Yoke Motor Learning in the Fetal Rat: A Model System for Prenatal Behavioral Development

Abstract

A great deal has been learned about fetal sensory experience and associative learning over the past four decades, but far less is known about how experience may contribute to the prenatal development of the motor system. Indeed, the earliest rudiments of behavior consist of seemingly random spontaneous movements, and experimental demonstrations that spontaneous activity can be generated by isolated elements of the spinal cord have promoted the misconception that experience plays little or no role in early motor development. Building upon an animal model that permits direct assessment of behavior in the rat fetus, my laboratory has developed a motor learning paradigm to study how kinesthetic feedback from motor performance can lead to adaptive changes in motor coordination. Fetal limb movement is manipulated with an interlimb yoke, which creates a physical linkage between two limbs. The yoke results in a gradual increase in conjugate limb movements during a 30-min training session. After yoke training, rat fetuses continue to show enhanced coordination of the trained limbs, which is evident in both the timing and spatial organization of limb movements. Moreover, savings in the rate of acquisition also is evident when fetuses experience yoke training in a second session. These findings argue that fetuses are not automatons but rather are responsive to kinesthetic feedback and can alter the frequency, patterning, and coordination of movement in response to sensory challenges and biomechanical perturbations of the motor system.