A behaviorally related developmental switch in nitrergic modulation of locomotor rhythmogenesis in larval Xenopus tadpoles

Supported by PICS (Projet International de Coopération Scientifique) of the French CNRS and a LabEx BRAIN Visiting Professorship to KTS. SPC was a BBSRC research student. NWS was an MPhil student supported in part by the E & RS Research Fund of the University of St Andrews.Locomotor control requires functional flexibility to support an animal's full behavioral repertoire. This flexibility is partly endowed by neuromodulators, allowing neural networks to generate a range of motor output configurations. In hatchling Xenopus tadpoles, before the onset of free-swimming behavior, the gaseous modulator nitric oxide (NO) inhibits locomotor output, shortening swim episodes and decreasing swim cycle frequency. While populations of nitrergic neurons are already present in the tadpole's brain stem at hatching, neurons positive for the NO-synthetic enzyme, NO synthase, subsequently appear in the spinal cord, suggesting additional as yet unidentified roles for NO during larval development. Here, we first describe the expression of locomotor behavior during the animal's change from an early sessile to a later free-swimming lifestyle and then compare the effects of NO throughout tadpole development. We identify a discrete switch in nitrergic modulation from net inhibition to overall excitation, coincident with the transition to free-swimming locomotion. Additionally, we show in isolated brain stem-spinal cord preparations of older larvae that NO's excitatory effects are manifested as an increase in the probability of spontaneous swim episode occurrence, as found previously for the neurotransmitter dopamine, but that these effects are mediated within the brain stem. Moreover, while the effects of NO and dopamine are similar, the two modulators act in parallel rather than NO operating serially by modulating dopaminergic signaling. Finally, NO's activation of neurons in the brain stem also leads to the release of NO in the spinal cord that subsequently contributes to NO's facilitation of swimming.Publisher PDFPeer reviewe

Using the present to interpret the past: the role of ethnographic studies in Andean archaeology

Within Andean research it is common to use ethnographic analogies to aid the interpretation of archaeological remains, and ethnographers and archaeologists have developed shared research in technology, material culture and material practice. Although most of this research does not follow the detailed recording methods of spatial patterning envisioned in earlier formulations of ethnoarchaeology, it has had a profound effect on how archaeology in the region has been interpreted. This paper uses examples from the study of pottery production to address earlier debates about the use of ethnographic analogy, discusses the dangers of imposing an idealised or uniform vision of traditional Andean societies onto earlier periods (‘Lo Andino’) but stresses the benefits of combining ethnographic and archaeological research to explore continuities and changes in cultural practice and regional variations

Persistent Place-Making in Prehistory: the Creation, Maintenance, and Transformation of an Epipalaeolithic Landscape

Most archaeological projects today integrate, at least to some degree, how past people engaged with their surroundings, including both how they strategized resource use, organized technological production, or scheduled movements within a physical environment, as well as how they constructed cosmologies around or created symbolic connections to places in the landscape. However, there are a multitude of ways in which archaeologists approach the creation, maintenance, and transformation of human-landscape interrelationships. This paper explores some of these approaches for reconstructing the Epipalaeolithic (ca. 23,000–11,500 years BP) landscape of Southwest Asia, using macro- and microscale geoarchaeological approaches to examine how everyday practices leave traces of human-landscape interactions in northern and eastern Jordan. The case studies presented here demonstrate that these Epipalaeolithic groups engaged in complex and far-reaching social landscapes. Examination of the Early and Middle Epipalaeolithic (EP) highlights that the notion of “Neolithization” is somewhat misleading as many of the features we use to define this transition were already well-established patterns of behavior by the Neolithic. Instead, these features and practices were enacted within a hunter-gatherer world and worldview

Pensamiento de una etnógrafa acerca de la interpretación den la arqueología Andina = An ethnographer's thoughts about interpretation in the archaeology of the Andes

En este ensayo se busca ofrecer una perspectiva etnográfica del entendimiento andino de la materialidad en el contexto de la interpretación arqueológica. Se referirá específicamente a algunas de las formas en que la etnografía puede ser de ayuda para el pensamiento arqueológico. En la actualidad, el denominado “giro ontológico” de la antropología desafía a los arqueólogos a comprometerse seriamente con realidades alternativas que cuestionan los términos analíticos de la tradición intelectual “occidental”. // This essay offers an ethnographer’s perspective on Andean understandings of materiality in the context of archaeological interpretation. I confine myself to a few of the ways in which ethnography can inform archaeological thinking. Currently, the so-called “ontological turn” in anthropology challenges archaeologists to engage seriously with alternate realities that defy the analytical terms of “Western” intellectual tradition

The neural basis of escape swimming behaviour in the squat lobster Galathea strigosa. I. Absence of cord giant axons and anatomy of motor neurones involved in swimming

1. The anatomy and physiology of neurones underlying escape swimming behaviour in the squat lobster, Galathea strigosa, have been investigated, and the results are discussed in the context of the evolution of decapod escape behaviour. 2. In contrast to crayfish, hermit crabs and a number of other related decapods, Galathea does not possess a giant fibre system for escape. 3. Fast flexor motor neurones (FFs) and fast extensor motor neurones (FEs) have been shown, by cobalt backfilling, to be homologous with crayfish FFs and FEs in number, size and distribution of somata. A small degree of intersegmental and interspecific variation is noted. The flexor inhibitor (FI) neurone is described in terms of its central anatomy, peripheral function and peripheral branching pattern. In each of these respects the neurone is found to be homologous with the crayfish FI. 5. The neurone homologous with the crayfish motor giant (MoG) in its soma size and position is found to be a typical FF in Galathea. This 'MoGH' contrasts with the crayfish MoG in having central neuropilar arborization and in lacking axonal branches in the connectives. These differences can be accounted for by the absence of cord giant axons.</p

The neural basis of escape swimming behaviour in the squat lobster Galathea strigosa. III. Mechanisms for burst production

1. Intracellular recordings have been made from a variety of phasic motor neurones during expression of the motor programme for backward swimming in Galathea strigosa. 2. Fast flexor motor neurones (FFs) are driven by a large depolarization mediated by chemical synapses and are inhibited in the interburst interval. 3. Fast extensor motor neurones (FEs) are driven by a barrage of unitary EPSPs during the extension phase and may receive unitary synaptic inhibition while the flexors are active. 4. FFs all have similar spike thresholds and fire bursts of spikes superimposed upon the depolarized peak of the input. FEs show a graduation in spike threshold which is correlated with soma size. The largest FEs (type 2) have higher thresholds than smaller FEs (type 1), and fire fewer spikes. 5. The phasic inhibitor motor neurone to flexor muscles (FI) is driven by complex central pathways and fires a single spike shortly following flexion. 6. The extensor inhibitor (EI) appears to receive the same depolarization as do the FFs, but has a low spike threshold and thus fires on the rising phase of the depolarization. Spiking in EI is terminated by unitary IPSPs which occur in phase with FF activity and which may have the same origin as the interburst inhibition seen in the FEs.</p

La ocupación Wari y el culto Inca a Viracocha en Raqchi, Cuzco

El sitio arqueológico de Raqchi es más conocido por su gran edificio Inca, identificado como el “Templo de Viracocha” por fuentes virreinales. El sitio también incluye un sector con 152 estructuras circulares interpretadas como colcas incas por autores que nos preceden. Sin embargo, aunque se ha registrado cerámica incaica al interior de algunas de ellas; la cerámica utilitaria, los restos botánicos carbonizados y los fogones registrados en sus pisos tienen filiación Wari (Horizonte Medio). Por ello, sugerimos que este sector de Raqchi funcionó como un complejo Wari para grupos temporales de trabajo, similares a los evidenciados en los sitios arqueológicos de Pikillacta y Azángaro, lo que a su vez sugiere un aspecto coercitivo en la colonización Wari. Esto lleva a una reevaluación del culto Inca a Viracocha y de la reutilización ritual de los sitios estatales Tiahuanaco y Wari durante el Horizonte Tardío. // The archaeological site of Raqchi is mostly known for its grand Inca edifice., identified in vice royal archives as the ‘Temple of Viracocha’. The site also includes a sector with 152 circular structures interpreted as Inca colcas (storehouses) by earlier authors. Nevertheless, even though Inca pottery has been found in some of these, the utilitarian pottery, the carbonized botanic remains, and the firepits found in their floors have a Wari affiliation (Middle Horizon). It is for this reason that we suggest that this sector of Raqchi functioned as a Wari facility for contemporary labor groups, similar to those identified at the sites of Pikillacta and Azangaro; which suggests a coercive aspect in the Wari colonization of this area. This indicates that a reevaluation of the Inca cult of Viracocha is necessary, in a similar way as is evident in the ritual re-use of the sites of Tiahuanaco and Wari during the Late Horizon