skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Mechanistic Hypotheses for Proprioceptive Sensing Within the Avian Lumbosacral Spinal Cord
Synopsis Animals need to accurately sense changes in their body position to perform complex movements. It is increasingly clear that the vertebrate central nervous system contains a variety of cells capable of detecting body motion, in addition to the comparatively well-understood mechanosensory cells of the vestibular system and the peripheral proprioceptors. One such intriguing system is the lower spinal cord and column in birds, also known as the avian lumbosacral organ (LSO), which is thought to act as a set of balance sensors that allow birds to detect body movements separately from head movements detected by the vestibular system. Here, we take what is known about proprioceptive, mechanosensory spinal neurons in other vertebrates to explore hypotheses for how the LSO might sense mechanical information related to movement. Although the LSO is found only in birds, recent immunohistochemical studies of the avian LSO have hinted at similarities between cells in the LSO and the known spinal proprioceptors in other vertebrates. In addition to describing possible connections between avian spinal anatomy and recent findings on spinal proprioception as well as sensory and sensorimotor spinal networks, we also present some new data that suggest a role for sensory afferent peptides in LSO function. Thus, this perspective articulates a set of testable ideas on mechanisms of LSO function grounded in the emerging spinal proprioception scientific literature.  more » « less
Award ID(s):
2233350
PAR ID:
10445407
Author(s) / Creator(s):
; ; ; ;
Publisher / Repository:
Oxford University Press
Date Published:
Journal Name:
Integrative And Comparative Biology
Volume:
63
Issue:
2
ISSN:
1540-7063
Format(s):
Medium: X Size: p. 474-483
Size(s):
p. 474-483
Sponsoring Org:
National Science Foundation
More Like this
  1. ; (, Journal of Experimental Biology)
    ABSTRACT The integration of sensory information is required to maintain body posture and to generate robust yet flexible locomotion through unpredictable environments. To anticipate required adaptations in limb posture and enable compensation of sudden perturbations, an animal's nervous system assembles external (exteroception) and internal (proprioception) cues. Coherent neuronal representations of the proprioceptive context of the body and the appendages arise from the concerted action of multiple sense organs monitoring body kinetics and kinematics. This multimodal proprioceptive information, together with exteroceptive signals and brain-derived descending motor commands, converges onto premotor networks – i.e. the local neuronal circuitry controlling motor output and movements – within the ventral nerve cord (VNC), the insect equivalent of the vertebrate spinal cord. This Review summarizes existing knowledge and recent advances in understanding how local premotor networks in the VNC use convergent information to generate contextually appropriate activity, focusing on the example of posture control. We compare the role and advantages of distributed sensory processing over dedicated neuronal pathways, and the challenges of multimodal integration in distributed networks. We discuss how the gain of distributed networks may be tuned to enable the behavioral repertoire of these systems, and argue that insect premotor networks might compensate for their limited neuronal population size by, in comparison to vertebrate networks, relying more heavily on the specificity of their connections. At a time in which connectomics and physiological recording techniques enable anatomical and functional circuit dissection at an unprecedented resolution, insect motor systems offer unique opportunities to identify the mechanisms underlying multimodal integration for flexible motor control. 
    more » « less
  2. ; ; ; ; ; ; (, eLife)
    Although specialized mechanosensory cells are found across animal phylogeny, early evolutionary histories of mechanoreceptor development remain enigmatic. Cnidaria (e.g. sea anemones and jellyfishes) is the sister group to well-studied Bilateria (e.g. flies and vertebrates), and has two mechanosensory cell types - a lineage-specific sensory-effector known as the cnidocyte, and a classical mechanosensory neuron referred to as the hair cell. While developmental genetics of cnidocytes is increasingly understood, genes essential for cnidarian hair cell development are unknown. Here we show that the class IV POU homeodomain transcription factor (POU-IV) - an indispensable regulator of mechanosensory cell differentiation in Bilateria and cnidocyte differentiation in Cnidaria - controls hair cell development in the sea anemone cnidarian Nematostella vectensis. N. vectensis POU-IV is postmitotically expressed in tentacular hair cells, and is necessary for development of the apical mechanosensory apparatus, but not of neurites, in hair cells. Moreover, it binds to deeply conserved DNA recognition elements, and turns on a unique set of effector genes - including the transmembrane-receptor-encoding gene polycystin 1 - specifically in hair cells. Our results suggest that POU-IV directs differentiation of cnidarian hair cells and cnidocytes via distinct gene regulatory mechanisms, and support an evolutionarily ancient role for POU-IV in defining the mature state of mechanosensory neurons. 
    more » « less
  3. ; ; (, Proceedings of the Royal Society B: Biological Sciences)
    null (Ed.)
    Body mass affects many biological traits, but its impacts on immune defences are fairly unknown. Recent research on mammals found that neutrophil concentrations disproportionately increased (scaled hypermetrically) with body mass, a result not predicted by any existing theory. Although the scaling relationship for mammals might predict how leucocyte concentrations scale with body mass in other vertebrates, vertebrate classes are distinct in many ways that might affect their current and historic interactions with parasites and hence the evolution of their immune systems. Subsequently, here, we asked which existing scaling hypothesis best-predicts relationships between body mass and lymphocyte, eosinophil and heterophil concentrations—the avian functional equivalent of neutrophils—among more than 100 species of birds. We then examined the predictive power of body mass relative to life-history variation, as extensive literature indicates that the timing of key life events has influenced immune system variation among species. Finally, we ask whether avian scaling patterns differ from the patterns we observed in mammals. We found that an intercept-only model best explained lymphocyte and eosinophil concentrations among birds, indicating that the concentrations of these cell types were both independent of body mass. For heterophils, however, body mass explained 31% of the variation in concentrations among species, much more than life-history variation (4%). As with mammalian neutrophils, avian heterophils scaled hypermetrically ( b = 0.19 ± 0.05), but more steeply than mammals (approx. 1.5 ×; 0.11 ± 0.03). As such, we discuss why birds might require more broadly protective cells compared to mammals of the same body size. Overall, body mass appears to have strong influences on the architecture of immune systems. 
    more » « less
  4. ; ; ; ; ; ; ; (, Science Advances)
    Mechanosensory corpuscles detect transient touch and vibration in the skin of vertebrates, enabling precise sensation of the physical environment. The corpuscle contains a mechanoreceptor afferent surrounded by lamellar cells (LCs), but corpuscular ultrastructure and the role of LCs in touch detection are unknown. We report the three-dimensional architecture of the avian Meissner (Grandry) corpuscle acquired using enhanced focused ion beam scanning electron microscopy and machine learning-based segmentation. The corpuscle comprises a stack of LCs interdigitated with terminal endings from two afferents. Simultaneous electrophysiological recordings from both cell types revealed that mechanosensitive LCs use calcium influx to trigger action potentials in the afferent and thus serve as physiological touch sensors in the skin. The elaborate architecture and bicellular sensory mechanism in the corpuscles, which comprises the afferents and LCs, create the capacity for nuanced encoding of the submodalities of touch. 
    more » « less
  5. ; ; ; (, Proceedings of the National Academy of Sciences)
    Spinal injuries in many vertebrates can result in partial or complete loss of locomotor ability. While mammals often experience permanent loss, some nonmammals, such as lampreys, can regain swimming function, though the exact mechanism is not well understood. One hypothesis is that amplified proprioceptive (body-sensing) feedback can allow an injured lamprey to regain functional swimming even if the descending signal is lost. This study employs a multiscale, integrative, computational model of an anguilliform swimmer fully coupled to a viscous, incompressible fluid and examines the effects of amplified feedback on swimming behavior. This represents a model that analyzes spinal injury recovery by combining a closed-loop neuromechanical model with sensory feedback coupled to a full Navier–Stokes model. Our results show that in some cases, feedback amplification below a spinal lesion is sufficient to partially or entirely restore effective swimming behavior. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email