Independent digit movements and precision grip patterns in 1–5-month-old human infants: hand-babbling, including vacuous then self-directed hand and digit movements, precedes targeted reaching
Introduction
The development of adult skilled movements of the hand and digits depends upon the maturation of the nervous system and learning, but the precise contributions of each process is not fully understood. This is due in part to gaps in descriptions of the development of skilled movements and in part to an incomplete understanding of the maturation and function of different parts of the motor system. One gap that is especially noteworthy in the description of hand and digit movements in infants relates to the behaviors that occur between the time of birth and about 5 months of age. Non-random changes in hand and digit movements are reported in the human fetus (Sparling, Van Tol, & Chescheir, 1999), and the earliest observed grasping behaviors, including the automatic grasping reflex, the flexion of the digits elicited by a contact stimulus to the palm, have been described in infants shortly after birth (Twitchell, 1970). Beyond this, descriptions of visually guided reaches (DiFranco et al., 1978, Konczak et al., 1995; Von Hofsten, 1979; White, Castle, & Held, 1964), purposeful grasping (Halverson, 1937; Hirschel, Pehoski, & Coryell, 1990; Touwen, 1995, Twitchell, 1965a), and fine prehension (Butterworth, Verweij, & Hopkins, 1997; Castner, 1932, Hohlstein, 1982; Wimmers, Savelsbergh, Beek, & Hopkins, 1998) have been described in infants older than 6 months of age. Although several attempts have been made to categorize the progression of the development of hand and digit movements from reflexive to purposeful movements, none has included the unsolicited behaviors that occur in the first five postnatal months.
The absence of descriptions of hand and digit movements in the first 5 months of life in humans may relate to the hypotheses concerning the maturation and function of the pyramidal tract and its direct connections to the motor neurons of the spinal cord, which are proposed to underlie skilled movements of the hands and digits (Bernhard, Bohm, & Peterson, 1953; Porter & Lemon, 1993; Tower, 1940). Based on anatomical studies in monkeys (Felix and Wiesendanger, 1971, Flament et al., 1992, Galea and Darian-Smith, 1995, Lawrence and Hopkins, 1976, Olivier et al., 1997), it has been proposed that these direct connections are established relatively late in infancy, circa 7–12 months, at about the time when visually guided movements of the hand develop (Butterworth et al., 1997, Halverson, 1931, Halverson, 1937). Thus, in the absence of these connections, it might be expected that there would be no hand and digit movements of interest prior to the emergence of visually guided reaching. Nevertheless, more recent electrophysiological and anatomical studies suggest that in humans, direct connections of the pyramidal tract to motor neurons are established before birth (Eyre, Miller, Clowry, Conway, & Watts, 2000). These more recent findings suggest that a reexamination of the hand and digit movements made by infants between birth and the development of visually guided reaches might be worthwhile.
This was the purpose of the present study. Rather than developing test situations for examining hand and digit movements, an ethological approach of filming and classifying spontaneous hand and digit movements in waking infants ranging from 1 to 5 months of age was used.
Section snippets
Subjects
Six normal, full-term infants (two boys and four girls) participated in the study. None of the infants had sensory or motor impairments. The initial experimental session began when the infants were approximately 2 weeks old, and the sessions ended when they were approximately 22 weeks old. This period braced the time between which spontaneous movements were virtually absent and visually guided reaching commenced.
Video records
The subjects were videotaped using either a Sony HI8 video camera or a Sony digital
Results
In the earlier weeks, the infants mainly made fists with the thumb either tucked beneath or wrapped around the digits. Much of these earlier movements included reflexive behaviors, such as the tonic neck reflex and the moro reflex. The infants then began to make a variety of digit and hand movements that became increasingly complex. Pre-precision and precision grip patterns were observed at this time. At first, these movements were quite frequently associated with body and arm movements but
Discussion
The results of the present study show that the spontaneous hand and digit movements of infants ages 1–5 months are numerous and complex. A classification and description of the many and varied hand and digit movements and their relationship to other movements of the body and limbs was beyond the scope of the current study. Nevertheless, we identified four exemplar grasping movements, which are closely related to developmental age. These movements consisted of the formation of fists,
Acknowledgements
Research was supported by the Natural Sciences and Engineering Research Council of Canada and the Canadian Stroke Network. The authors thank Bogdan Gorny and Paul Whishaw for help in editing the photos. Thank you to Susan Byers, Charlene Anderson, Tosha Calder, Dic and Vicki Charge, Quintin Steynen, Renae Calder, and Carmen Hanson for filming their babies, and the authors also thank Logan Oddie for suggesting this project to us when he was 3 months old.
References (34)
The neurological development of prehension: A developmental neurologist’s view
International Journal of Psychophysiology
(1995)The automatic grasping responses of infants
Neuropsychologia
(1965)- et al.
Language, gesture, and the developing brain
Developmental Psychobiology
(2002) - et al.
Investigations on the organization of the corticospinal system in monkeys (Macaca mulatta)
Acta Physiological Scandinavica
(1953) - et al.
The development of prehension in infants: Halverson revisited
British Journal of Developmental Psychology
(1997) The development of fine prehension in infancy
Genetic Psychology Monographs
(1932)- Caulfield, R. A. (2001). Infants and toddlers (p. 200). New Jersey: Prentice...
- et al.
Reaching in very young infants
Perception
(1978) - et al.
Functional corticospinal projections are established prenatally in the human foetus permitting involvement in the development of spinal motor centres
Brain
(2000) - et al.
Pyramidal and non-pyramidal motor cortical effects on distal forelimb muscles of monkeys
Experimental Brain Research
(1971)
The development of corticomotoneuronal projections investigated using magnetic brain stimulation in the infant macaque
Journal of Physiology (London)
Postnatal maturation of the direct corticospinal projections in the macaque monkey
Cerebral Cortex
Altered precision grasping in stumptail macaques after fasciculus cuneatus lesions
Somatosensory and Motor Research
An experimental study of prehension in infants by means of systematic cinema records
Genetic Psychology Monographs
Studies of the grasping responses of early infancy
Journal of Genetic Psychology
Environmental support and the development of grasp in infants
American Journal of Occupational Therapy
The development of prehension in normal infants
American Journal of Occupational Therapy
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