain paralemniscal zone received a projection from the superior colliculus that was dense and overlapped precisely the region containing facial projecting neurons. Further autoradiographic tracing revealed that the facial nucleus was the primary brainstem target of this paralemniscal zone and that all paralemniscal fibers projecting to the facial nucleus ended in the subdivision that innervates the pinna muscles. Other paralemniscal efferents terminate in the opposite paralemniscal zone. The data suggest that other connections between the superior colliculus and the facial nucleus may occur in the cuneiform nucleus of the midbrain, the region around the oculomotor complex, and the reticular formation dorsal to the superior olive.

Animals↗
PubMed1978

Superior colliculus connections with the extraocular motor nuclei in the cat.

Direct and indirect projections from the cat superior colliculus to the extraocular motor nuclei were studied using the orthograde autoradiographic tracing method, the retrograde horseradish peroxidase technique, and Golgi methods. The results show that the superior colliculus projects to the central gray matter directly overlying the oculomotor complex. This projection arises almost entirely from the rostral third of the colliculus, and it terminates most heavily over the rostral half of the oculomotor complex. Dendrites of oculomotor cells extend into this tectal termination zone, making direct tecto-oculomotor contacts possible. Central gray cells within this termination zone project bilaterally to the abducens nuclei. It is proposed that the superior colliculus projection to the supraoculomotor central gray matter and the projection from the central gray matter to the abducens nuclei play a role in convergent eye movements. The superior colliculus projects lightly to a cell group directly ventrolateral to the trochlear nucleus. The superior colliculus sends a small direct projection to the contralateral abducens nucleus and a substantial projection to wide regions of the reticular formation that have been shown previously to project, in turn, to the abducens nucleus. Colliculus cells projecting to the abducens nucleus and adjacent reticular formation are located only in the caudal three-fourths of the colliculus, where they become increasingly concentrated at successively more caudal levels. It is proposed that the graded density of the cells of origin of this projection is the basic structural mechanism by which the colliculus generates horizontal foveating saccades of different amplitudes. Laminar analysis of the origin of all the superior colliculus projections to the extraocular motor regions described here revealed that they arise mostly from the stratum griseum intermedium.

Abducens Nerve↗
PubMed1978

Ventricular tachyarrhythmia due to cardiac sarcoidosis in a child.

Cardiac involvement by systemic sarcoidosis is well known, but occurs rarely. It usually manifests as either heart block, heart failure due to direct myocardial involvement, or cor pulmonale. We present the case of a patient with cardiac sarcoidosis who had ventricular tachycardia and congestive heart failure. Although there was other organ system involvement, the cardiac manifestation was the first to become clinically apparent. Therapy consisted of quinidine sulfate to control the arrhythmias and chronic diuretic therapy to control congestive heart failure. Steroid therapy was initially associated with recurrence of the ventricular tachycardia and was discontinued. It was reinstituted 18 months later when other organ system involvement developed with no recurrence of the ventricular tachyarrhythmia. The patient responded well to therapy and is currently doing well. This case is presented to illustrate a somewhat unusual, but nevertheless important, etiology of ventricular tachyarrhythmias. The recognition of underlying sarcoidosis is critical because of the propensity for other organ system involvement by this disease process.

Cardiomyopathies↗
PubMed1977

The commissural projection of the superior colliculus in the cat.

The origin, course, and termination of the commissural projection of the superior colliculus were studied using the orthograde and autoradiographic tracing method and the retrograde method utilizing horseradish peroxidase. The complementary and mutually confirming sets of data showed that the commissural fibers interconnect a restricted region of the colliculi. This region includes the strata grisea intermedium and profundum and to a lesser degree the stratum opticum. It extends throughout only the rostral part of the colliculus where it ends abruptly at a level slightly less than half the distance from the anterior border of the deep gray layers. By using the needle used for isotope injection to record multiunit responses to somatic and visual stimuli, direct evidence was obtained that this region falls within that functional area of the colliculus devoted to face representation and central vision. The results also suggested that more commissural fibers arise from lateral than medial parts of this region and that many fibers interconnect corresponding points in the colliculi. In addition to intertectal connections, the commissural projection contains decussating axons which terminate in tegmental structures and within a restricted zone of the central gray matter directly overlying the oculomotor complex. The results are discussed in relation to the possible role the commissural projection plays in the regulation of eye and head movement.

Animals↗
PubMed1975

Autoradiographic studies of the projections of the midbrain reticular formation: descending projections of nucleus cuneiformis.

The descending projections of nucleus cuneiformis in the cat were traced by autoradiography in the transverse and sagittal planes following stereotaxically placed injections of 3H-leucine. Many descending axons are organized into distinct fiber systems, of which the largest and most well-defined crosses directly in the midbrain and descends through the ventromedial tegmentum of the brain stem. This fiber system first terminates profusely in n. reticularis tegmenti pontis and then proceeds through the rhombencephalic tegmentum emitting transversely oriented branches to n. reticularis pontis caudalis and gigantocellularis, the raphe magnus and the facial nucleus...

Animals↗