Development of adaptive sensorimotor control in infant sitting posture
Introduction
Postural control is an important motor skill acquired during early development. To control the multi-segmented body in various conditions, a reliable and adaptive relationship between action and perception is necessary. Evidence of adaptive sensorimotor control in posture has been shown in adults [1], [2] and in children [3], [4], [5]. Little is known about how this type of control develops during infancy.
Young adults entrain their standing posture to the frequency properties of vision and somatosensory information [1], [6], [7]. The frequency response of this sensory-postural relationship demonstrates an inverted-U pattern with the greatest in-phase entrainment near 0.2 Hz and weaker and out-of-phase entrainment as the stimulus frequency decreases or increases [6], [7]. Furthermore, adults’ postural sway is proportional to the stimulus amplitude within a range. When the amplitude exceeds a certain value, postural response decreases [2], [8]. This change in the postural response to a change in the sensory stimuli indicates sensory re-weighting, a critical component of the adaptive sensorimotor control [1], [2], [9]. When a source of sensory information is unreliable, the postural system needs to attenuate this source of information and increase reliance on another modality. This sensory re-weighting process has been shown in children as young as 4 years of age [3] but has not been investigated in very young children or infants.
Newborn infants show directionally appropriate and velocity-scaled head response to visual flow information [10], suggesting that the visual–postural relationship may be a fundamental component of the sensorimotor system. A few studies have investigated infants’ postural responses to changes in the frequency of visual stimuli [11], [12], [13]. However, the results were conflicting. While some studies showed that infants’ postural entrainment increased as the frequency of the visual motion increased [11], [12], one study reported a linear decline in sway coherence as a function of stimulus frequency [13]. Furthermore, the developmental changes in infants’ visual–postural coupling were inconsistent between the studies [11], [12]. These conflicting results may be due to differences in the postural measures as well as the range of sensory properties employed in the studies. Since children were shown to respond to a wider frequency range of visual stimuli compared to adults [5], a sufficient range of sensory properties is required to better characterize the sensorimotor relationships in infants’ postural control.
In the present study, we sought to systematically examine the dynamic visual–postural relationship in infants as they develop postural control. Specifically, we examined infants’ ability to adapt their sitting posture to different properties of the visual signal, i.e., frequency and amplitude. Incorporating a wide range of input frequency and amplitude, we addressed the following research questions: (1) does the adult patter (inverted-U) of visual–postural coupling exist in early infancy? (2) is sensory re-weighting a fundamental process of postural control present in young infants? Using a cross-sectional design, we also examined how the adaptive visual–postural relationship may differ by infants’ advances and experience in postural development from sitting to standing and finally to walking.
Section snippets
Participants
Twenty healthy infants (13 boys) composed four groups (each n = 5): (1) sitting onset (SO; aged 6.7 ± 1.1 months; 6.0 ± 5.1 days after sitting onset), (2) standing alone (ST; aged 10.6 ± 1.2 months; 28.8 ± 11.9 days before walking onset), (3) walking onset (WO; aged 11.7 ± 1.4 months; 8.8 ± 8.1 days after walking onset), and (4) 1-year post-walking (W12; aged 23.5 ± 1.2 months; 11.7 ± 1.0 months after walking onset). Sitting onset was when the infant could sit without support for 10 s. Standing alone was when the
Results
All infants completed the experiment except that one sitting onset infant was unable to remain sitting in the A12 condition. MST results showed a significant group effect (p < 0.05). One-year post-walking infants engaged in the sitting task longer than all other infants (MST 36.5 ± 8.9 and 25.8 ± 15.6 s, respectively). No significant difference was found among amplitude conditions or the three younger groups. Infants’ postural responses at head, upper and middle trunk showed similar patterns among the
Infants show adult-like patter of visual–postural coupling
Our study is the first to show an inverted-U pattern for the frequency response of infants’ postural control to visual stimuli. From a few months post-sitting to one year post-walking, infants demonstrated higher gain responses at 0.52 and 0.76 Hz than at 0.12 and 1.24 Hz. Consistent with previous studies [11], [12], we found higher gain response to 0.5–0.6 Hz than to 0.2–0.3 Hz in sitting infants. Furthermore, with a wider frequency range, we were able to reveal an adult-like inverted-U pattern of
Conclusion
Our results show that, from a few months post-sitting to 1-year post-walking, infants are able to adapt their postural behavior to an oscillating visual stimulus and demonstrate sensory re-weighting ability. While the experienced sitters and walkers showed adult-like frequency- and amplitude-dependent features of their visual–postural relationship, newly sitting infants demonstrated highly variable postural sway and did not respond to the visual stimulus. We suggest that visual–postural
Acknowledgements
We much appreciated the infants and their parents for their time and effort they gave for participating in this study. We also thank Dr. Tim Kiemel for his advice in data analyses and the undergraduate students who assisted in data collection and reduction.
Conflict of interest statement
The authors declare that there are no known conflicts of interest regarding the work described in the present manuscript.
References (28)
- et al.
Multisensory fusion: simultaneous re-weighting of vision and touch for the control of human posture
Brain Res Cogn Brain Res
(2002) - et al.
Optic flow sensitivity in neonates
Infant Behav Dev
(2000) - et al.
Visual information and body sway coupling in infants during sitting acquisition
Infant Behav Dev
(2000) - et al.
Analysis of the perception–action cycle for visually induced postural sway in 9-month-old sitting infants
Infant Behav Dev
(2000) - et al.
Two steps forward and one back: learning to walk affects infants’ sitting posture
Infant Behav Dev
(2007) Sensorimotor integration in human postural control
J Neurophysiol
(2002)- et al.
Development of multisensory reweighting for posture control in children
Exp Brain Res
(2007) - et al.
Postural control in children. Coupling to dynamic somatosensory information
Exp Brain Res
(2003) Children's postural sway in response to low- and high-frequency visual information for oscillation
J Exp Psychol Hum Percept Perform
(1997)- et al.
Frequency dependency of the action–perception cycle for postural control in a moving visual environment: relative phase dynamics
Biol Cybern
(1994)
Multisensory information for human postural control: integrating touch and vision
Exp Brain Res
Role of somatosensory and vestibular cues in attenuating visually induced human postural sway
Exp Brain Res
Postural orientation and equilibrium
Perception-action coupling in the development of visual control of posture
J Exp Psychol Hum Percept Perform
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