Perception of Motion Transparency in 5-Month-Old Infants

Developmental changes in visual-cognitive and attentional functions in infancy

BACKGROUND

Identifying developmental changes in visual-cognitive and attentional functions during infancy may lead to early diagnosis of neurodevelopmental disorders such as ASD and ADHD.

AIMS

To clarify the developmental changes in visual-cognitive and attentional functions during infancy (3-36 months of age).

STUDY DESIGN

Cross-sectional study.

SUBJECTS

We included 23, 24, 31, and 26 participants aged 3, 9, 18, and 36 months, respectively (full-term births). Fifteen children who cried intensely or whose data could not be accurately recorded were excluded.

OUTCOME MEASURES

Three activities were given to each child while they were seated in front of a gaze-tracking device to evaluate re-gaze, motion transparency, and color-motion integration. We analyzed whether the child's attention shifted to the new stimulus in their peripheral vision in the re-gaze task. In the motion transparency and color-motion integration tasks, two images were presented simultaneously on the screen. In the motion transparency task, participants preferred random dots moving in opposite directions; in the color-motion task, they preferred subjective contours from apparent motion stimuli consisting of random red and green dots with different luminance.

RESULTS

In the re-gaze task, fewer 3-month-olds gazed at the new target than other age groups participants. All ages showed preference for target stimuli in the motion transparency task, but 3-month-olds showed significantly lower preference in the color-motion integration task.

CONCLUSION

These tasks may be useful for measuring visual-cognitive and attentional functions in infants.

Infants see illusory motion in static figures

We investigated illusory motion perception in 6-to-8-month-old infants using a static figure which produces strong illusory motion. In experiment 1 we prepared a control figure, which was physically similar to the illusory motion figure but which did not produce illusory motion. We presented the illusory figure and the control figure side-by-side, and measured infants' looking time at the target illusory figure. Results showed that the infants' looking time at the illusory figure was significantly longer than that for the control. In experiment 2 we made another set of stimuli consisting of the same local pattern used in experiment 1, but which did not produce illusory motion. The results showed that no preferences were observed in experiment 2. These results suggest that 6-to-8-month-old infants perceive illusory motion in static figures.

fMRI–Adaptation Studies of Viewpoint Tuning in the Extrastriate and Fusiform Body Areas

People are easily able to perceive the human body across different viewpoints, but the neural mechanisms underpinning this ability are currently unclear. In three experiments, we used functional MRI (fMRI) adaptation to study the view-invariance of representations in two cortical regions that have previously been shown to be sensitive to visual depictions of the human body—the extrastriate and fusiform body areas (EBA and FBA). The BOLD response to sequentially presented pairs of bodies was treated as an index of view invariance. Specifically, we compared trials in which the bodies in each image held identical poses (seen from different views) to trials containing different poses. EBA and FBA adapted to identical views of the same pose, and both showed a progressive rebound from adaptation as a function of the angular difference between views, up to ∼30°. However, these adaptation effects were eliminated when the body stimuli were followed by a pattern mask. Delaying the mask onset increased the response (but not the adaptation effect) in EBA, leaving FBA unaffected. We interpret these masking effects as evidence that view-dependent fMRI adaptation is driven by later waves of neuronal responses in the regions of interest. Finally, in a whole brain analysis, we identified an anterior region of the left inferior temporal sulcus (l-aITS) that responded linearly to stimulus rotation, but showed no selectivity for bodies. Our results show that body-selective cortical areas exhibit a similar degree of view-invariance as other object selective areas—such as the lateral occipitotemporal area (LO) and posterior fusiform gyrus (pFs).

Sensitivity to rotational motion in early infancy

Sensitivity to rotational motion, one of the fundamental components of optic flow, was tested in infants aged 2 and 3 months. The infants in both groups showed significant sensitivity to rotational motion only in the high-speed condition (10.62 degrees/s). There was no significant increase in motion sensitivity between 2 and 3 months of age, indicating that there is not a significant developmental change during this period. A comparison of our results with previous findings that showed a significant increase in radial motion sensitivity between 2 and 3 months suggests that different motion sensitivities have different developmental time courses.