RESUMO
Vertebrate hippocampal formation is central to conversations on the comparative analysis of spatial cognition, especially in light of variation found in different vertebrate classes. Assuming the medial pallium (MP) of extant amphibians resembles the hippocampal formation (HF) of ancestral stem tetrapods, we propose that the HF of modern amniotes began with a MP characterized by a relatively undifferentiated cytoarchitecture, more direct thalamic/olfactory sensory inputs, and a more generalized role in associative learning-memory processes. As such, hippocampal evolution in amniotes, especially mammals, can be seen as progressing toward a cytoarchitecture with well-defined subdivisions, regional connectivity, and a functional specialization supporting map-like representations of space. We then summarize a growing literature on amphibian spatial cognition and its underlying brain organization. Emphasizing the MP/HF, we highlight that further research into amphibian spatial cognition would provide novel insight into the role of the HF in spatial memory processes, and their supporting neural mechanisms. A more complete reconstruction of hippocampal evolution would benefit from additional research on non-mammalian vertebrates, with amphibians being of particular interest.
Assuntos
Anfíbios , Cognição , Animais , Anfíbios/fisiologia , Cognição/fisiologia , Telencéfalo/fisiologia , Telencéfalo/anatomia & histologia , Hipocampo/fisiologia , Evolução Biológica , Percepção Espacial/fisiologiaRESUMO
Several studies on the elasmobranchs neuroanatomy have shown that their brain is more complex than previously thought, and had significant intra and interspecific variations. The objective of this work was conducting a comparative encephalic neuroanatomy study of two species of genus Myliobatis. In total, 16 organisms of genera Myliobatis californica and Myliobatis longirostris, collected in the coasts of Kino Bay, Sonora, Mexico, were used. In Myliobatis, the brain has a long telencephalon and the posterior central nucleus is poorly developed. Their cerebellum is asymmetric, has several sulci, most of which are transversally oriented, with four lobes (anterior, medium and two posterior), a condition which has not been reported for any other species. It was observed that, despite the morphology of M. californica and M. longirostris is similar, there are some significant differences. Both species have moderate foliation, but M. californica has more sulci. In the diencephalon of M. californica, it was observed that the lobes of the infundibulum are oval-shaped and separated, while in M. longirostris, such lobes are rounded and near the medium line. It has to be highlighted that Myliobatis belongs to the most derived batoid group; nevertheless, its brain is considerably less complex, as compared to what has been reported for the most derived milyobatoids species.
Diversos estudios sobre la neuroanatomía de los elasmobranquios han demostrado que el cerebro es más complejo de lo que se pensaba y presenta considerables variaciones tanto intra como interespecíficas. El objetivo de este trabajo fue realizar un estudio de neuroanatomía comparada del encéfalo de dos especies del género Myliobatis. Se utilizaron un total de 16 organismos de Myliobatis californica y Myliobatis longirostris, los cuales fueron colectados en las costas de Bahía Kino, Son., México. El cerebro de Myliobatis tiene un telencéfalo largo, el núcleo central posterior está poco desarrollado; el cerebelo es asimétrico, presenta surcos que en su mayoría están orientados transversalmente, con cuatro lóbulos (anterior, medio y dos posteriores), condición que no ha sido reportada para otra especie. Se observó que, aunque M. californica y M. longirostris presentan una morfología similar existen ciertas diferencias. En ambas especies presentan una foliación moderada; sin embargo, en M. californica se observan más surcos. En el diencéfalo de M. californica se observa que los lóbulos del infundíbulo son ovalados y están separados, mientras que en M. longirostris son redondeados y se encuentran próximos a la línea media. Es importante señalar que, pese a que Myliobatis pertenece al grupo de batoideos más derivado, su cerebro es considerablemente menos complejo de lo que se ha reportado para las especies de miliobatoideos más derivadas.
Assuntos
Animais , Rajidae/anatomia & histologia , Encéfalo/anatomia & histologia , Telencéfalo/anatomia & histologia , Cerebelo/anatomia & histologiaRESUMO
The morphological and histological structure of the brains of Bufo gargarizans and Cynops orientalis were observed by anatomy and light microscopy. The results show that the brains of Bufo gargarizans and Cynops orientalis are divided into 5 parts which include the telencephalon, diencephalon, mesencephalon, cerebellum and medulla oblongata. The telencephalon consists of the olfactory bulb and the cerebral hemisphere. The olfactory bulb is developed that has two pairs of olfactory nerve. Bufo gargarizan has a symmetrical oval hemisphere optic lobes; Cynops orientalis only has a spherical optic lobe. The cerebellum is situated behind the optic lobe and closely connected with the myelencephalon. In this paper, the morphological and histological differences between the two species are discussed. The proportion of cerebral hemisphere is gradually increasing, which correlated with a progressive increase in the number of neuronal cell classes, and reflected in behavior complexity.
La estructura morfológica e histológica de los cerebros de Bufo gargarizans y Cynops orientalis se observó mediante anatomía y microscopía óptica. Los resultados muestran que los cerebros de Bufo gargarizans y Cynops orientalis se dividen en 5 partes, que incluyen el telencéfalo, diencéfalo, mesencéfalo, cerebelo y mielencéfalo. El telencéfalo consiste en bulbo olfatorio y hemisferio cerebral. El bulbo olfatorio tiene dos pares de nervios olfatorios. Los lóbulos ópticos de Bufo gargarizans son ovalados y simétricos en ambos hemisferios cerebrales; Cynops orientalis tiene solo un lóbulo óptico esférico. El cerebelo está situado detrás del lóbulo óptico y está estrechamente conectado con el mielencéfalo. En este trabajo, se discuten las diferencias morfológicas e histológicas entre las dos especies. El tamaño del hemisferio cerebral aumenta gradualmente, lo que se correlaciona con un aumento progresivo de células neuronales en los núcleos, reflejándose en la complejidad del comportamiento.
Assuntos
Animais , Salamandridae/anatomia & histologia , Encéfalo/anatomia & histologia , Bufo bufo/anatomia & histologia , Anatomia Comparada , Telencéfalo/anatomia & histologia , Mesencéfalo/anatomia & histologia , Cerebelo/anatomia & histologia , Diencéfalo/anatomia & histologia , Mielencéfalo/anatomia & histologiaRESUMO
Teleostean fish brains are useful models to study cellular and functional specializations along the phylogenesis. The Betta splendens Regan 1910 (Siamese fighting fish; Perciformes:Anabantoidei) is known for its aggressive display, courtship behavior, nest building, and offspring care. Here, we present novel and detailed data about the cytoarchitecture of the olfactory bulb and the telencephalic hemispheres of this fish. The hematoxylin-eosin and Nissl techniques served to identify brain nuclei (n = 19 males and n = 21 females) and for the stereological evaluation of the numerical density of cells and the proportion of neurons and glial cells in the ventral telencephalon supracommissural (Vs) and postcommissural (Vp) nuclei of adult males and females. These nuclei are putative homologs of the sexually dimorphic medial amygdala in mammals. The olfactory bulb of Betta splendens consists of 5 concentrically arranged layers plus ganglion cells of the terminal nerves. The dorsal telencephalon consists of 16 different cell groups. The ventral telencephalon has 8 nuclei, plus the lateral septal organ and the nuclei of the preoptic area forming an anatomical continuum. The rostrocaudal extent of the Vs and Vp is not different between sexes. In both nuclei, the proportion of neurons to glial cells is approximately 2:1 and the density of neurons and glial cells is not different between sexes. These morphological findings can subserve future research on the brain function of the Betta splendens and the search for neural sex differences in other central areas of this same species, in other teleost species, or yet in other related vertebrate group. Anat Rec, 00:000-000, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 301:88-110, 2018. © 2017 Wiley Periodicals, Inc.
Assuntos
Mapeamento Encefálico , Perciformes/anatomia & histologia , Telencéfalo/fisiologia , Animais , Feminino , Masculino , Neuroglia/fisiologia , Neurônios/fisiologia , Fatores Sexuais , Telencéfalo/anatomia & histologia , Telencéfalo/citologiaRESUMO
The semipalmated sandpiper Calidris pusilla and the spotted sandpiper Actitis macularia are long- and short-distance migrants, respectively. C. pusilla breeds in the sub-arctic and mid-arctic tundra of Canada and Alaska and winters on the north and east coasts of South America. A. macularia breeds in a broad distribution across most of North America from the treeline to the southern United States. It winters in the southern United States, and Central and South America. The autumn migration route of C. pusilla includes a non-stop flight over the Atlantic Ocean, whereas autumn route of A. macularia is largely over land. Because of this difference in their migratory paths and the visuo-spatial recognition tasks involved, we hypothesized that hippocampal volume and neuronal and glial numbers would differ between these two species. A. macularia did not differ from C. pusilla in the total number of hippocampal neurons, but the species had a larger hippocampal formation and more hippocampal microglia. It remains to be investigated whether these differences indicate interspecies differences or neural specializations associated with different strategies of orientation and navigation.
Assuntos
Migração Animal , Charadriiformes/anatomia & histologia , Hipocampo/anatomia & histologia , Microglia/citologia , Neurônios/citologia , Animais , Cruzamento , Charadriiformes/fisiologia , Hipocampo/citologia , Imuno-Histoquímica , Tamanho do Órgão , Orientação , Fotomicrografia , Filogenia , Navegação Espacial/fisiologia , Especificidade da Espécie , Telencéfalo/anatomia & histologiaRESUMO
The semipalmated sandpiper Calidris pusilla and the spotted sandpiper Actitis macularia are long- and short-distance migrants, respectively. C. pusilla breeds in the sub-arctic and mid-arctic tundra of Canada and Alaska and winters on the north and east coasts of South America. A. macularia breeds in a broad distribution across most of North America from the treeline to the southern United States. It winters in the southern United States, and Central and South America. The autumn migration route of C. pusilla includes a non-stop flight over the Atlantic Ocean, whereas autumn route of A. macularia is largely over land. Because of this difference in their migratory paths and the visuo-spatial recognition tasks involved, we hypothesized that hippocampal volume and neuronal and glial numbers would differ between these two species. A. macularia did not differ from C. pusilla in the total number of hippocampal neurons, but the species had a larger hippocampal formation and more hippocampal microglia. It remains to be investigated whether these differences indicate interspecies differences or neural specializations associated with different strategies of orientation and navigation.
Assuntos
Animais , Migração Animal , Charadriiformes/anatomia & histologia , Hipocampo/anatomia & histologia , Microglia/citologia , Neurônios/citologia , Cruzamento , Charadriiformes/fisiologia , Hipocampo/citologia , Imuno-Histoquímica , Tamanho do Órgão , Orientação , Fotomicrografia , Filogenia , Especificidade da Espécie , Navegação Espacial/fisiologia , Telencéfalo/anatomia & histologiaRESUMO
The dorsal ventricular ridge (DVR) is one of the main components of the sauropsid pallium. In birds, the DVR is formed by an inner region, the nidopallium, and a more dorsal region, the mesopallium. The nidopallium contains discrete areas that receive auditory, visual, and multisensory collothalamic projections. These nidopallial nuclei are known to sustain reciprocal, short-range projections with their overlying mesopallial areas. Recent findings on the anatomical organization of the auditory DVR have shown that these short-range projections have a columnar organization that closely resembles that of the mammalian neocortex. However, it is unclear whether this columnar organization generalizes to other areas within the DVR. Here we examine in detail the organization of the visual DVR, performing small, circumscribed deposits of neuronal tracers as well as intracellular fillings in brain slices. We show that the visual DVR is organized in three main laminae, the thalamorecipient nucleus entopallium; a dorsally adjacent nidopallial lamina, the intermediate nidopallium; and a contiguous portion of the ventral mesopallium, the mesopallium ventrale. As in the case of the auditory DVR, we found a highly topographically organized system of reciprocal interconnections among these layers, which was formed by dorsoventrally oriented, discrete columnar bundles of axons. We conclude that the columnar organization previously demonstrated in the auditory DVR is not a unique feature but a general characteristic of the avian sensory pallium. We discuss these results in the context of a comparison between sauropsid and mammalian pallial organization.
Assuntos
Galinhas/anatomia & histologia , Neocórtex/anatomia & histologia , Telencéfalo/anatomia & histologia , Vias Visuais/anatomia & histologia , Animais , Galinhas/crescimento & desenvolvimento , Lisina/análogos & derivados , Lisina/metabolismo , Rede Nervosa/anatomia & histologia , Rede Nervosa/fisiologia , Vias Visuais/fisiologiaRESUMO
Lizards belonging to the Tropiduridae family are "sit-and-wait" foragers, relying mainly on visual identification to catch prey that cross their visual fields. Little is known about the neurobiology of Tropiduridae lizards. We have used neurohistological techniques to study the structural organization of the telencephalon of the neotropical lizard Tropidurus hispidus, paying special attention to the cerebral cortex. As revealed by the Nissl technique and Golgi staining, the telencephalon of T. hispidus follows the squamate pattern, with some differences: the lateral cortex appears relatively atrophic, and most of the neuronal somata of the dorsal cortex are dispersed without forming a conspicuous cell layer. Golgi staining has revealed ten different neuronal types in the three cortical layers, based on somata shape and dendritic morphology: the granular (unipolar, bipolar, and multipolar), pyramidal (normal, inverted, open, bipyramidal, and horizontal), spherical horizontal, and fusiform neuronal types. The axon direction could be traced in five of the subtypes. We have also studied the distribution of zinc-enriched terminals in the telencephalon of T. hispidus by the Neo-Timm method. Some portions of the cortex, septum, striatum, and amygdaloid complex stain heavily, with patterns resembling those described for other lizard families. Thus, T. hispidus appears to be an interesting representative of the Tropiduridae family for further neurobiological comparative studies.
Assuntos
Córtex Cerebral/anatomia & histologia , Lagartos/anatomia & histologia , Animais , Feminino , Masculino , Neurônios/fisiologia , Telencéfalo/anatomia & histologiaRESUMO
This paper analyzes the astroglial and neuronal responses in subtelencephalic structures, following a bilateral ablation of the telencephalon in the Columba livia pigeons. Control birds received a sham operation. Four months later the birds were sacrificed and their brains processed for glial fibrillary acid protein (GFAP) and neurofilament immunohistochemistry, markers for astrocytes and neurons, respectively. Computer-assisted image analysis was employed for quantification of the immunoreactive labeling in the nucleus rotundus (N.Rt) and the optic tectum (OT) of the birds. An increased number of GFAP immunoreactive astrocytes were found in several subregions of the N.Rt (p< .001), as well as in layers 1, 2cd, 3, and 6 of the OT (p< .001) of the lesioned animals. Neurofilament immunoreactivity decreased massively in the entire N.Rt of the lesioned birds; however, remaining neurons with healthy aspect showing large cytoplasm and ramified branches were detected mainly in the periphery of the nucleus. In view of the recently described paracrine neurotrophic properties of the activated astrocytes, the data of the present study may suggest a long-lasting neuroglial interaction in regions of the lesioned bird brain far from injury. Such events may trigger neuronal plasticity in remaining brain structures that may lead spontaneous behavior recovery as the one promoted here even after a massive injury.
Assuntos
Astrócitos/metabolismo , Columbidae/fisiologia , Gliose/fisiopatologia , Plasticidade Neuronal/fisiologia , Telencéfalo/fisiologia , Vias Visuais/fisiologia , Animais , Astrócitos/citologia , Biomarcadores/análise , Biomarcadores/metabolismo , Mapeamento Encefálico , Columbidae/anatomia & histologia , Denervação , Proteína Glial Fibrilar Ácida/análise , Proteína Glial Fibrilar Ácida/metabolismo , Gliose/metabolismo , Gliose/patologia , Citometria por Imagem , Imuno-Histoquímica , Masculino , Proteínas de Neurofilamentos/análise , Proteínas de Neurofilamentos/metabolismo , Neurônios/citologia , Neurônios/metabolismo , Especificidade da Espécie , Coloração e Rotulagem , Colículos Superiores/anatomia & histologia , Colículos Superiores/fisiologia , Telencéfalo/anatomia & histologia , Tálamo/anatomia & histologia , Tálamo/fisiologia , Fatores de Tempo , Vias Visuais/anatomia & histologiaRESUMO
Evaluamos las repercusiones de la desnutrición y/o de la manipulación serotoninérgica, durante el período de crecimiento rápido del encéfalo, en el desarrollo somático en ratas. Para esto, fue utilizado el protocolo de medidas de indicadores de desarrollo propuesto por Silva et al., 2005. El protocolo fue aplicado del 1er al 21 día. Las ratas fueron amamantadas por madres que recibieron dieta controlada (dieta comercial, Labina) normoproteica con 23 por ciento de proteínas (Grupo Nutrido - Nut), n=15, o fueron amamantados por madres que después del parto recibieron dieta hipoprotéica (Dieta Básica Regional DBR), conteniendo 8 por ciento de proteína (Grupo Desnutrido - Desn), n=15. En el grupo desnutrido fueron observadas reducciones en el peso corporal a partir del 4 día, en el eje látero-lateral del cráneo del 8° al 21° día de vida, en el eje ántero-posterior del cráneo del 10° al 21° día, en el eje longitudinal y en la cola del 7° al 21° día (p = 0.05). El estudio ratificó la hipótesis que la desnutrición, en el período crítico del desarrollo, interviene con el crecimiento somático de las ratas. Por otra parte, fue comprobado que el uso de protocolos con la definición de puntos anatómicos y precisión de las medidas, proporcionan una uniformidad en los períodos en que son observados los efectos deletéreos estudiados.
This study analyzed the consequence of malnutrition and/or serotoninergic manipulation during the period of fast growth of encephalon on the somatic development in rats. It was used the protocol of measurement of indicators of this development proposed by Silva et al., 2005. The protocol was applied from 1st to 21st day and rats were breastfed by female which received control diet (commercial diet, Labina) with 23% of protein, normoproteic diet, nourished animals (Group Nourished Nour), n=15 or were breastfed by female which after the delivery received hypoproteic diet (Regional Basic Diet RBD), with 8% of protein, malnourished animals (Group Malnourished Maln) n=15. It were observed in the group malnourished a decrease of corporal weight from 4th day, of latero-lateral axis of skull from 8th to 21st day, of antero-posterior axis of skull from 10th to 21st day, of longitudinal axis and length of tail from 7th to 21st day of life (p 0,05) The study emphasized the hypothesis that malnutrition in critical period of development, interferes on somatic development of rats. Besides that, it was emphasized that the use of protocols with definition of anatomic points and suitable choice of material and accuracy of measurements provide a higher uniformity in periods which were observed the deleterious effects in all studied axes.
Assuntos
Animais , Masculino , Feminino , Lactente , Ratos , Telencéfalo/anatomia & histologia , Telencéfalo/crescimento & desenvolvimento , Transtornos da Nutrição do Lactente/veterinária , Guias como Assunto , Ratos Wistar/crescimento & desenvolvimento , Transtornos Somatoformes/induzido quimicamente , Transtornos Somatoformes/terapiaRESUMO
We analyzed operant discrimination in detelencephalated pigeons and neuroanatomical substrates after long-term detelencephalation. In Experiment I, experimental pigeons with massive telencephalic ablation and control pigeons were conditioned to key peck for food. Successive discrimination was made under alternating red (variable-ratio reinforcement) and yellow (extinction) lights in one key of the chamber. These relations were interchanged during reversal discrimination. The sessions were run until steady-state rates were achieved. Experiment II analyzed the morphology of the nucleus rotundus and optic tectum in long-term detelencephalated and control birds, using a Klüver-Barrera staining and image analyzer system. Detelencephalated birds had more training sessions for response shaping and steady-state behavior (p < 0.001), higher red key peck rates during discrimination (p < 0.01), and reversal discrimination indexes around 0.50. Morphometric analysis revealed a decreased number of neurons and increased vascularity, associated with increases in the perimeter (p < 0.001) in the nucleus rotundus. In the optic tectum, increases in the perimeter (p < 0.05) associated with disorganization in the layers arrangement were seen. The data indicate that telencephalic systems might have an essential function in reversal operant discrimination learning. The structural characteristics of subtelencephalic systems after long-term detelencephalation evidence plastic changes that might be related to functional mechanisms of learning and neural plasticity in pigeons.
Assuntos
Condicionamento Operante/fisiologia , Aprendizagem por Discriminação/fisiologia , Plasticidade Neuronal/fisiologia , Telencéfalo/fisiologia , Animais , Contagem de Células , Circulação Cerebrovascular/fisiologia , Columbidae , Interpretação de Imagem Assistida por Computador , Neurônios/fisiologia , Colículos Superiores/fisiologia , Telencéfalo/anatomia & histologiaAssuntos
Apoptose/efeitos dos fármacos , Inseticidas/toxicidade , Piretrinas/toxicidade , Telencéfalo/citologia , Animais , Anuros , Larva , Dose Letal Mediana , Microscopia Eletrônica , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/ultraestrutura , Ribossomos/efeitos dos fármacos , Ribossomos/ultraestrutura , Análise de Sobrevida , Telencéfalo/anatomia & histologia , Telencéfalo/efeitos dos fármacos , Fatores de TempoRESUMO
En los estudios de neurología experimental se ha evitado, en general, utilizar al perro, a pesar que esta especie es una de las favoritas para la fisiología experimental. Esta situación se debe en parte a la variabilidad en la morfometría de su cráneo, pero la causa fundamental es que la investigación se ha realizado en otras especies en las que la anatomía del encéfalo es mejor conocida. Los trabajos de Lim, Liu y Moffit demostraron que la variabilidad de las cabezas de los perros no era necesariamente un obstáculo, y aplicaron en los caninos la técnica estereotáxica de Horsley y Clarke. A partir de tales estudios, se multiplicaron las posibilidades en la investigación de la neuroanatomía del perro. No obstante, la cantidad y calidad de información respecto al encéfalo de los caninos que ha generado este impulso en la neurofisiología y la neurología experimental, no ha encontrado su contraparte en la neuroanatomía, situación que genera una disociación del conocimiento, al punto de trabajar con distintas nomenclaturas y denominaciones. En este trabajo se ha intentado, con un criterio fundamentalmente anatómico, conjugar las descripciones macroscópicas del cerebro de los caninos con las descripciones citoarquitectónicas, así como también, con los hallazgos funcionales, para que la neuroanatomía sea la base de la pirámide del conocimiento en el que se sustenta la neurofisiología y la neurología aplicada
Assuntos
Animais , Gatos , Cães , Cérebro/anatomia & histologia , Cães/anatomia & histologia , Carnívoros/anatomia & histologia , Córtex Cerebral/anatomia & histologia , Neocórtex/anatomia & histologia , Primatas/anatomia & histologia , Telencéfalo/anatomia & histologiaRESUMO
The diencephalic preglomerular complex of gymnotiform fish receives inputs from several sensory areas. By employing anterograde and retrograde tracing techniques, we studied the afferent and efferent connections of the dorsolateral area (dorsal subdivision) of the telencephalon with the preglomerular nuclei in the weakly electric fish, Gymnotus carapo. Neurons of the medial preglomerular nucleus project to intermediate and deep portions of the middle (commissural) level of the dorsolateral telencephalon, and neurons located in the lateral preglomerular nucleus project to superficial portions of the middle levels of the dorsolateral telencephalon. Therefore, we observed a spatial distribution pattern of connectivity between dorsolateral telencephalon and preglomerular complex.
Assuntos
Diencéfalo/fisiologia , Peixe Elétrico/fisiologia , Vias Neurais/fisiologia , Telencéfalo/fisiologia , Animais , Biotina/análogos & derivados , Dextranos , Diencéfalo/anatomia & histologia , Diencéfalo/citologia , Corantes Fluorescentes , Vias Neurais/anatomia & histologia , Neurônios/fisiologia , Telencéfalo/anatomia & histologia , Telencéfalo/citologiaRESUMO
A restraining box for the head and body of the electric fish Gymnotus carapo was constructed and coupled to a micromanipulator, permitting us to prepare an atlas of the telencephalon with stereotaxic parameters. A photograph and a schematic drawing of an animal's head is presented, showing two skin electroreceptors that were used as external landmarks. A sagittal section of the telencephalic structure is also presented, whose vertical bars indicate the frontal planes that compose the atlas. The frontal planes of the atlas consist of serial sections spaced 600 or 500 microns apart in the rostrocaudal axis. Sections mapped with acetylcholinesterase are shown, intercalated with Nissl-stained sections. The acetylcholinesterase sections proved to be useful for the delimitation of certain nuclei and for the exact localization of small fissures and fiber tracts. A brief description of major cytoarchitectural subdivision and connections of the telencephalon is provided.
Assuntos
Peixe Elétrico/anatomia & histologia , Telencéfalo/anatomia & histologia , Acetilcolinesterase/análise , Animais , Corantes , Fotografação/métodos , Técnicas Estereotáxicas , Telencéfalo/citologia , Telencéfalo/enzimologiaRESUMO
Biotinylated dextran amine was injected unilaterally into dorsal regions of the telencephalon of the weakly electric fish Gymnotus carapo in order to study the afferent and efferent connections of specific dorsal regions with ventral regions of the telencephalon and with other regions of the central nervous system. Efferent pathways from the dorsolateral area of the telencephalon project ipsilaterally to the anterior hypothalamic nucleus, the ventral thalamus and magnocellular tegmental nucleus, whose axons reach the spinal cord. Anterograde labeling showed that the central division of the dorsal telencephalon sends efferent projections through the lateral forebrain bundle towards the ipsilateral lateral and medial preglomerular nucleus, the pretectal nucleus, the optic tectum and the dorsal torus semicircularis, regions that are all involved in the processing of electrosensory and/or multisensory information. In addition, when biotinylated dextran amine was injected into the dorsal torus semicircularis, retrogradely labeled neurons were observed in the dorsocentral area of the telencephalon. The dorsocentral area is also a target of the extra-telencephalic afferents originating from rostral, lateral and medial regions of preglomerular complex. Within the telencephalon, neurons of many ventral subdivisions project ipsilaterally to the dorsocentral area. The dorsocentral, dorsolateral and dorsomedial areas are connected ipsilaterally and reciprocally. The dorsocentral area is reciprocally connected with its contralateral homologue through the anterior commissure.
Assuntos
Peixe Elétrico/anatomia & histologia , Células Receptoras Sensoriais/anatomia & histologia , Telencéfalo/anatomia & histologia , Vias Aferentes/anatomia & histologia , Animais , Mapeamento Encefálico , Dominância Cerebral/fisiologia , Vias Eferentes/anatomia & histologia , Neurônios/ultraestrutura , Medula Espinal/anatomia & histologiaRESUMO
To test the hypothesis that selection for spatial abilities which require birds to locate and to return accurately to host nests has produced an enlarged hippocampus in brood parasites, three species of cowbird were compared. In shiny cowbirds, females search for host nests without the assistance of the male; in screaming cowbirds, males and females inspect hosts' nests together; in bay-winged cowbirds, neither sex searches because this species is not a brood parasite. As predicted, the two parasitic species had a relatively larger hippocampus than the non-parasitic species. There were no sex differences in relative hippocampus size in screaming or bay-winged cowbirds, but female shiny cowbirds had a larger hippocampus than the male.
Assuntos
Aves/fisiologia , Hipocampo/anatomia & histologia , Comportamento de Nidação/fisiologia , Animais , Feminino , Masculino , Caracteres Sexuais , Especificidade da Espécie , Telencéfalo/anatomia & histologiaRESUMO
The reptilian brain is characterized by a structure that bulges into the lateral ventricle, called dorsal ventricular ridge (DVR). The DVR was originally considered to be a part of the basal ganglia, although more recent studies indicate that it may correspond to the dorsal part of the hemisphere. The anterior portion of the DVR has several connectional and functional similarities with parts of the mammalian neocortex, for which reason it has been claimed that the two structures can be considered as homologues. In this article I review the evidence supporting and refuting homology of the DVR with different telencephalic structures of mammals, concluding that it is still early to unequivocally ascribe structural correspondences between the different components in the two vertebrate classes. However, a way out of the problem is suggested by comparing the embryonic position of DVR with that of lateral cortex in the reptilian hemisphere. The lateral cortex is considered to be quite comparable in reptiles and mammals, and hence may be a good marker for the original position of the DVR. If the DVR originates dorsal to lateral cortex, it may be considered comparable to parts of the mammalian neocortex, while if it develops in its same position or ventral to it, it may not correspond to the neocortex. Early embryological work indicated that the DVR develops in the same position as the lateral cortex, but arises as a late migration wave, after cells destined to lateral cortex are generated. In other words, instead of being interposed between dorsal and lateral cortices, the DVR may originate in a position overlapping with lateral cortex. If this alternative turns out to be the case, it may imply that the DVR arose de novo, through an extension of the ancestral period of neuroblast proliferation. As a consequence, there may be no structures comparable to it in other vertebrate classes. Finally, it is also proposed that, regardless of whether the DVR and the extrastriate neocortex can or cannot be considered phylogenetic homologues, some of the integrative functions performed by them might have a common evolutionary origin, that became localized in the reptilian DVR and in the mammalian extrastriate neocortex.
Assuntos
Encéfalo/fisiologia , Répteis/fisiologia , Animais , Encéfalo/anatomia & histologia , Córtex Cerebral/anatomia & histologia , Córtex Cerebral/fisiologia , Ventrículos Cerebrais/anatomia & histologia , Ventrículos Cerebrais/fisiologia , Répteis/embriologia , Telencéfalo/anatomia & histologia , Telencéfalo/fisiologiaRESUMO
The reptilian brain is characterized by a structure that bulges into the lateral ventricle, called dorsal ventricular ridge (DVR). The DVR was originally considered to be a part of the basal ganglia, although more recent studies indicate that it may correspond to the dorsal part of the hemisphere. The anterior portion of the DVR has several connectional and functional similarities with parts of the mammalian neocortex, for which reason it has been claimed that the two structures can be considered as homologues. In this article I review the evidence supporting and refuting homology of the DVR with different telencephalic structures of mammals, concluding that it is still early to unequivocally ascribe structural correspondences between the different components in the two vertebrate classes. However, a way out of the problem is suggested by comparing the embryonic position of DVR with that of lateral cortex in the reptilian hemisphere. The lateral cortex is considered to be quite comparable in reptiles and mammals, and hence may be a good marker for the original position of the DVR. If the DVR originates dorsal to lateral cortex, it may be considered comparable to parts of the mammalian neocortex, while if it develops in its same position or ventral to it, it may not correspond to the neocortex. Early embryological work indicated that the DVR develops in the same position as the lateral cortex, but arises as a late migration wave, after cells destined to lateral cortex are generated. In other words, instead of being interposed between dorsal and lateral cortices, the DVR may originate in a position overlapping with lateral cortex. If this alternative turns out to be the case, it may imply that the DVR arose de novo, through an extension of the ancestral period of neuroblast proliferation. As a consequence, there may be no structures comparable to it in other vertebrate classes. Finally, it is also proposed that, regardless of whether the DVR and the extrastriate neocortex can or cannot be considered phylogenetic homologues, some of the integrative functions performed by them might have a common evolutionary origin, that became localized in the reptilian DVR and in the mammalian extrastriate neocortex
Assuntos
Animais , Encéfalo/fisiologia , Répteis/fisiologia , Encéfalo/anatomia & histologia , Córtex Cerebral/anatomia & histologia , Córtex Cerebral/fisiologia , Ventrículos Cerebrais/anatomia & histologia , Ventrículos Cerebrais/fisiologia , Répteis/embriologia , Telencéfalo/anatomia & histologia , Telencéfalo/fisiologiaRESUMO
Relative olfactory bulb size with respect to telencephalic hemispheres (olfactory ratio) was measured in five species of hummingbirds. Trochiliformes were found to be next to last among 25 avian orders with respect to olfactory bulb development. One hummingbird species, the White-vented Violetear (Colibri serrirostris), was trained in a successive go/no-go discrimination task, and learned to feed or not to feed from a container dependent on the olfactory stimuli associated with it. Test birds learned to discriminate amyl acetate vs. turpentine essence, jasmine essence vs. lavender essence, eucalyptus essence vs. no odor, beta-ionone vs. no odor, carvone vs. eucalyptol. In contrast, 1-phenylethanol vs. beta-ionone discrimination, two odorants which appear similar to humans, was unsuccessful. Using a similar procedure, attempts were made to condition a White-vented Violetear and a Versicolored Emerald (Amazilia versicolor) to magnetic stimuli. The birds were unable to discriminate between a normal field and an oscillating field (square wave, 1 Hz, amplitude +/- 0.40 G).