Shoei Sugita

The organization of neurons in the nucleus of the lateral lemniscus projecting to the superior and inferior colliculi in the rat

The topographic organization of neurons in the dorsal nucleus of the lateral lemniscus (DNLL) which project to the superior and inferior colliculi was studied using the retrograde horseradish peroxidase (HRP) and the fluorescent double labeling methods. Neurons projecting to the superior colliculus (SC) are situated in the rostral portion of the DNLL, whereas those to the inferior colliculus (IC) are found in the caudal area of this nucleus. These two portions are completely separated from each other and no neurons projecting to both the SC and the IC are observed. In the dorsolateral part of the rostral portion of the DNLL, neurons projecting to the ipsilateral SC are found, whereas neurons projecting to the contralateral SC are located in the central to medial part of the nucleus, but no neurons sending collateral axons to both sides of the SC were observed. Neurons located in the central part of the caudal area of the DNLL project to the ipsilateral IC and neurons in the lateral and medial parts project contralaterally to the IC. Some of the neurons in the caudal part of the DNLL have divergent axonal branching projecting to both sides of the IC. In the ventral nucleus of the lateral lemniscus, labeled neurons were observed only when the HRP was injected into the ipsilateral IC.

The role of uropygial gland on sexual behavior in domestic chicken Gallus gallus domesticus.

Recent studies have indicated that avian social behavior is influenced by olfactory cues. During the reproductive season a change in the chemical composition of uropygial gland secretion has been reported in some species and the hypothesis that olfactory signals may be produced by this gland has been proposed. To examine this hypothesis we performed two behavioral experiments to determine whether a females uropygial gland produces chemical signals that stimulate mating behaviors in domestic chickens. In Experiment 1 the role of the females uropygial gland in male mating behavior was examined by removing and examining the females uropygial gland. The frequency of mounts and copulations of intact male birds with sham-operated female birds was significantly higher than with uropygial glandectomized female birds. With respect to the number of waltzing that is one of the courtship displays intact males showed no significant difference between sham-operated female birds and uropygial glandectomized female birds. In Experiment 2 the relationship between male olfaction and the females uropygial gland was investigated using olfactory bulbectomized male birds. The number of mounts and copulations of sham-operated male birds with sham-operated female bird was significantly higher than with uropygial glandectomized female birds. In contrast olfactory bulbectomized male birds showed no significant differences in the number of mounts and copulations between sham-operated female birds and uropygial glandectomized female birds. These results indicate that intact and sham-operated male birds prefer to mate with female birds with the uropygial gland. The number of courtship waltzing of sham-operated male birds showed no significant difference. However olfactory bulbectomized male birds significantly courted to uropygial glandectomized female birds. Summarizing our results show that while anosmic males did not have any preference, both intact and sham-operated male birds chose to mate with female birds having an intact uropygial gland, suggesting that mate preference involves in male olfaction and that the females uropygial gland acts as a source of social odor cues in domestic chickens.

Laminar origin of the tecto-thalamic projections in the albino rat.

Cells of origin of the tecto-LP (lateroposterior nucleus of the thalamus) projection and the tecto-LGNd (dorsal nucleus of the lateral geniculate body) projection were studied in the albino rat by means of retrograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). Tecto-LGNd neurons with small spindle form were located in the stratum griseum superficiale of the superior colliculus (SC), whereas tecto-LP neurons with polygonal shape were found in the stratum opticum of the SC.

Quantitative analysis of the lateral geniculate nucleus in the mutant microphthalmic rat

A quantitative analysis of the lateral geniculate nucleus was carried out in the mutant microphthalmic rat. In the dorsal lateral geniculate nucleus (LGNd) of the microphthalmic rat we found the total volume and neuronal population were reduced by 45 and 68% of normal values, respectively. The size of normal LGNd neurons was 8 to 20 microns and that of mutant LGNd cells from 6 to 16 microns. Neurons of the normal LGNd were medium-size and round or oval, and their cell bodies were filled with Nissl substance. Microphthalmic LGNd neurons, on the other hand, had narrow cytoplasmic spaces with few Nissl granules, and pale cell nuclei. In the microphthalmic rat, the lateral part of the ventral lateral geniculate nucleus (LGNvl) also showed a marked reduction in the total volume and neuronal population which were 42 and 76% of normal values, respectively. The size of normal LGNvl neurons was 8 to 20 microns and that of the microphthalmic neurons from 6 to 16 microns. These findings suggested that a marked reduction in the size of the LGNd and LGNvl in the mutant can be attributed to a decrease in neuronal population to a diminution of cell size.

The role of olfaction in oil preference in the chicken

The role of olfaction on the preference of diets containing 20% medium-chain (MCT) or long-chain triacylglycerol (LCT) was investigated in the chicken. Olfactory bulbectomized, sham-operated (Sham) or intact (Intact) birds were offered a choice between LCT or MCT diet and food intake was measured over a short time period. Intact and Sham groups showed a significant preference for LCT over MCT diet, but olfactory-bulbectomized chickens lost the preference for LCT over MCT. The bilateral cutting of the olfactory nerves confirmed the results taken in olfactory bulbectomy. It is concluded that olfaction plays a major role in the preference of diets containing MCT or LCT in chickens.

Pathways and terminations of axons arising in the fastigial oculomotor region of macaque monkeys

The majority of axons from the fastigial oculomotor region (FOR) decussated in the cerebellum at all rostrocaudal levels of the fastigial nucleus (FN) and entered the brainstem via the contralateral uncinate fasciculus (UF). Some decussated axons separated from the UF and ran medial to the contralateral superior cerebellar peduncle and ascended to the midbrain. Uncrossed FOR axons advanced rostrolaterally in the ipsilateral FN and entered the brainstem via the juxtarestiform body. The decussated fibers terminated in the brainstem nuclei that are implicated in the control of saccadic eye movements. In the midbrain, labeled terminals were found in the rostral interstitial nucleus of the medial longitudinal fasciculus, a medial part of Forels H-field, the periaqueductal gray, the posterior commissure nucleus, and the superior colliculus of the contralateral side. In the pons and medulla, FOR fibers terminated in a caudal part of the pontine raphe, the paramedian pontine reticular formation, the nucleus reticularis tegmenti pontis, the dorsomedial pontine nucleus of the contralateral side, and the dorsomedial medullary reticular formation of both sides. In contrast, FOR projections to the vestibular complex were bilateral and were mainly to the ventral portions of the lateral and inferior vestibular nuclei. No labeled terminals were found in the following brainstem nuclei which are considered to be involved in oculomotor function: oculomotor and trochlear nuclei, interstitial nucleus of Cajal, medial and superior vestibular nuclei, periphypoglossal nuclei, and dorsolateral pontine nucleus. Labeling appeared in the red nucleus only when HRP encroached upon the posterior interposed nucleus.

Brainstem mossy fiber projections to lobules VIa, Vib,c, VII and VIII of the cerebellar vermis in the rat

The brainstem mossy-fiber projections to lobules VIa, VIb,c, VII and VIII of the cerebellar vermis were studied by retrograde transport of horseradish peroxidase in the rat. The distribution of labeled cells indicated that these lobules received major projections from topographically different locations of the basilar pontine nuclei and the nucleus reticularis tegmenti pontis. Lobules VIa and VIII received an additional strong projection from the lateral reticular nucleus. Moderate projections were found to reach lobule VIa from the raphe pontis and external cuneate nucleus; lobules VIb,c from the raphe pontis, lateral reticular nucleus, and a group of cells in the lateral tegmentum; lobule VII from the spinal vestibular nucleus and a lateral tegmental cell group; and lobule VIII from the medial and spinal vestibular nuclei, nucleus intercalatus and Roller of the perihypoglossal nuclei, and the main cuneate nucleus. The quantitative and topographical differences in the origin of mossy fibers suggest that these lobules may subserve slightly different functions.

Spontaneous discrimination of food quantities in the jungle crow, Corvus macrorhynchos

Despite considerable research on numeric judgements in animals, uncertainty remains about both the underlying mechanisms and the role of training. To address these issues, we study quantity discrimination in jungle crows that have previously been shown to select the larger of two quantities following training. In the current study, we examined whether jungle crows are able to discriminate between different quantities of food items without prior training. Using a simultaneous two-alternative test, we studied whether their performance reveals the underlying mechanism being used for discrimination of small and large quantities in other animals. First, jungle crows were tested with a choice between two discrete homogeneous quantities; one smaller and one larger, with ratios of 0.5 (1 versus 2, 2 versus 4 and 4 versus 8), 0.67 (2 versus 3, 4 versus 6 and 8 versus 12) and 0.75 (3 versus 4, 6 versus 8 and 12 versus 16). Then, we conducted a test using a non-numerical cue where the volume of comparison stimuli was equalized. Jungle crows selected the larger of the two quantities in all comparisons, except those when both quantities were large (6 versus 8, 8 versus 12 and 12 versus 16). Furthermore, accuracy of selection of the larger quantity declined with increasing numerical magnitude. These results suggest that in a spontaneous discrimination task, jungle crows use an object-file mechanism to compare quantities, even when the number of items in one of the arrays exceeds four. The crows showed no preference for the smaller or the larger quantity when the volume cue was removed. This lack of bias may suggest an ecological role of selection for a patch with higher amounts of food and not necessarily the exact number of food items for optimal foraging in jungle crows.

Cerebellar corticonuclear and nucleocortical projections in the vermis of posterior lobe of the rat as studied with anterograde and retrograde transport of WGA-HRP

Corticonuclear (CN) and nucleocortical (NC) projections of the cerebellum were studied in rats by using antero- and retrograde transport of wheatgerm agglutinin-conjugated horseradish peroxidase (WGA-HRP). Following minute injections of WGA-HRP in different folia for vermal lobules VI-VIII, a rostrocaudal topography was observed in the CN projection; lobules VIa and VIb, c projected to distinctly separate areas in the ipsilateral fastigial nucleus (FN): VIa projected to the ventral part of the medial subdivision of the FN (FNm), whereas VIb, c projected to the dorsocaudal part of the caudomedial subdivision of the FN (FNcm) and to the caudal FNm. The terminals from lobules VIb, c and VII occupied partially overlapping areas in the caudal part of the ipsilateral FNcm and FNm. A few terminal fibers were also seen in the dorsolateral protuberance of the FN (dlp). The fibers from vermal lobule VIII terminated in the ipsilateral rostral FNcm and in the FNm. The latter terminal area was divided into two parts: a smaller dorsal and a larger ventral part that in turn overlapped almost completely with the terminal area of fibers from lobule VIa. Retrogradely labeled fastigial neurons were found in the areas of the FN where Purkinje-cell (P-cell) axons from the respective injection sites terminated. In addition, retrogradely labeled fastigial neurons were scattered in areas outside the P-cell terminal fields on the injection side and in the contralateral FN.

Topographical organization of the olivocerebellar projection upon the posterior vermis in the rat

Projections from the medial accessory olive (MAO) to lobules VI, VII and VIII of the cerebellar vermis were investigated in the rat using the retrograde transport of wheatgerm agglutinin-conjugated horseradish peroxidase (WGA/HRP). When WGA/HRP was injected into the anterior half of lobule VI (VIa), retrogradely labeled neurons were found in a relatively narrow zone which traversed approximately the middle of the MAO and a portion of the nucleus beta. In contrast, injection into the posterior half of lobule VI (VIb, c) resulted in labeling of neurons in the medial and lateral portions of the MAO and in the nucleus beta. When HRP was confined to lobule VII, labeled neurons were found in the medial portion of the caudal MAO. No labeled neurons were found in the nucleus beta. When the injection was restricted to lobule VIII, labeled neurons appeared along the caudal end of the MAO. There were many labeled neurons in the nucleus beta. The central portion of the caudal MAO was free of labeled neurons unless the enzyme encroached upon a part of the anterior lobe. Thus, the projection areas to lobules VI-VIII formed a circle surrounding the free area and each of the lobules received fibers from a well-circumscribed portion: lobules VI-VIII received projections from the rostral, medial and caudal portion of the imaginary circle, respectively. The lateral portion was shared by the areas projecting to lobules VI and VIII. In addition, these lobules received projections also from an overlapping area in the nucleus beta.