Mu Desynchronization to Observation of Gesture Mediates the Relation Between Gesture Experience and Language Development

• In Event: 2-128 - Function and Development of the Mirror System in Infancy and Toddlerhood

Integrative Statement

Action understanding is proposed to be a foundation for communicative development. It is thought that infants apply a similar process of interpreting the goal-structure of actions as they do to the understanding of others’ gestures and spoken language. The mirror neuron system (MNS), as indexed by activation of the motor system during both performance and observation of actions, has been implicated as a neural correlate for action understanding and may be recruited for understanding both gestures and speech. However, this has not yet been examined in infants, when gesture and language are just emerging. Further, one’s experience with actions influences action understanding, however it is unknown whether experience with gestures will impact MNS activity. This study examined whether experience with gestures is related to recruitment of the MNS during observation of gestures in infancy, and whether individual differences in this activity support communicative development. This study focused specifically on pointing gestures, one of the most common gestures used in infancy.
Infant-parent dyads visited the lab twice. At the first visit, when infants were 10- to 12-months old, parent and infant pointing production, infant receptive vocabulary, and infant MNS activity were measured. Infant pointing was measured dichotomously at baseline via parent report (i.e., parents indicated if their child had or had not yet started pointing). Receptive vocabulary was measured via parent report (number of words understood). Parent pointing was measured as the number of points produced during a 10-minute free play. Infant MNS activity was measured using the EEG mu rhythm while infants observed an experimenter pointing, wherein more negative scores indicate stronger MNS activity. Infants’ experience with points was manipulated through a parent-directed intervention aimed at increasing parents’ pointing with their child. Parents were randomly assigned to either receive the pointing intervention, or to a passive control group. At follow-up, one month after baseline, parent pointing, infant vocabulary, and infant MNS activity were reassessed.
81 parent-infant dyads participated (39 female infants, 74 mothers). At baseline, infants showed significant MNS activity when observing the experimenter point (Figure 1). Parents in the training group exhibited a significant increase in pointing from baseline to follow-up, t(34)=6.58, p<.001. Infants in the training group exhibited increased MNS activity from baseline to follow-up, whereas infants in the control group did not (Figure 2A). A latent change score model was fitted to the data to examine continuous relations between parent pointing, infant MNS activity, and infant receptive vocabulary. Increases in parents’ pointing predicted increases in infants’ MNS activity, B=-0.15, p<.01, which in turn predicted increases in infants’ receptive vocabulary, B=-2.55, p<.01 (Figure 2B). The specific indirect effect from parent pointing to infant vocabulary through infant MNS activity was also significant, B=.37, p=.03. These data suggest that the MNS plays a role in infants’ communicative development, and that experience with gestures can impact the mirroring response when observing others’ gesture. These findings contribute to our understanding of the mechanisms that support social communicative growth in the first few years of life.

Authors

• Virginia Salo, University of Maryland, College Park
  Presenting Author

• Ranjan Debnath, University of Maryland, College Park
  Non-Presenting Author

• Meredith Rowe, Harvard University
  Non-Presenting Author