En este ensayo proponemos que el mecanismo ha originado la diversidad de seres vivos encontramos hoy dia, y tambien a biosfera como un sistema coherente autonomos e interrelacionados, es deriva natural. Y aquello los biologos connotamos con expresion seleccion natural, una consecuencia historia constitucion por medio no genera esta historia. Ademas, en desarrollo estas nociones, proponemos: a) Tierra del surgimiento, conservacion diversificacion linajes, poblaciones; b) reproduccion...

The tectofugal pathway is a massive ascending polysynaptic from the tectum to thalamus and then telencephalon. In birds, initial component of this known as tectorotundal pathway; in mammals, it tectopulvinar pathway. avian highly developed; thus, provides particularly appropriate model for exploring fundamental properties system all amniotes. To further define connectivity projections pathway, we injected cholera toxin B fragment into various rotundal divisions, tectobulbar projection,...

We describe the operation of a midbrain neural circuit in pigeons that may participate selecting and attending to one visual stimulus from myriad displayed their environment. This mechanism is based on topographically organized cholinergic signal reentering optic tectum (TeO). have shown previously that, whenever activates neurons given tectal location, this location receives strong bursting feedback nucleus isthmi pars parvocellularis (Ipc), situated underneath tectum. Here we show if...

The avian nucleus rotundus, a that appears to be homologous the inferior/ caudal pulvinar of mammals, is major target an ascending retino-tecto-thalamic pathway. Further clarification inputs rotundus and their functional properties will contribute our understanding fundamental role tectal telencephalon in all vertebrates, including mammals. We found contains massive plexus glutamic acid decarboxylase (GAD)-immunoreactive axons using antibodies against GAD. cells within however, were not...

When a salient object in the visual field captures attention, neural representation of that is enhanced at expense competing stimuli. How activity evoked by stimulus evolves to take precedence over other stimuli matter intensive investigation. Here, we describe pigeons ( Columba livia ) how retinal inputs optic tectum (TeO, superior colliculus mammals), triggered moving stimuli, are selectively relayed on rotundus (Rt, caudal pulvinar) thalamus, and its pallial target, entopallium (E,...

ABSTRACT The dorsal ventricular ridge (DVR) is one of the main components sauropsid pallium. In birds, DVR formed by an inner region, nidopallium, and a more mesopallium. nidopallium contains discrete areas that receive auditory, visual, multisensory collothalamic projections. These nidopallial nuclei are known to sustain reciprocal, short‐range projections with their overlying mesopallial areas. Recent findings on anatomical organization auditory have shown these columnar closely resembles...

Abstract The retinotectofugal system is the main visual pathway projecting upon telencephalon in birds and many other nonmammalian vertebrates. ascending tectal projection arises exclusively from cells located layer 13 of optic tectum directed bilaterally toward thalamic nucleus rotundus. Although previous studies provided evidence that different types project to subdivisions Rt, apparently without maintaining a retinotopic organization, detailed spatial organization this remains obscure. We...

Abstract The sensory–motor division of the avian arcopallium receives parallel inputs from primary and high‐order pallial areas sensory vocal control pathways, sends a prominent descending projection to ascending premotor, subpallial stages these pathways. While this organization is well established for auditory trigeminal systems, arcopallial subdivision related tectofugal visual system its optic tectum (TeO) has been less investigated. In study, we charted area displaying responses by...

The parabigeminal nucleus (PBG) is the mammalian homologue to isthmic complex of other vertebrates. Optogenetic stimulation PBG induces freezing and escape in mice, a result thought be caused by projection central amygdala. However, complex, including PBG, has been classically considered satellite nuclei Superior Colliculus (SC), which upon its medial part also triggers fear avoidance reactions. As PBG-SC connectivity not well characterized, we investigated whether topology SC could related...

Most birds have an opposable digit 1 (hallux) allowing the foot to grasp, which evolved from non-opposable hallux of early theropod dinosaurs. An important morphological difference with theropods is twisting long axis its metatarsal. Here, we show how embryonic musculature and onset activity are required for metatarsal (Mt1) retroversion hallux. Pharmacologically paralyzed embryos do not fully retrovert a straight Mt1 shaft, phenocopying morphology tetanuran Molecular markers cartilage...

The mammalian pulvinar complex is a collection of dorsal thalamic nuclei related to several visual and integrative processes. Previous studies have shown that the superficial layers superior colliculus project multiple divisions complex. Although most these works agree about existence an ipsilateral tectopulvinar projection arising from stratum griseum superficialis, some others report bilateral originating this same tectal layer. We investigated organization projections in Californian...

SUMMARY It has been argued that trichromatic bees with photoreceptor spectral sensitivity peaks in the ultraviolet (UV), blue and green areas of spectrum are blind to long wavelengths (red humans). South American temperate forests (SATF) contain a large number human red-looking flowers reported be visited by bumblebee Bombus dahlbomii. In present study, B. dahlbomii's was measured through electroretinogram (ERG) recordings. No extended found The reflectance curves from eight plant species...

In mammals, social and sexual behaviours are largely mediated by the vomeronasal system (VNS). The accessory olfactory bulb (AOB) is first synaptic locus of VNS ranges from very large in Caviomorph rodents, small carnivores ungulates, to its complete absence apes, elephants, most bats aquatic species. Two pathways have been described mammals. mice, neurons expressing Gαi2 protein project rostral portion AOB respond mostly volatile molecules, whereas Gαo caudal non-volatile molecules....

In scatter-hoarding species, several behavioral and neuroanatomical adaptations allow them to store retrieve thousands of food items per year. Nectarivorous animals face a similar scenario having remember quality, location replenishment schedules nectar sources. the green-backed firecrown hummingbird (Sephanoides sephanoides), males are territorial have ability accurately keep track characteristics their defended contrast, females display an opportunistic strategy, performing rapid...

Binocular vision is a visual property that allows fine discrimination of in-depth distance (stereopsis), as well enhanced light and contrast sensitivity. In mammals binocular structurally associated with large degree frontal overlap, the presence corresponding retinal specialization containing fovea or an area centralis, well-developed ipsilateral projections to lateral thalamus (GLd). We compared these traits in two visually active species genus Octodon exhibit contrasting habits: diurnal...

Abstract The anklebone (astragalus) of dinosaurs presents a characteristic upward projection, the ‘ascending process’ (ASC). ASC is present in modern birds, but develops separate ossification centre, and projects from calcaneum most species. These differences have been argued to make it non-comparable dinosaurs. We studied development six different orders birds using traditional techniques spin–disc microscopy for whole-mount immunofluorescence. Unexpectedly, we found derives embryonic...

The tectofugal pathway (retina--optic tectum--nucleus rotundus--entopallium) is a prominent route mediating visual discrimination in diurnal birds. Several lines of evidence have shown that at the tecto-rotundal stage this composed multiple parallel channels. Anatomical studies show nucleus rotundus least four subdivisions, according to differences cytoarchitectonic, histochemical, and hodological properties. Each these subdivisions receipt highly convergent, nontopographic tectal...

The isthmic complex is part of a visual midbrain circuit thought to be involved in stimulus selection and spatial attention. In birds, this composed the nuclei isthmi pars magnocellularis (Imc), parvocellularis (Ipc), semilunaris (SLu), all them reciprocally connected ipsilateral optic tectum (TeO). Imc conveys heterotopic inhibition TeO, Ipc, SLu via widespread γ-aminobutyric acid (GABA)ergic axons that allow global competitive interactions among simultaneous sensory inputs. Anatomical...

Owen’s pre-evolutionary definition of a homologue as “the same organ in different animals under every variety form and function” its redefinition after Darwin trait lineages due to common ancestry” entail the heuristic problem: how establish “sameness”. Although criteria for homology often conflict, there is currently generalized acceptance gene expression best criterion. This gene-centered view results from reductionist preformationist concept living beings. Here, we adopt an alternative...