Animal-to-Animal Variability in Neuromodulation and Circuit Function

Abstract

Each animal alive in the world is different from all other individuals, while sharing most attributes of form and function with others of the same species. Still other attributes are shared within a phylum, and still others are common to most eukaryotic organisms. All animals have mechanisms that modulate the strength of their synapses or alter the intrinsic excitability of component neurons. What animal-to-animal variability in behavior arises from differences in neuronal structure, ion channel expression, or connectivity, and what variability arises from neuromodulation of brain states? Conversely, can robust behavior be maintained despite variability in circuit components by the action of neuromodulatory inputs? These are fundamental issues relevant to all nervous systems that have been illuminated by many years of study of the small, rhythmic motor circuits found in the crustacean stomatogastric nervous system.

In vivoEffects of Temperature on the Heart and Pyloric Rhythms in the Crab,Cancer borealis

“…The STG maintains its triphasic rhythm to control the movement of the muscles, 606 and is robust to several global perturbations, including temperature (Soofi et al, 2014; 607 Tang et al, 2010; Tang et al, 2012) and pH (Haley, Hampton and Marder, 2018). 608 Previous work has shown the importance of animal-to-animal variability in responses to 609 such perturbations Hamood and Marder, 2014; Hamood and 610 . Interestingly, there are differential sensitivities of the responses of 611 isolated STGs and cardiac ganglia to pH, again with the cardiac ganglion being more 612 robust.…”

Homeostatic plasticity of excitability in crustacean central pattern generator networks

“…Recently these findings have been incorporated into an elegant computational modeling framework that puts forth a hypothesis by which activity-dependent homeostatic regulation rules can generate correlations in the steady-state distribution of ion channels [47,48](Figure 3). This homeostatic regulation is based on a calcium-dependent model of self-regulating rhythmically bursting cells [50] (Figure 3A), generating distinct outputs via plasticity in conductance expression as a result of cell-type specific channel expression rates [48] (Figure 3B). These tuning rules give rise to correlated conductance levels that differ across neuron output types (Figure 3C), and are consistent with the biological data for STG cells [25,46].…”

The complexity of small circuits: the stomatogastric nervous system

“…Given that circuit components are both variable across individuals and malleable to many neuromodulators, it is surprising that circuit activity is robust and neuromodulators cause consistent activity changes across individuals [16,52,53]. However, at least in the long term, neuromodulation does not seem to be the cause of variability, but can reduce it.…”