Baby steps: investigating the development of perceptual–motor couplings in infancy

Abstract

There are cells in our motor cortex that fire both when we perform and when we observe similar actions. It has been suggested that these perceptual-motor couplings in the brain develop through associative learning during correlated sensorimotor experience. Although studies with adult participants have provided support for this hypothesis, there is no direct evidence that associative learning also underlies the initial formation of perceptual–motor couplings in the developing brain. With the present study we addressed this question by manipulating infants’ opportunities to associate the visual and motor representation of a novel action, and by investigating how this influenced their sensorimotor cortex activation when they observed this action performed by others. Pre-walking 7–9-month-old infants performed stepping movements on an infant treadmill while they either observed their own real-time leg movements (Contingent group) or the previously recorded leg movements of another infant (Non-contingent control group). Infants in a second control group did not perform any steps and only received visual experience with the stepping actions. Before and after the training period we measured infants’ sensorimotor alpha suppression, as an index of sensorimotor cortex activation, while they watched videos of other infants’ stepping actions. While we did not find greater sensorimotor alpha suppression following training in the Contingent group as a whole, we nevertheless found that the strength of the visuomotor contingency experienced during training predicted the amount of sensorimotor alpha suppression at post-test in this group. We did not find any effects of motor experience alone. These results suggest that the development of perceptual–motor couplings in the infant brain is likely to be supported by associative learning during correlated visuomotor experience.

Predictive action tracking without motor experience in 8-month-old infants

“…This finding is consistent with previous studies that demonstrated more motor system involvement during the observation of visually trained versus untrained stimuli (Burke et al, 2010, Cross et al, 2009, de Klerk et al, 2015, Frey and Gerry, 2006) and supports the idea that observational experience might shape the sensorimotor regions of the brain in a similar manner as physical experience does (Burke et al, 2010, Cross et al, 2009). Additionally, these findings provide further support for the idea that motor expertise is not a prerequisite for motor system activation during action prediction (Abreu et al, 2012, Schubotz, 2007, Southgate and Begus, 2013).…”

“…However, instead we found that infants were able to distinguish between the correctly and incorrectly continued actions without receiving any visual training with the stimuli. These findings suggest that infants in our previous study (de Klerk, Johnson, Heyes et al, 2015) were also able to predict the kinematics of the stepping actions even before being familiarised with the stimuli. However, possibly the visual experience that these infants received over the course of that study may have allowed them to make more exact predictions about the stepping actions at post-test, such that even small deviations from these predictions increased the prediction error and hence the amount of sensorimotor alpha suppression (Cross et al, 2012).…”

“…As our participants were not able to walk yet, this finding demonstrates that motor experience is not necessary for accurate predictive action tracking. Based on the findings of a previous study, in which we found greater sensorimotor cortex activation after repeated exposure to these infant stepping stimuli (de Klerk, Johnson, Heyes et al, 2015), we were initially expecting that infants might need visual training with the stimuli before they would be able to predictively track the actions. However, instead we found that infants were able to distinguish between the correctly and incorrectly continued actions without receiving any visual training with the stimuli.…”

“…The stimulus material for the test trials consisted of video clips of six different infants performing stepping actions on an infant treadmill filmed from a sagittal view (see de Klerk, Johnson, Heyes et al, 2015). All stepping actions were rightward movements but as the infants were on a treadmill, there was little horizontal translation.…”

“…We then measured infants’ looking times to static test postures after correctly versus incorrectly continued actions. We used infant stepping stimuli because a previous study suggested that visual experience with this type of action might trigger predictive processes (de Klerk, Johnson, Heyes, & Southgate, 2015). We used inverted stepping actions as control stimuli to check whether extrapolation from the movement prime would be sufficient to elicit predictive responses.…”