George F. Michel - US grants

Two experiments are proposed which describe intermanual coordination and intermanual transfer of haptic experience during the period of infancy when the corpus callosum first begins to show electrophysiological evidence of function. Each of the proposed procedures have proven to be effective indicators of callosal functioning in animal studies and in studies of callosectomized patients but neither has been employed previously for investigating infant sensorimotor ability. Experiment 1 provides a description of the spatial and temporal pattern of organization involved in intermanual coordination of the movements of the two hands during the bimanual reaching of 7-15 month old infants. Examination of the effects of perturbing the actions of one hand (by unexpected and expected changes in load and trajectory) on the pattern of coordination, means that a procedure commonly used in study of the organization of motor control in adults will be applied to the study of infant motor control. Using equivalent procedures will help forge links between theory of motor control in infants and adults. Intermanual coordination is an important aspect of most theories of infant development. However, research has typically focused on describing the occurrence of this pattern rather than on the specific aspects of how it is organized. Experiment 2 uses a simple learning procedure (employing a novel but spontaneous behavioral response) to examine the ability of infants to discriminate the properties of objects by haptic perception. The experiment will identify the effects of stimulus properties (form, texture, temperature) and hand (right or left) used to perceive the stimuli on the infant's ability to learn a haptic discrimination and to transfer this learning to the use of the other (untrained) hand. This procedure opens the possibility of systematic examination of the information processing aspects of haptic perception and allows for direct psychological examination of the processes of interhemispheric communication. Both experiments approach the investigation of infant sensorimotor ability from a neuropsychological perspective. In each, the subject variables of sex, age, and handedness status are used as prediction variables because they have been known to contribute to important individual differences in neuropsychological investigations of hemispheric specialization of function and interhemispheric interaction.

biomedical equipment purchase;

Why are some people left-handed? Are there two (right- and non-right-handed), three (right-, left-, and mixed-handed) categories or is handedness a quantitative trait with relatively arbitrarily defined categories? With right-handedness dominating in the population, left-handedness and mixed handedness become atypical. Why, then, is atypical handedness associated with atypical hemispheric specialization for language and other psychological functions? Why is atypical handedness a marker for the development of various forms of socio-emotional and cognitive disorders? The proposed project provides crucial information about the early development of handedness that will help form the foundation for the finding answers to these questions. During the age of 6 to 14 months infants develop proficiency for apprehending objects, manipulating them, and employing complex bimanual manipulations (with action differences between the hands) that facilitate tool use, construction of artifacts, and solution to physical problems. Hand-use preferences for these skills appear during this period and play an important role in the distinction of what makes the actions skillful. The proposed project will chart the development of hand-use preferences for each of three manual skills (prehension, unimanual manipulation, and role differentiated bimanual manipulation), the relations among these skills, and their relation to the infant's age, neuromotor development, genotype and development of tool-use and object construction skills. Using a large sample and sophisticated quantitative techniques, different patterns in the development (as measured by age and/or neuromotor maturity) of lateralization of manual skill may be identified that can be compared to the infant's genotype, and tool-use and construction abilities.