The dorsal and medial pallial formations of mammals, birds, and reptiles show overall functional striking similarities. Most of these similarities have been frequently considered examples of convergent evolution. However, a considerable amount of neurobiological comparative evidence suggests the presence of a common basic pattern of vertebrate forebrain organization. This common pattern can support functional conservation.

The isocortex is a distinctive feature of mammalian brains, which has no clear counterpart in the cerebral hemispheres of other amniotes. This paper speculates on the evolutionary processes giving rise to the isocortex. As a first step, we intend to identify what structure may be ancestral to the isocortex in the reptilian brain. Then, it is necessary to account for the transformations (developmental, connectional, and functional) of this ancestral structure, which resulted in the origin of the isocortex. One long-held perspective (...) argues that part of the isocortex derives from the ventral pallium of reptiles, whereas another view proposes that the isocortex originated mostly from the dorsal pallium. We consider that, at this point, evidence tends to favor correspondence of the isocortex with the dorsal cortex of reptiles. In any case, the isocortex may have originated partly as a consequence of an overall “dorsalizing” effect (that is, an expansion of the territories expressing dorsal-specific genes) during pallial development. Furthermore, expansion of the dorsal pallium may have been driven by selective pressures favoring the development of associative networks between the dorsal cortex, the olfactory cortex, and the hippocampus, which participated in spatial or episodic memory in the early mammals. In this context, sensory projections that in reptiles end in the ventral pallium, are observed to terminate in the isocortex (dorsal pallium) of mammals, perhaps owing to their participation in these associative networks. Key Words: basolateral amygdala; claustrum; Emx-1; endopiriform nucleus; dorsal cortex; dorsal ventricular ridge; hippocampus; homology; olfactory cortex; Pax-6; ventral pallium. (shrink)

: In this paper I argue that Velmens’ reflexive model of perceptual consciousness is useful for understanding the first-person perspective and sentience in animals. I then offer a defense of the proposal that ray-finned bony fish have a first-person perspective and sentience. This defense has two prongs. The first prong is presence of a substantial body of evidence that the neuroanatomy of the fish brain exhibits basic organizational principles associated with consciousness in mammals. These principles include a relationship between a (...) second-order sensory relay, the preglomerular complex, and the fish pallium which bears a resemblance to the relationship between the mammalian thalamus and the neocortex, the existence of feedback/feedforward and reentrant circuitry in the pallium, and structural and functional differences among divisions of the fish pallium. The second prong is the existence of behaviors in fish that exhibit significant flexibility in the presence of environmental change and require relational learning among stimuli distributed in space, over time, or both. I conclude that, although they are instantiated differently, a first-person perspective and sentience are present in fish. Resumo: Neste artigo, argumento que o modelo reflexivo de consciência perceptiva de Velmans é útil para se entender a perspectiva de primeira pessoa e a sentiência em animais. Em seguida, ofereço uma defesa da proposta de que os peixes ósseos com nadadeiras raiadas tenham sentiência e perspectiva de primeira pessoa. Esta defesa tem dois momentos. O primeiro ponto é a presença de um corpo substancial de evidências de que a neuroanatomia do cérebro de peixes exibe os princípios organizacionais básicos associados à consciência em mamíferos. Esses princípios incluem a interação entre um relê sensorial de segunda ordem e o pálio, os quais apresentam, respectivamente, estreita semelhança com o tálamo e o neocórtex dos mamíferos; a existência de circuitos de retroalimentação e reentrada, assim como diferenças estruturais e funcionais entre as divisões do pálio. A segunda questão é a existência de comportamentos de peixes que exibem flexibilidade significativa na presença de mudanças ambientais e requerem aprendizado relacional entre estímulos distribuídos no espaço, ao longo do tempo, ou ambos. Concluo que, embora sejam instanciados de maneira diferente dos mamíferos, uma perspectiva de primeira pessoa e sentiência estão presentes nos peixes. (shrink)

Video barbam et pallium, philosophum nondum videoAulo Gellio, Noctes Atticae, IX, 2, 4 1 Lo scenario Immaginiamo che il direttore di un grande museo venga a sapere che uno dei più grandi e riconosciuti maestri dell’arte contemporanea - anch’egli immaginario, chiamiamolo per comodità D’Auchan — ha lasciato in eredità a qualcuno, diciamo un oscuro collezionista, una grande quantità di opere del tutto inedite e completamente ignote anche alla critica, che il fortunato beneficiario ha deciso infi...

After reviewing the literature on current knowledge about consciousness in humans, we present a state-of-the art discussion on consciousness and related key concepts in animals. Obviously much fewer publications are available on non-human species than on humans, most of them relating to laboratory or wild animal species, and only few to livestock species. Human consciousness is by definition subjective and private. Animal consciousness is usually assessed through behavioural performance. Behaviour involves a wide array of cognitive processes that have to be (...) assessed separately using specific experimental protocols. Accordingly, several processes indicative of the presence of consciousness are discussed: perception and cognition, awareness of the bodily-self, self-related knowledge of the environment (including social environment). When available, specific examples are given in livestock species. Next, we review the existing evidence regarding neuronal correlates of consciousness, and emphasize the difficulty of linking aspects of consciousness to specific neural structures across the phyla because high-level cognitive abilities may have evolved independently along evolution. Several mammalian brain structures (cortex and midbrain) are involved in the manifestations of consciousness, while the equivalent functional structures for birds and fishes would likely be the pallium/tectum and midbrain. Caution is required before excluding consciousness in species not having the same brain structures as the mammalian ones as different neural architectures may mediate comparable processes. Finally, specific neurophysiological mechanisms appear to be strongly linked to the emergence of consciousness, namely neural synchrony and neural feedback. Considering the limited amount of data available and the few animal species studied so far, we conclude that different manifestations of consciousness can be observed in animals but that further refinement is still needed to characterize their level and content in each species. Further research is required to clarify these issues, especially in livestock species. (shrink)

A dorsalization mechanism is a good candidate for the evolutionary origin of the isocortex, producing a radial and tangential expansion of the dorsal pallium (and perhaps other structures that acquired a cortical phenotype). Evidence suggests that a large part of the dorsal ventricular ridge (DVR) of reptiles and birds derives from the embryonic ventral pallium, whereas the isocortex possibly derives mostly from the dorsal pallium. In early mammals, the development of olfactory-hippocampal associative networks may have been pivotal (...) in facilitating the selection of a larger and more complex dorsal pallium which received both collothalamic and lemnothalamic sensory information. Finally, although it is not clear exactly when mammalian brain expansion began, fossil evidence indicates that this was a late event in mammaliaform evolution. (shrink)

One hypothesis of isocortical evolution requires tangential migration of glutaminergic neurons. A second requires invasion of collothalamic afferents into the dorsal pallium, a territory that in sauropsids is solely lemnopallial. A third alternative is noted here – duplication of the original collopallial territory. The duplicated region would be formed by radial migration of excitatory neurons and would maintain its collothalamic innervation.

The origin of the isocortex may be seen as a series of gradual changes (each one with an adaptive value) from a reptilian-like cerebral cortex, as proposed by Aboitiz et al., or as a new dorsal pallium derivative in mammals which undergoes a surface expansion concomitant with the expansion of the dorsal tier of the dorsal thalamus.

A rigorous cladistic analysis of the dorsal pallium of amniotes indicates that the stem amniote lacked sensorimotor areas. Reptiles apparently acquired a visual cortex by parcellation from the multimodal, hippocampal-like mediodorsal pallium of stem amniotes. The high number of sensory areas of the mammalian isocortex might derive from the specific properties it shows, such as growth-promoting influence on thalamic axons.

An alteration in the developmental mechanisms that regulate telencephalic patterning or pallial growth may have led to an enlargement of the dorsal pallium during evolution, and to the origin of isocortex. Developmental mechanisms that may have produced a pallial enlargement, and the parallelism of this event with the enlargement of the dorsal thalamus during evolution are discussed.

Most parts of the brain are conserved across reptiles and birds (sauropsids) and mammals. Two major qualitative differences occur in the upper part, or pallium, of the telencephalon, the most rostral part of the brain. Mammals have a six‐layered neocortex and also exhibit a different morphological organization in the lateral half, or sector, of their pallium than do sauropsids. These differences of lateral pallial construction may derive from small but crucial differences in migration patterns of neuronal precursors generated (...) at or above the corner of the lateral ventricle, the corticostriatal junction (CS). Sauropsids have a large structure, the dorsal ventricular ridge, that is proliferated from this region, and its anterior part (ADVR) receives ascending projections from the dorsal thalamus. Mammals have multiple structures in this same region—the lateral part of neocortex, amygdala, and claustrum‐endopiriform formation. We propose here that, as the degree of development of structures that form the deeper tier of the pallium varies across the stages of embryology and across phylogeny, mutations may have occurred during evolution at the origin of mammals that had profound consequences for the fate of neural populations generated in the region of the CS and its neighboring pallial germinal zone. BioEssays 24:530–541, 2002. © 2002 Wiley Periodicals, Inc. (shrink)

The target article about the origin and evolution of the isocortex triggers questions about unresolved issues that still need to be dealt with, including: (1) the evolutionary scenario of the origin of the lateral isocortex, (2) the expansion of the dorsal pallium in nonmammals, and (3) the heterogeneity of the anterior dorsal ventricular ridge.

Phenomenal consciousness or the subjective experience of feeling sensory stimuli is fundamental to human existence. Because of the ubiquity of their subjective experiences, humans seem to readily accept the anthropomorphic extension of these mental states to other animals. Humans will typically extrapolate feelings of pain to animals if they respond physiologically and behaviourally to noxious stimuli. The alternative view that fish instead respond to noxious stimuli reflexly and with a limited behavioural repertoire is defended within the context of our current (...) understanding of the neuroanatomy and neurophysiology of mental states. Consequently, a set of fundamental properties of neural tissue necessary for feeling pain or experiencing affective states in vertebrates is proposed. While mammals and birds possess the prerequisite neural architecture for phenomenal consciousness, it is concluded that fish lack these essential characteristics and hence do not feel pain. (shrink)

Even if legal texts and practices of the Republican and Imperial Rome establish a ranking between the clothes by status (free/not free), sex and age, some appear as unisex clothing; moreover, that is the way to wear them (habitus), plus gestures (gestus) and walk (incessus) that give them their masculine or feminine connotations. The meaning of the garment is constructed by a system of oppositions (toga pura VS toga praetexta : stola VS toga, etc.) operating only in context. Thus, the (...) garment can characterize both a status, a rank (magistratus/not magistratus) and state (mournin citizen, teenager doing his tirociunim, bride…), much more than gender. In addition, since clothing and ways to wear them are strictly regulated, transgressions or deviations from this code are always meaningful, being the object of the gaze and comments of the society members. (shrink)