Specificity of practice effects on elementary neuromotor patterns.

Abstract

The specificity of the effects of practice on 2 elementary neuromotor patterns, stepping and sitting, was investigated. Thirty-two 6-week-old male infants were assigned to 1 of 5 groups: Three experimental groups received 2,3-min daily sessions of exercise of stepping, sitting, or both (3 min each), whereas 2 control groups received no exercise. After 7 weeks, infants who received elicitation of the stepping pattern, alone or in combination with exercises, stepped more than infants who received no exercise or exercises only. Infants who received exercises alone or in addition to stepping exercises sat upright longer than infants who received no exercise or stepping exercises only. These experimental data for 2 neuromotor patterns indicate that the short-term effects of practice are specific to the patterns trained. Training influences early motor development: Practice facilitates stepping in 8-week-old infants, prevents its disappearance over the first few months of life, and leads to an earlier onset of unaided walking (Zelazo, Zelazo, & Kolb, 1972a, 1972b). In addition to elucidating the nature of these influences, further research on the effects of practice on early motor functions may increase one's understanding of the functions themselves and may constrain speculation regarding the relation of these functions to later developmental milestones. Although frequently referred to as reflexes in order to capture the fact that they seem to be involuntary (Touwen, 1984), some early functions such as stepping and sitting in the air (Katona, 1989) are probably best characterized as neuromotor patterns that tend to repeat themselves when activated. This view is consistent with observations and research reported by Katona (1988,1989) and Thelen (e.g., Thelen & Fisher, 1982). Moreover, discussion of stepping and analogous rhythmic functions in terms of patterns and underlying pattern generators is supported by research on the neural bases of complex, rhythmic behavior in nonhuman vertebrates (Delcomyn, 1980; Getting, 1988). At present, speculation regarding the nature of these patterns and the way in which practice affects them is largely unconstrained. One possibility is that the neuromotor patterns serve as elements in more complex motor routines, such as unaided