Gerald E. Schneider

Olfactory Bulb Removal Eliminates Mating Behavior in the Male Golden Hamster

Mating behavior in sexually naive and sexually experienced male golden hamsters was totally eliminated by removing their olfactory bulbs. In contrast, the mating behavior in blinded, unilaterally bulbectomized, and sham-operated controls was essentially normal. Testosterone injections restored normal sexual behavior in castrated controls but had no effect on the bilaterally bulbectomized animals.

Contrasting visuomotor functions of tectum and cortex in the golden hamster

ZusammenfassungVisuell gesteuerte Orientierung (räumliche Lokalisation) und visuelles Unterscheidungsvermögen beim Goldhamster werden durch Hirnläsionen funktionell getrennt. Nach Entfernung der Sehrinde können die Tiere keine visuellen Musterunterscheidungen, wohl aber noch in fast normaler Weise visuelle Objektlokalisationen vornehmen. Entfernung des Colliculus superior führt zu entgegengesetzten Effekten: die Tiere können sich nicht mehr nach der Position eines visuellen Reizes orientieren, zeigen aber trotzdem ausgezeichnete Musterunterscheidung.SummaryVisually-guided orientation (spatial localization) and visual discrimination were dissociated by means of brain lesions in the golden hamster. After ablation of visual cortex, hamsters failed to discriminate visual patterns, but showed nearly normal ability to localize an object in space by means of vision. Ablation of the superior colliculus produced opposite effects: these animals were completely unable to orient to the position of a visual stimulus, but nevertheless showed excellent pattern discrimination.

Mechanisms of functional recovery following lesions of visual cortex or superior colliculus in neonate and adult hamsters.

Brain damage inflicted early in life can have both behavioral and neuroanatomical consequences which differ from the effects of lesions in the adult. The experimental results reported here clarify some of these differences, and narrow the range of tenable hypotheses concerning the roles of subcortical visual pathways in functional recovery from cortical and midbrain tectal lesions. Lesions of superior colliculus or visual cortex in the adult Syrian golden hamster (Mesocricetus auratus) have clearly distinguishable consequences in visually guided behavior [SCHNEIDER, 1966, 1967, 1969]. To human observers, who spend much of their time looking at the behavior of fellow primates, the hamster is not an ovenvhelmingly visual animal, but he is more obviously visual than the laboratory rat and has a superior colliculus more accessible to a direct surgical approach [SCHNEIDER, 1966]. Moreover, the hamsters colliculus is about as large in surface area as area 17 of the neocortex; and the superficial gray layer of the colliculus, throughout which optic tract terminals are found, has a volume more than twice as great as that of the dorsal nucleus of the lateral geniculate body (unpublished data).

Postnatal development of retinal projections in Syrian hamsters: a study using autoradiographic and anterograde degeneration techniques.

Abstract (1) In the Syrian hamster, there is a delay between the laying down of the trajectory of the optic tract (principally a prenatal event) and the formation by the optic tract of its various dense terminal projections (principally a postnatal event): At birth (Day 0), crossed retinofugal axons already cover the lateral geniculate body and extend into the superior colliculus. Although pioneering retinal efferents enter their target nuclei before Day 3, robust development of retinofugal axon telodendria is apparently delayed until that date; the onset of this arborization occurs simultaneously in the lateral geniculate body and superior colliculus, even though the axons of the optic tract pass over the lateral geniculate body before they arrive in the superior colliculus. (2) In all structures receiving binocular projections except the suprachiasmatic nucleus, the development of uncrossed optic tract axons lags behind the development of the crossed axons. (3) In regions where optic tract axons terminate in precise retinotopic order, the projections of the two eyes are segregated in adult animals, and the definitive patterns of connection develop gradually from less differentiated patterns: In the dorsal nucleus of the lateral geniculate body, crossed optic tract axons initially fill the entire nucleus, overlapping with the uncrossed axons; subsequently they withdraw from the ipsilateral projection zone, as the terminal distributions of uncrossed axons increase in density and volume. In adult hamsters, much of the uncrossed retinal input to the superior colliculus is distributed in multiple discrete clusters. Initially the clusters are not present, but develop gradually from a more diffuse pattern. (4) Since the adult distributions of crossed and uncrossed retinofugal projections are established before the time when the eyes open (Day 14), the factors which determine these distributions appear to be independent of exposure to patterned visual input. (5) In neonatal hamsters, as in adults, different populations of retinofugal axons may be distinguished by their differential rates of degeneration. (6) Some of the developmental changes in the hamsters retinal projections are similar to ontogenetic phenomena reported for other populations of central and peripheral axons.

Is it really better to have your brain lesion early? a revision of the “Kennard Principle” ☆

Abstract Redirected growth of the optic tract in hamsters with lesions of the midbrain tectum at birth results in anomalous retinal projections with correlated functional effects; these include a sparing of visually elicited turning responses which are lost after comparable lesions in adulthood. However, the animals sometimes overshoot or undershoot the target, and the responses are slow to be completed. In cases of early unilateral lesions, an optic tract projection to the wrong side of the midbrain is correlated with turning in the wrong direction in response to stimuli in specific locations. These misdirected movements can be enhanced by reward or suppressed by non-reward, or abolished by surgical section of the abnormal pathway in the mature animal. Principles derived from the experiments with animals allow us to predict that specific lesions in fetal and neonatal humans will cause particular patterns of altered growth of neuroanatomical pathways. These alterations can be expected to cause behavioral anomalies, not only in sensorimotor functions, but also in cognitive functions and in emotional responses and expression; some neuropsychological findings can be interpreted in this manner.

Topography of visual and somatosensory projections to the superior colliculus of the golden hamster

The topography of visual and somatosensory projections to the superior colliculus in the Syrian hamster was studied using electrophysiological techniques. The visual projection to the superficial layers of the colliculus is similar in general topography to that described for other rodents. The magnification of the visual field on the colliculus surface was greatest for nasal visual field. The magnification factor paralleled retinal ganglion cell density for corresponding visual field sectors. In the deep layers of the colliculus, a somatosensory projection is found in register with the visual projection such that the anterior somatosensory field and nasalmost visual field are both represented in rostral colliculus; posterior somatosensory fields and temporal visual fields are found in caudal colliculus. Likewise, upper visual and somatosensory fields are found in medial colliculus, and lower visual and somatosensory fields are found in lateral colliculus. Large receptive fields make the somatosensory topography less precise than the visual topography, but this lack of precision could serve to keep the two maps generally in register during eye and body movements.

Retrograde cortical and axonal changes following lesions of the pyramidal tract

Following lesions of the pyramidal tract in hamsters, retrograde changes were studied in the sensorimotor cortex and in the pyramidal tract axons proximal to the lesion, at survival times ranging from 2 weeks to 14 months. Severe cell shrinkage occurred in layer 5 pyramidal neurons as early as 2 weeks, but there was no cell loss among these neurons even with long survival times. Use of the Fink-Heimer method for degenerating axons revealed that the pyramidal tract proximal to the lesion had undergone a retrograde axon degeneration which, in some respects, resembled anterograde degeneration. The retrograde axon degeneration began at the lesion site and advanced slowly rostralwards with time involving increasingly greater numbers of fibers. However, even at the longest survival times the degeneration fell off markedly at pontine levels. The results indicate that this process represents a true retrograde fiber degeneration (as opposed to an indirect Wallerian degeneration) which appears to reach a point of equilibrium such that a partially shrunken pyramidal cell is maintaining a partially degenerated axon.

Motivation driven learning for interactive synthetic characters

Adaptation capability and a transparent motivation system greatly aid real time interactions between humans and synthetic characters. These components enhance the life-like impression that the characters make, and enable comfortable communication between the characters and human participants. We extended the behavioral action selection system of Blumberg[2] and Kline[14] with these needs in mind, and developed a creature kernel that enables the designing of a character with communicative motivational and emotional states, and learning abilities based on feedback from the motivation system. In this paper, we introduce this new approach to character design, and how various learning algorithms have been incorporated within this framework. The main characters for an interactive installation, (void*): A cast of characters, have been created using this developed creature kernel. We describe results with examples of alteration of attitudes, learning of concepts, and formation of emotional reactions to locations based on experience.

Initial stages of retinofugal axon development in the hamster: evidence for two distinct modes of growth

SummaryIn order to characterize differences in growth patterns of axons as they elongate toward their targets and during the initial stages of terminal arbor formation within the targets, we examined the primary visual system of fetal and newborn hamsters using three morphological methods: the Cajal-deCastro reduced silver method, the rapid Golgi technique, and anterograde transport of HRP. Axons emerge from the retina between the 10th and 11th embryonic days (E10–E11). The front of retinal axons crosses the chiasm, extends over the primitive dorsal nucleus of the lateral geniculate body (LGBd) by E13, and advances to the back of the superior colliculus (SC) by E13.5–E14. The rate of axon growth during this advance is nearly 2 mm/day. Collateral sprouts appear on axons around E15.5. In the LGBd and SC, these sprouts arise from multiple sites along the parent axons. Only one or a few of the sprouts continue to grow and branch, while others are eliminated. The net rate of axon collateral advance in this second phase is an order of magnitude slower than during the stage of axon elongation. Thus, formation of CNS projections may involve two qualitatively distinct modes of axon growth. The arborization mode contrasts with the elongation mode by the presence of branching, a lack of fasciculation and a slower average rate of extension. The Stereotypic direct advance of axons during elongation also differs from the remodelling which occurs during arborization. The delay between axon arrival at targets and onset of arborization could be a reflection of axons “waiting” for a maturational change to occur in the retina or in targets. Arborization in the LGBd and SC is initiated around the same time, implicating the former possibility. However, a slower differentiation of retinal arbors in the SC, in addition to morphological differences of arbors in the two structures, suggests that alterations in substrate factors also play a critical role in triggering the early stages of arbor formation.

Abnormal recrossing retinotectal projections after early lesions in Syrian hamsters: age-related effects.

If the superficial layers of the right superior colliculus (SC) of a newborn hamster are removed, fibers from the left eye not only terminate in the surviving deeper layers of the right SC, but also cross the tectal midline and terminate in the medial third of the left SC. If the right eye is also removed at birth, the abnormally recrossing fibers from the left eye will spread over the entire surface of the left SC31. In this series of experiments, we ablated the right SC of hamsters at birth, but enucleated the right eye on different days postnatally in order to examine the spreading of the axon terminal pattern as a function of age. When the animals were young adults, the pattern of retinofugal projection of the left eye was traced using the Fink-Heimer technique or with autoradiography. It was found that the projections from the left eye continue to spread over the entire left SC when the right eye was removed up until day 10, though their distribution was more sparse when the eye was removed on days 7-10 than when it was removed on days 0-6. When the removal of the right eye was delayed until day 12, the lateral spreading of recrossing axons was markedly reduced. When the right eye was removed on day 14, the distribution of the projections from the left eye was restricted to the medial third of the left SC, just as if no early eye removal had been performed. It appears that after a critical age is reached, even when terminal space is available the axons and axon terminals will not move, at least not over any appreciable distance.