bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interhemispheric neocortical connections of the corpus callosum in the normal mouse: A study based on anterograde and retrograde methods
Authors: Yorke C. H. , Caviness V. S. 
Published: May 2005

AbstractInterhemispheric neocortical connections are widely distributed through the corpus callosum in the mouse. Callosal connections are present in all cytoarchitectonic fields except field 25. The distal extremity representations of SmI, and MsI the representation of the mystacial vibrissae in SmI, and the more peripheral field representation of VI are relatively acallosal. Dense projections lie in the midline or truncal representations of SmI, MsI, SmII, at the vertical meridian representations bordering field 17, and medial to the AI representation. The radial distribution of terminals is bimodal in most cytoarchitectonic fields. It is unimodal in the supracallosal segment of field 29b and fields 49 and 27, trimodal in fields 13 and 35.The cells of origin of callosal fibers appear to have the same topographic pattern of distribution as the callosal terminals, observing the same steep and gradual density gradients. No cells giving rise to callosal axons are identified in the acallosal regions of fields 2 and 17. Further, superficial focal lesions in cortical areas which receive callosal connections give rise only to homotopic contralateral degeneration. Acallosal areas of 17 and 2 give rise to no callosal connections. The cells of origin of callosal connections are located at all laminar levels of the cortex and include pyramidal and polymorphic cells but not the granule cells of layer IV.
Anatomical identification of a telencephalic visual area in crocodiles: Ascending connections of nucleus rotundus in Caiman crocodilus
Authors: Pritz Michael B. 
Published: May 2005

AbstractNucleus rotundus receives a major input from the optic tectum in crocodiles, Caiman crocodilus. Telencephalic projections of nucleus rotundu were studied in Caiman by means of the Fink‐Heimer procedure after anodal, stereotaxic lesions. Efferent axons of nucleus rotundus assemble on the ventrmedial aspect of this nucleus and swing ventrolaterally to enter the dorsal peduncle of the lateral forebrain bundle. These ascending fibers continue rostrally in the dorsal peduncle of the lateral forebrain bundle to enter the telencephalon where they remain restricted to a lateral portion of the lateral forebrain bundle. At more anterior levels, these fascicles turn dorsally, pass through the ventrolateral area, and terminate massively in a lateral part of the rostral dorsolateral area.The results of this experiment are compared with similar studies on thalamotelencephalic connections of diencephalic visual areas in other amniotes. Parallels in fiber connections of thalamic auditory and visual areas and the segregation these modalities in the telencephalon of Caiman are discussed. These similarities in neural circuitry and synaptic elements of auditory and visual systems that synapse in the midbrain of Caiman form the basis for a different interpretation of sensory system organization in amniotes.
Organization and development of brain stem auditory nuclei of the chicken: Organization of projections from N. magnocellularis to N. laminaris
Authors: Parks Thomas N. , Rubel Edwin W. 
Published: May 2005

AbstractThe tonotopic and topographic organization of the bilateral projection from second‐order auditory neurons of nucleus magnocellularis (NM) to nucleus laminaris (NL) was examined in young chickens. In one group of birds, the NM axons which innervate the contralateral NL were severed by cutting the crossed dorsal cochlear tract at the midline. Heavy terminal degeineration in NL was confined to the neuropil area immediately ventral to the perikaryl lamina. Very little degeneration was seen in the dorsal neuropil region. In a second series of animals, the characteristic frequency (CF) of cells in an area of NM was first determined by microelectrode recording techniques and then a small electrolytic lesion was made through the recording electrode. Following survival periods of 24–48 hours, the distribution of projections from the lesioned area to the ipsilateral and contralateral NL was examined usinig the Fink‐Heimer method.As previously described in the pigeon, projections from NM terminate densely in the neuropil region immediately dorsal to the ipsilateral NL cell bodies and ventral to the perikaryl layer on the contralateral side, providing each NL neuron with segregated binaural innervation. Lesions in any area of NM produced degeneration confined to a limited caudo‐rostral and medio‐lateral portion of both laminar nuclei. To investigate this topographic relationship, the caudorostral extents of the lesion in NM and of the resulting degeneration in both NL were determined. Linear regression and correlation analyses then related these positional values to each other and to the CF found at the center of each lesion. All correlations were highly significant and ranged from 0.78 between the position of the lesion in NM and CF to 0.91 between the caudo‐rostral position of degeneration in the NL ipsilateral and contralateral to the lesion.It is concluded that neurons in NM project in a very discrete topographic, tonotopic and symmetrical fashion to NL on both sides of the brain, contributing to the binaural response properties and tonotopic organization of neurons in NL. The results also suggest that the organization of projections from NM to NL could provide a mechanism for the differential transmission delay required by a “place” model of low‐frequency sound localization.
Autoradiographic studies of cerebellar histogenesis in the bullfrog tadpole during metamorphosis: The external granular layer
Authors: Gona Amos G. 
Published: May 2005

AbstractSpontaneously metamorphosing bullfrog tadpoles and those induced to metamorphose by injections of thyroid stimulating hormone (TSH) were given a single intraperitoneal injection of thymidine‐3H (10 μCi/g body weight). The brains were dissected out at various periods 3 hours to 14 days later, and processed for autoradiography. At the 3‐hour interval after thymidine‐3H injection, ependymal cells were labelled, but not the external granular layer (EGL) cells. Furthermore, in all the metamorphosing tadpoles intense labelling was restricted to the ependyma of the marginal region of the cerebellar plate. At 48 hours, labelled cells were seen in the EGL of the marginal region. At the 4‐day interval, most of the EGL was labelled, and labelled cells were also seen migrating from the EGL into the internal granular layer (IGL). By 14 days, several labelled cells were seen in the IGL. Although the sequence of cerebellar histogenesis in the frog is similar to the general pattern described in other vertebrate groups, the results indicate that the EGL of the frog cerebellum does not serve the function of a secondary proliferating zone.
Projections of the optic tectum in two teleost species
Authors: Ebbesson Sven O. E. , Vanegas Horacio 
Published: May 2005

AbstractThe efferent pathways of the optic tectum have been investigated in the percomorph Eugerres and the berycomorph Holocentrus. A portion of the dorsal‐dorsolateral region of the optic tectum was unilaterally resected by suction. The animals were perfused 6–30 days thereafter, and the brains were processed according to a modification (Method 7 in Ebbesson, '70) of the Fink‐Heimer ('67) technique for the selective silver impregnation of degenerating axons and terminals.Three groups of fibers emerge from the lesioned region: (a) a medial group, which runs towards the midline and terminates in the ipsilateral torus longitudinalis and the contralateral tectum; (b) an ascending group, which enters the dorsocaudal region of the diencephalon and terminates in pretectal cell groups, in the dorsomedial optic thalamic nucleus, and in the nucleus rotundus or prethalamicus; and (c) a descending group, which funnels down into the midbrain tegmentum. Here abundant terminals are given to dorsolateral cell groups and to the nucleus isthmi. A recurrent fascicle leaves the mainstream and ascends to terminate in scattered diencephalic cell groups, in the nucleus geniculatus posterior pars ventralis, and in the nucleus rotundus or prethalamicus. The bulk of descending fibers then forms an ipsilateral bundle, which gives terminals to the lateral reticular formation of mesencephalon and rhombencephalon, and a contralateral (i.e., the predorsal) bundle, which terminates in the medial reticular formation of mesencephalon and rhombencephalon.
Scotopic and photopic vision in the california ground squirrel: Physiological and anatomical evidence
Authors: Jacobs Gerald H. , Fisher Steven K. , Anderson Don H. , Silverman Martin S. 
Published: May 2005

AbstractThe California ground squirrel is a highly diurnal species previously thought to have an all‐cone retina. This issue was re‐examined in physiological and anatomical experiments. The electroretinogram (ERG) was used to measure the spectral sensitivity of the eye under different conditions of adaptation. The occurrence of a Purkinje shift could be demonstrated, although there was some indication that not all members of this species show such a shift. Spectral sensitivity of the dark‐adapted eye of this squirrel is close to that predicted by a typical mammalian rhodopsin. Light adaptation produces a shift in spectral sensitivity to a peak location of about 525 nm. It was shown that two mechanisms having different spectral sensitivities contribute to the photopically recorded ERG. The degree to which these two mechanisms contribute to the ERG was found to be strikingly different from the degree to which the two contribute to visual behavior.Our anatomical results indicate that the retina of the California ground squirrel has two structurally distinct photoreceptors which, on the basis of various criteria, can be classified as cone and rod‐like. The rod‐like receptors comprise about 6–7% of the total. The two photoreceptor types differ in placement of their inner segments, size of their outer segments, outer segment ultrastructure, and terminal structure and organization.
Nigrothalamic projections in the monkey demonstrated by autoradiographic technics
Authors: Carpenter Malcolm B. , Nakano Katsuma , Kim Ronald 
Published: May 2005

AbstractIn spite of repeated demonstrations by degeneration technics, nigrothalamic fibers have been regarded with some skepticism. Attempts were made to trace‐ nigral efferent projections in the monkey by autoradiographic technics. Tritiated amino acids (L‐leucine, L‐lysine and L‐proline), injected into portions of the substantia nigra (SN), labeled cells in four regions, designated as, (1) rostrolateral, (2) caudolateral, (3) rostromedial and (4) central.Rostrolateral nigral neurons transported radioactive label preferentially and abundantly to thalamic nuclei; localized isotope was found in parts of three thalamic nuclei, the medial part of the ventral lateral nucleus (VLm), the magnocellular part of the ventral anterior nucleus (VAmc), and the paralaminar part of the dorsomedial nucleus (DMpl).Lateral neurons in the caudal half of the SN transmitted radioactive label to the same thalamic nuclei as rostrolateral nigral neurons. Isotope transported to portions of the striatum was modest and localized. Radioactive label taken up by large cells in the caudal third of the SN was transported to portions of the striatum, but not to thalamic nuclei.Labeled nigral neurons in the medial two‐thirds of the rostral half of the SN, and in the middle third of the central part of the SN, transported the label mainly to parts of the caudate nucleus and putamen. In these animals modest radioactive label was seen in VLm and VAmc, but not in other thalamic nucleus.There was no evidence that nigral neurons project to the subthalamic nucleus. No radioactive transport from nigral neurons was detected in the superior colliculus, the midbrain tegmentum, or the red nucleus, and none was transported to more caudal brain stem nuclei.Nigrothalamic fibers arise particularly from cells in rostral and lateral parts of the substantia nigra. While some cells in other parts of the nigra project to thalamic nuclei, these appear scattered and less numerous. Large cells in caudal parts of the SN do not project to thalamic nuclei. These observations confirm nigrothalamic projections to VLm and VAmc, and identify a new nigral projection to part of the dorsomedial nucleus of the thalamus (DMp1). No nigral efferent fibers project to any of the intralaminar thalamic nuclei.
Central control of song in the canary, Serinus canarius
Authors: Nottebohm Fernando , Stokes Tegner M. , Leonard Christiana M. 
Published: May 2005

AbstractWe have traced central nervous pathways controlling bird son in the canary using a combination of behavioral and anatomical techniques. Unilateral electrolytic brain lesions were made in adult male canaries whose son had been previously recorded and analysed on a sound spectrograph. After severral days of postoperative recording, the birds were sacrificed and their brains processed histologically for degeneration staining with the Fink‐Heimer technique. Although large lesions in the neostriatum and rostral hyperstriatum had no effect on song, severe song deficits followed damage to a discrete large‐celled area in the caudal hyperstriatum ventrale (HVc). Degenerating fibers were traced from this region to two other discrete nuclei in the forebrain: one in the parolfactory lobe (area X, a teardrop‐shaped small‐celled nucleus) and a round large‐celled nucleus in the archistriatum (RA). Unilateral lesions of X had no effect on song; lesions of RA, however, caused severe song deficits. Degenerating fibers from RA joined the occipitomesencephalic tract and had widespread ipsilateral projections to the thalamus, nucleus intercollicularis of the midbrain, reticular formation, and medulla. It is of particular interest that direct connections were found onto the cells of the motor nucleus innervating the syrinx, the organ of song production. Unilateral lesions of n. intercollicularis (previously implicated in the control of vocal behavior) had little effect on song.One bilateral lesion of HVc resulted in permanent (9 months) and complete elimination of the audible components of song, although the bird assumed the posture and movements typical of song. Preliminary data suggest that lesions of the left hemisphere result in greater deficits than lesions of the right one. This finding is consistent with earlier reports that the left syrinx controls the majority of song components. Results reported here suggest a localization of vocal control in the canary brain with an overlying left hemispheric dominance.
Amygdaloid projections to subcortical structures within the basal forebrain and brainstem in the rat and cat
Authors: Krettek J. E. , Price J. L. 
Published: May 2005

AbstractThe efferent fiber connections of the nuclei of the amygdaloid complex with subcortical structures in the basal telencephalon, hypothalamus, midbrain, and pons have been studied in the rat and cat, using the autoradiographic method for tracing axonal connections. The cortical and thalamic projections of these nuclei have been described in previous papers (Krettek and Price, ′77b,c). Although the subcortical connections of the amygdaloid nuclei are widespread within the basal forebrain and brain stem, the projections of each nucleus have been found to be well defined, and distinct from those of the other amygdaloid nuclei.The basolateral amygdaloid nucleus projects heavily to the lateral division of the bed nucleus of the stria terminalis (BNST), to the caudal part of the substantia innominata, and to the ventral part of the corpus striatum (nucleus accumbens and ventral putamen) and the olfactory tubercle; it projects more lightly to the lateral hypothalamus. The central nucleus also projects to the lateral division of the BNST and the lateral hypothalamus, but in addition it sends fibers to the lateral part of the substantia nigra and the marginal nucleus of the brachium conjunctivum. The basomedial nucleus has projections to the ventral striatum and olfactory tubercle which are similar to those of the basolateral nucleus, but it also projects to the core of the ventromedial hypothalamic nucleus and the premammillary nucleus, and to a central zone of the BNST which overlaps the medial and lateral divisions. The medial nucleus also projects to the core of the ventromedial nucleus and the premammillary nucleus, but sends fibers to the medial division of the BNST and does not project to the ventral striatum. The posterior cortical nucleus projects to the premammillary nucleus and to the medial division of the BNST, but a projection from this nucleus to the ventromedial nucleus has not been demonstrated. Projections to the “shell” of the ventromedial nucleus have been found only from the ventral part of the subiculum and from a structure at the junction of the amygdala and the hippocampal formation, which has been termed the amygdalo‐hippocampal area (AHA). The AHA also sends fibers to the medial part of the BNST and the premammillary nucleus.Virtually no subcortical projections outside the amygdala itself have been demonstrated from the lateral nucleus, or from the olfactory cortical areas around the amygdala (the anterior cortical nucleus, the periamygdaloid cortex, and the posterior prepiriform cortex). However, portions of the endopiriform nucleus deep to the prepiriform cortex project to the ventral putamen, and to the lateral hypothalamus.
Intratrigeminal and thalamic projections of nucleus caudalis in the squirrel monkey (Saimiri sciureus): A degeneration and autoradiographic study,
Authors: Ganchrow Donald 
Published: May 2005

AbstractIn order to test the hypothesis that thalamic efferents of trigeminal nucleus caudalis (NC) are the cranial analogue of the spinothalamic system, lesion and autoradiographic studies were carried out in the squirrel monkey, and the terminal projection fields in thalamus were noted. Results showed that NC, including lateral reticular formation (LRF), projects to contralateral VPM, the VPM‐VPL border and medial VPL, and a region dorsal to ventroposterior nucleus (VP) proper which contains cells larger than those in VPM yet which stain as darkly as VPL neurons; this latter zone of termination may be homologous with VPLo (Vim) in other species, which is that area receiving lemniscal and cerebellar afferents (Mehler, '71; Walsh and Ebner, '73; Boivie, '74). In addition, a small projection is noted in an area intercalated between dorsomedial MG, limitans nucleus and posterior VP which closely agrees with the medial division of Posterior nucleus (Po) described in rhesus and squirrel monkey (Burton and Jones, '76). No terminations were observed in the gustatory nucleus medial to VPM.Bilateral, terminal projection fields were observed in posterior mediodorsal nucleus (MD), and a paralaminar area (PL) which lies in the ventrolateral strip of MD and is particularly prominent in primates; other bilateral fields were noted in CL, particularly the more medial segment of the nucleus. A sparse projection was noted in contralateral CM. Ipsilateral, intratrigeminal connections between NC and main sensory nucleus (MSV) also were observed.We conclude that, in the squirrel monkey, NC efferents, probably including LRF, may be considered analagous to the spinothalamic system by virtue of terminations in older medial and newer ventroposterior thalamus. Terminations in posterior MD may be specific to Primates. Moreover, projections to an area just dorsal to VP proper in squirrel monkey may be included within the broader definition of a neo‐spinothalamic area as reflected in spinothalamic tract projections to the ventrolateral complex in cat (Boivie, '71b; Jones and Burton, '74). The small NC projection to a part of Po is consistent with spinothalamic terminations to a “posterior” thalamic area in other primates (Mehler, '69), and with the suggestion that medial Po transmits pain information (Burton and Jones, '76).
Role of visual experience in postcritical‐period reversal of effects of monocular deprivation in cat striate cortex
Authors: Smith Douglas C. , Spear Peter D. , Kratz Kenneth E. 
Published: May 2005

AbstractWe reported previously that the effects of monocular deprivation on cat striate cortex cells can be partially reversed after the critical period by enucleation of the experienced eye (Kratz et al., '76). The enucleation resulted in a rapid (less than 12 hours) increase in the percent of cells which responded to the deprived eye; however, the receptive field properties of the responsive cells were abnormal. There was no change in this result if the animals were allowed to survive 3 to 16 months after the enucleation, during which the deprived eye remained closed. The present study investigated whether enucleation of the experienced eye extends the period of sensitivity during which connections from the deprived eye can be modified by visual experience. That is, we asked whether opening the deprived eye and allowing it normal visual experience after enucleation of the experienced eye would lead to a further increase in the percentage of responsive cells or produce a modification of receptive field properties.Using single‐cell recording in striate cortex, comparisons were made between monocularly deprived control kittens (MD), kittens which had the experienced eye enucleated at four months of age while the deprived eye remained closed (MD‐DE) or was opened (MD‐DE‐O) for an additional three to four months, and kittens which received reverse‐suture at the same age and for the same duration (MD‐RS). Kittens in both the MD‐DE and MD‐DE‐O groups showed an increase in the percent of cells responsive to the deprived eye compared to MD control kittens, replicating our previous findings. However, there were no differences between the MD‐DE and MD‐DE‐O groups either in terms of percent responsive cells or in the receptive field properties of those which responded. Reverse‐suture also produced a significant, although variable, increase in the percent of cells responding to the initially deprived eye. However, this increase was significantly less than that produced by enucleation of the experienced eye in MD‐DE and MD‐DE‐O animals. Among the cells responsive to the initially deprived eye in the reverse‐suture animals, the receptive field properties remained abnormal.These results suggest that binocular interactions continue to play an active role in the effects of monocular deprivation after the previously defined critical period. However, reversal procedures such as suture or enucleation of the experienced eye do not extend the period in development during which cells in striate cortex can be modified by visual experience. Rather, they may simply release those cells already receiving anatomical connections from the deprived eye from a tonic inhibition mediated by the experienced eye.