Involuntary Left-Right Antagonism: A Supposed Archaic Sign of Neural Immaturity?

Abstract

The aim of this study is to show that toddlers are not yet able to perform synchronous bilateral symmetrical hand and arm movements, and a minority even tends to perform involuntarily bimanual left-right antagonistic movements that are regarded as archaic 'trunk movements,' which will disappear with age. Ninety-seven typical children, 49 toddlers (TD's) (3 yrs 0 months-3 yrs 12 months) and 48 preschoolers (PS's) (4 yrs 0 months-4 yrs 12 months), 48 boys and 49 girls, were asked to imitate two types of bilateral movements after a demonstration, namely proximal rotational movements of the arms in the sagittal plane and distal supination-pronation movements at low speed, followed by acceleration on request. The differences were calculated using logistic regression analysis. All the children were able to perform the movements, but TD's displayed less proximal arm synchronicity than PS's. Proximal antagonistic movements were more common in TD's than PS's, decreasing with age, and differences occurred more often after acceleration. The differences were also indicative of a decrease in age in the case of distal bimanual movements, but fewer differences were found to be significant. TD's have not yet fully reached the stage where bimanual movements are symmetrical and synchronous, but they attain the symmetrical stage in the limbs proximally before dis-tally. A minority of the children, mainly TD's, revert to involuntary bimanual antagonism, thus confirming the hypothesis of Mesker, who referred to them as 'trunk movements. It draws the attention to a relatively unknown infantile reflex pattern, antagonistic movements, the retention of which is a sign of immaturity. This could contribute to developmental coordination disorder (DCD).