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Ontogenesis of the manual motor systems in a comparative approach in two primates

Abstract

Among primates, grasping constitutes a vital function and many hypotheses suggest the importance of predation and locomotion on fine branches in grasping origins (Sustaita et al., 2013). However, the interactions between behavior, morphology and brain functions are extremely complicated to discover and the evolutionary deduction is almost impossible. In addition, the effects of age on grasping are poorly known whereas an ontogenetic approach could allow understanding, in real time the interactions between these parameters.
The objective of this work is to determine, during the development, the evolution of the behavioral, functional, anatomical and neuronal parameters underlying grasping in a primate: the mouse lemur (Microcebus murinus). This species has already been studied within the framework of the origins of grasping and ageing. Ontogenetic preliminary data allow us to propose a precise protocol to analyze the interactions between capacities to use hands (e.g. grasp the mother, the diverse tree-dwelling substrates, foods), the performances (e.g strengths of grips), the muscular anatomy and the morphometry of the upper limb as well as the associated cerebral electric activity (e.g. EEG to measure the electric activity of neurons in freely-moving animals) and laterality. The individuals will be studied from their birth to the adulthood in a longitudinal way (from J1 to 3 months). Our general hypothesis is that the behavioral and performance parameters will vary according to the developmental stage, in connection with the morpho-functional, anatomical and neurological modifications. This approach will for the first time allow highlighting

  1. the stages of acquisition of grasping,
  2. the part of the morpho-functional and/or neurological parameters in this acquisition
  3. the relation between tree-dwelling locomotion, predation and cortical specialization. This study offers a unique opportunity to understand the complex interactions between all parameters involved to finally discuss the link between ecology, form and function and put in a new light the evolution of grasping.

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