Ventral Lamella Research Articles

Morphology of the inferior olivary complex of the rhesus monkey (Macaca mulatta).

AbstractThe morphology of the inferior olivary complex was determined in the rhesus monkey (Macaca mulatta). The position, configuration, and relations of each of its components were ascertained in serial transverse sections extending from caudal through rostral poles of the complex. The medial accessory nucleus was divided into seven cell groups (labeled a through g). The principal nucleus consisted of well‐developed dorsal, ventral, and lateral lamellae and a criterion was established for distinguishing the boundaries of each. This distinction was based upon the pattern of invagination that developed in the principal nucleus in progressing rostrally from its caudal pole. The dorsal and lateral lamellae each presented a characteristic pattern of major invaginations, while the ventral lamella did not. Finally, a detailed comparison was made of the inferior olivary complex of the monkey with that of the cat as determined by other investigators. It was shown that the medial and dorsal accessory nuclei of the two species appeared similar and that the major difference between these species concerns the principal nucleus.

Topical projection of the olivocerebellar system in the cat: an electrophysiological study.

AbstractUsing electrophysiological recording, topical aspects of the olivocerebellar projection were studied in the locally anesthetized cat immobilized with Flaxedil. Transcortical evoked potentials were recorded simultaneously from eight electrodes distributed over the cerebellar surface, and averaged with a LINC computer. Precautions were taken to eliminate virtual potentials from this volume conductor situation. The evoked potentials consisted of a 4–6 msec positive spike, latency 4.5–7 msec, followed by a 15–30 msec slow negative deflection. Each was recorded from one or two folia contralateral in distribution. Medial and dorsal accessory nuclei project largely to cerebellar vermis. A rostrocaudal relationship was found between posterior vermis and medial accessory nucleus, and vermal anterior lobe received its projection from the caudal and midportions of medial and dorsal accessory components. A dense representation of accessory nucleus responses was present over the declive as compared with other cerebellar areas. Paravermal responses of anterior lobe derived from rostral dorsal accessory olive, and principal olive connected to the hemispheral region. The ventral lamella of principal olive projected to Crus II, dorsal lamella to Crus I. These lobules are represented rostrally in the principal nucleus, whereas the source for paramedial lobules was situated more caudally. The results correlate well with the retrograde degeneration studies of Brodal ('40, '54) but differ in the detail of some projections.

Demonstration of a somatotopical pattern in the cortico-olivary projection in the cat. An experimental-anatomical study.

Following small lesions of the first sensorimotor (MSI) and second somatosensory (SII) cortical areas the ensuing degeneration in the inferior olives was studied with the Nauta method in 14 cats. No convincing signs of degeneration were found in the olives in cases with lesions restricted to the first and second somatosensory areas (SI and SII). Following lesions of the primary “motor” cortex (anterior sigmoid gyrus and rostral part of the coronal gyrus) degeneration was consistently found in the olive of both sides. The contralateral projection is somewhat more abundant than the ipsilateral, but both are modest. Degeneration is restricted to certain parts of the olivary complex (see Fig. 11). Lesions restricted to different somatotopical subdivisions of the primary “motor” cortex give rise to degeneration distributed in a somatotopical pattern in certain areas of the medial and dorsal accessory olives and the rostral part of the ventral lamella. Somatotopical patterns could not be established in the smaller projections to some other minor olivary regions. When the findings are correlated with the pattern of the olivocerebellar projection it can be concluded that there is a somatotopically organized direct corticoolivo-cerebellar pathway to the intermediate part of the anterior lobe, the posterior vermis and the crus II. Attempts to correlate the findings with physiological observations are difficult. It appears that the current view that climbing fibres arise only in the olive may need revision. The role of the pontine nuclei in mediating somatotopically localized cerebellocerebellar impulses appears to have been underestimated.

Responses in the inferior olive to stimulation of the cerebellar and cerebral cortices in the cat

1. Extracellular field potentials and single unit responses have been recorded from the inferior olive of the cat following stimulation of the surface of the contralateral paramedian lobule of the cerebellum, and of the ipsilateral cerebral cortex. 2. Cerebellar stimulation results in antidromic invasion of inferior olivary neurones via the climbing fibres. These responses are followed by synaptic discharges which may be generated through climbing fibre recurrent collaterals. 3. Precise histological controls have shown that these responses to stimulation of the paramedian lobule are located in the ventral lamella of the principal olive. 4. Unifocal stimulation of the sensori-motor cortex with surface-anodal pulses evokes synaptically generated discharges of neurones in the central lamella, with a latency of 8-9 msec. The area of cortex yielding responses has been mapped at chosen stimulus intensities and the limitations of the maps have been discussed. 5. It has been shown that the initial excitatory responses obtained from either cortex are followed by an inhibition which lasts about 100 msec, and gives way to a period of recovery or facilitation. This, in turn, is succeeded by a further period of inhibition. Possible neural substrates for these changes have been discussed.

Lestodiplosis alvei sp.n. (Diptera, Cecidomyidae)

Male. Length about 1·5 mm. Antennae slightly longer than head, thorax and abdomen: 2 + 12, basal enlargement of flagellar segments with regular ring of moderately long stout setae and one ring of circumfila, distal enlargement with two rings of circumfila and irregular ring of stout setae, loops of circumfila regular and moderately long, those on basal enlargement extending about one-third length of stem, distal ring on distal enlargement extending about two-thirds length of neck; 1st and 2nd flagellar segments fused; 3rd flagellar segment with stem about three times as long as broad, neck slightly longer, about three-and-a-half times as long as broad, distal end slightly darkened as on all flagellar segments; 10th flagellar segment with stem about four times as long as broad, neck slightly longer in proportion. Palpi quadriarticulate with few setae: proximal segment quadrate, 2nd just over three times as long as broad, 3rd about three times as long as broad, the same width as 2nd, distal segment about four times as long as broad, slightly narrower than two previous segments. Thorax brown. Wings hyaline; 3rd vein reaching margin at apex of wing. Legs hairy; claws moderately curved, simple; empodium slightly shorter than claws. Genitalia: basal clasp segment long narrow, small basal lobe prominent; distal clasp segment long narrow, darkened; dorsal lamella moderate length and breadth, distinctly longer than ventral lamella, deeply emarginate, each lobe rounded; ventral lamella comparatively short but broad; style long, moderately stout.