The consummatory origins of visually guided reaching in human infants: a dynamic integration of whole-body and upper-limb movements.
Reaching-to-eat (skilled reaching) is a natural behaviour that involves reaching for, grasping and withdrawing a target to be placed into the mouth for eating. It is an action performed daily by adults and is among the first complex behaviours to develop in infants. During development, visually guided reaching becomes increasingly refined to the point that grasping of small objects with precision grips of the digits occurs at about one year of age. Integration of the hand, upper-limbs, and whole body are required for successful reaching, but the ontogeny of this integration has not been described. The present longitudinal study used Laban Movement Analysis, a behavioural descriptive method, to investigate the developmental progression of the use and integration of axial, proximal, and distal movements performed during visually guided reaching. Four infants (from 7 to 40 weeks age) were presented with graspable objects (toys or food items). The first prereaching stage was associated with activation of mouth, limb, and hand movements to a visually presented target. Next, reaching attempts consisted of first, the advancement of the head with an opening mouth and then with the head, trunk and opening mouth. Eventually, the axial movements gave way to the refined action of one upper-limb supported by axial adjustments. These findings are discussed in relation to the biological objective of reaching, the evolutionary origins of reaching, and the decomposition of reaching after neurological injury.
Department of Neuroscience, Canadian Centre for Behavioural Neuroscience, The University of Lethbridge, Lethbridge, Alberta, Canada. afra@psych.ubc.ca
Afra
A
Foroud
Ian Q
IQ
Whishaw
D001132:Arm / Q000502:physiology; D001696:Biomechanical Phenomena; D002657:Child Development / Q000502:physiology*; D003259:Consummatory Behavior / Q000502:physiology*; D003627:Data Interpretation, Statistical; D005247:Feeding Behavior; D005260:Female; D006225:Hand / Q000502:physiology; D018737:Hand Strength / Q000502:physiology; D019416:Head Movements / Q000502:physiology; D006801:Humans; D007206:Individuality; D007223:Infant; D008137:Longitudinal Studies; D008297:Male; D009055:Mouth / Q000502:physiology; D009068:Movement / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology*; D012727:Sex Characteristics; D034941:Upper Extremity / Q000254:growth & development / Q000502:physiology*; D014741:Video Recording