The development of upper limb movements: from fetal to post-natal life.

BACKGROUND: The aim of this longitudinal study was to investigate how the kinematic organization of upper limb movements changes from fetal to post-natal life. By means of off-line kinematical techniques we compared the kinematics of hand-to-mouth and hand-to-eye movements, in the same individuals, during prenatal life and early postnatal life, as well as the kinematics of hand-to-mouth and reaching-toward-object movements in the later age periods. METHODOLOGY/PRINCIPAL FINDINGS: Movements recorded at the 14(th), 18(th) and 22(nd) week of gestation were compared with similar movements recorded in an ecological context at 1, 2, 3, 4, 8, and 12 months after birth. The results indicate a similar kinematic organization depending on movement type (i.e., eye, mouth) for the infants at one month and for the fetuses at 22 weeks of gestation. At two and three months such differential motor planning depending on target is lost and no statistical differences emerge. Hand to eye movements were no longer observed after the fourth month of life, therefore we compared kinematics for hand to mouth with hand to object movements. Results of these analyses revealed differences in the performance of hand to mouth and reaching to object movements in the length of the deceleration phase of the movement, depending on target. CONCLUSION/SIGNIFICANCE: Data are discussed in terms of how the passage from intrauterine to extra-uterine environments modifies motor planning. These results provide novel evidence of how different types of upper extremity movements, those directed towards one's own face and those directed to external objects, develop

Movement Time for reaching to the mouth and to the object respectively at 4, 8 and 12 months of age.

<p>Movement Time for reaching to the mouth and to the object respectively at 4, 8 and 12 months of age.</p

The two types of movements considered during the pre-natal period and the first 3 months of post-natal life: hand to mouth (A and C) and hand to eye (B and D) performed by a fetus at 18 weeks of gestation and by a 3 month old infant.

<p>The two types of movements considered during the pre-natal period and the first 3 months of post-natal life: hand to mouth (A and C) and hand to eye (B and D) performed by a fetus at 18 weeks of gestation and by a 3 month old infant.</p

Movement Time, expressed in milliseconds, in the pre and post-natal periods.

<p>Movement Time, expressed in milliseconds, in the pre and post-natal periods.</p

Frequency of occurrence for the three different types of movements analysed at three different times during the prenatal life and six different times during the first year of life for each foetus/infant.

<p><i>Notes:</i> wk = weeks; mo = months.</p

Characteristics of the mothers involved in the study.

<p>Notes. SES social economical status, BMI body mass index, BP blood pressure, AF amniotic fluid.</p

Types of movements.

<p>a, Video frame representing a self-directed movement towards the mouth. b, Video frame representing a self-directed movement towards the eye. c, Video frame representing the foetus reaching towards and “caressing” the back of the sibling. d, Video frame representing the foetus reaching towards and “caressing” the head of the sibling.</p

Kinematics adaptation to the properties of the target.

<p>Movement duration and deceleration time for self-directed movements towards the mouth and the eye region, and movements directed towards the sibling at the 14^th and 18^th week of gestation. a, Movement duration for movements performed towards the co-twin was longer than for self-directed movements towards the eye or the mouth. Duration of movements towards the eye region was longer than for those directed towards the mouth. b, The percentage of time spent decelerating was greater for movements towards the co-twin than for movements towards the eye or the mouth. Deceleration time for movements towards the eye region was longer than that for those directed towards the mouth. For both dependent measures the size of the target effect was comparable at the 14^th and 18^th week. Error bars represent the standard error of the means.</p

Movement duration for different types of movement at the 14^th and 18^th week of gestation for each foetus.

<p>Movement duration for different types of movement at the 14^th and 18^th week of gestation for each foetus.</p