Summary: The neural basis for a preference of yawning is apparent in babies as young as 5 months.
Source: Chuo University
Contagious yawning is observed in many mammals, but there is no such report in human babies. Whether babies recognize yawning is an unanswered question.
A new study in Chuo University and Japan Women’s University provides a new insight into this question. It suggested that 5- to 8-month-old babies show face-specific brain activity in response to yawning. This study was published online in Scientific Reports on July 23, 2019.
In this study, at first, researchers focused on the babies’ looking time to yawning and mouth movement: opening mouth and moving tongue sideways against the cheek. In the experiment, 3- to 8- month-old babies were presented yawning and mouth movement side by side, and they looked at the yawning for longer than at the mouth movement. This result suggests that babies in first half-year of their life prefer yawning.
Next, researchers measured the 5- to 8- month-old babies’ brain activity while they viewed yawning and mouth movement each using functional near-infrared spectroscopy (fNIRS). From previous fNIRS studies, it was found that the hemodynamic responses in the occipitotemporal areas increased in response to facial movement because this area plays a role in face processing. Based on such evidence, it was expected that the hemodynamic responses increased when babies were viewing yawning compared to mouth movement. As expected, babies’ hemodynamic response increased in response to yawning, but not to mouth movement. This implies that the neural basis of preference for yawning is seen even in younger babies.
“This is the first study revealing the babies’ preference for yawning, and its neural activity related to yawning processing,” said Shuma Tsurumi from Chuo University.
Funding: This study was supported by a Grant-in-Aid from the Japan Society for the Promotion of Science (JSPS) Fellows (19J21422), a Grant-in-Aid for Scientific Research on Innovative Areas, ”Construction of the Face-Body Studies in Transcultural Conditions” (17H06343), from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT), and a Grant-in-Aid for Scientific Research (B) from the JSPS (26285167).
About this neuroscience research article
Source: Chuo University Media Contacts: Shuma Tsurumi, Masami Yamaguchi – Chuo University Image Source: The image is credited to Chuo University.
Infant brain activity in response to yawning using functional near-infrared spectroscopy
Yawning is contagious in human adults. While infants do not show contagious yawning, it remains unclear whether infants perceive yawning in the same manner as other facial expressions of emotion. We addressed this problem using functional near-infrared spectroscopy (fNIRS) and behavioural experiments. We confirmed behaviourally that infants could discriminate between yawning and unfamiliar mouth movements. Furthermore, we found that the hemodynamic response of infants to a yawning movement was greater than that to mouth movement, similarly to the observations in adult fMRI study. These results suggest that the neural mechanisms underlying yawning movement perception have developed in advance of the development of contagious yawning.