摘要:

In adult hedgehogs with large unilateral cortical deposits of fluorescent somatopetal tracers, labelled perikarya were found not only in the ipsilateral but also contralateral thalamus. An exceptionally large number of contralaterally labelled neurons was seen in the ventrolateral nucleus, also at a considerable distance from the midline. Deposits of one of two different tracers in the frontoparietal cortex of each hemisphere appear to label different perikarya in each ventrolateral nucleus. This projection to the contralateral cortex in hedgehogs does not resemble thalamo-cortical connections in either adult or developing brains of other mammalian species. Among amniotes, only in pigeons have contralateral projections from the thalamus to the telencephalon been described. The somatosensorimotor system of hedgehogs may be the only known mammalian remnant of primitive vertebrate thalamocortical organization. Whether primitive or derived, the bilateral thalamocortical projection in hedgehogs shows that hedgehog brains cannot be uncritically taken to represent brains of primate ancestors.

ISSN:0006-8977    

DOI:10.1159/000114123

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

Play is a distinctive behavior of young mammals, especially mammals with a well-developed forebrain. For this reason it is thought that there may be a relation between forebrain evolution and highly elaborated play behavior. This study investigated the contribution of the cortex to play behavior by comparing play in control and neonatally decorticated rats (Rattus norvegicus). Play fighting in rats involves the combination of attack by one rat and defense by the recipient, with pinning arising when specific patterns of defense are used. Whether paired with another decorticate or with an intact pairmate, decorticates attacked pairmates as frequently as did intacts, and they were just as likely to defend against playful attacks as were intacts. Where decorticates differed from intacts was on a measure of pinning, in which one rat stands over a supine partner, decorticate rats displayed a reduction of 50% relative to control rats during the juvenile stage in which play is most pronounced (days 25 to 40). Juvenile decorticate rats adopted types of defensive responses which were less likely to result in the pinning configuration. Thus, a reduced pinning frequency reflects an altered pattern of defense, not a reduced level of play fighting. Rather, the decorticate patterns of defense were typical of those defensive responses displayed by adult rats. That is, decorticate juveniles exhibit a precociously mature pattern of playful defense. As intact controls mature, they come to resemble the decorticates in their defensive responses, and hence the difference in pinning frequency between decorticate and intact pairs diminishes. This suggests that the cortex may inhibit the escalation of defense in juveniles and thus promote prolonged ventral-ventral contact during play fighting. The results further suggest that the cortex is involved in the development of adult behavioral skills by facilitating juvenile play.

ISSN:0006-8977    

DOI:10.1159/000114124

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

Adult, female praying mantids, Sphodromantis lineola l[2]) for which l(2) = 1.5–6 mm. ''Anti-worm'' lures (l[1]

ISSN:0006-8977    

DOI:10.1159/000114125

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

Horizontal eye movements in response to vestibular and optokinetic stimulation were investigated in 20 species of marine and fresh water teleosts. Most species performed spontaneous saccadic eye movements in light and in darkness. Successive saccades occurred either at irregular intervals and in different directions (few species), or in bursts of smaller saccades in one direction followed by saccades in the opposite direction (majority of species). Thus, in the latter group the lines of sight shifted cyclically from one side to the other about every 10–15 s. Eye movement responses in goldfish and toadfish were prototypical for two major functional groups. Optokinetic and vestibular nystagmus in the goldfish were much more regular and attained significantly higher gains than in the oyster toadfish. Optokinetic afternystagmus (OKAN) and perVpostrotatory nystagmus lasted about 10–12 s in the goldfish, but only 2–3 s in the oyster toadfish. Bilateral labyrinthectomy in goldfish resulted in optokinetic gains and OKAN durations that were very close to those of intact toadfish. These results indicate the presence (in goldfish) and the absence (in toadfish) of a functioning velocity storage network, respectively. Other non-ostariophysan teleosts failed to show a ''goldfish-like'' response pattern as well. Ostariophysan species differed in their reflex performance as well. A ''gold-fish-like'' response pattern was observed in five of the seven cypriniform species and in two of the four characiform species but not in the four siluriform species. Positively correlated, combined response properties suggest that some species are better equipped for gaze stabilization at higher velocities than other species. These behavioral differences may parallel different specializations in locomotor pattern and mode of life. Absence of a functioning velocity storage network in bottom-dwelling teleosts (as in Amphibia) may be related to the sporadic, slow locomotion of these species and the resulting small requirements for continuous gaze stabilization during self-motion at higher veloc

ISSN:0006-8977    

DOI:10.1159/000114126

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

In order to test the usefulness of the in vitro HRP-labeling technique in the brains of small lizards, the fasciculus retroflexus was labeled in isolated brains of young specimens of the lizard Gallotia galloti by means of HRP applied with the tip of a micropipette located approximately midway along the descending course of the tract. Cells in the medial and lateral habenular nuclei were labeled retrogradely. Anterograde transport showed the course of the fasciculus retroflexus, first dorsoventrally into the paramedian prerubral tegmentum and then longitudinally into the isthmic nucleus interpeduncularis. Some fibers spread dorsally into the mesencephalic and isthmic tegmental fields. A substantial bundle continues caudally into nucleus raphe parvocellularis. Other fibers diverge rostral-wards from the point of inflexion of the fasciculus, coursing longitudinally in the medial forebrain bundle into the basal telencephalon. Some fibers course rostrally from the nucleus habenularis lateralis in the stria medullaris and could be followed to the dorsal septum.

ISSN:0006-8977    

DOI:10.1159/000114127

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

Afferents to the habenular complex were studied by means of in vitro horseradish peroxidase retrograde labeling and anterograde control experiments in the lizard Gallotia galloti. The medial habenular nucleus was found to receive abundant afferent fibers from the nucleus of the posterior pallial commissure and the nucleus septalis impar. More restricted input comes from the nucleus eminentiae thalami and the nucleus of the stria medullaris. The lateral habenular nucleus is innervated by various fiber groups originating from the bed nucleus of the anterior commissure, the diagonal band nucleus, the lateral preoptic area, the anterior entopeduncular nucleus, the lateral hypothalamic and mammillary areas, the nucleus of the stria medullaris, the area tegmentalis ventralis and a scattered neuronal subpopulation in the large-celled dorsolateral nucleus of the dorsal thalamus. Habenulopetal fibers generally follow the stria medullaris, but hypothalamic, entopeduncular and dorsal thalamic afferents course through the dorsal peduncle of the lateral forebrain bundle in a transthalamic route. Mesencephalic ventral tegmental afferents ascend through the tractus retroflexus.

ISSN:0006-8977    

DOI:10.1159/000114128

出版商:S. Karger AG    

年代:1992

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000114129

出版商:S. Karger AG    

年代:1992

数据来源: Karger