Infants with complex congenital heart disease (CCHD) require palliative surgery of their heart in the first weeks of life. Long-term developmental outcomes in infants with CCHD is increasingly becoming an area of concern for medical and rehabilitation professionals as these infants are now surviving into adulthood. Recent work has focused on identifying impairments in cognition, motor, and autonomic nervous system function during preschool and school age in those with CCHD and brain injury in infancy. It is unknown if impaired cognitive, motor, and autonomic nervous system function are identifiable during early infancy in infants with CCHD. Since infants with CCHD demonstrate similarly immature brain as preterm infants, who are well known as a high-risk population for developmental impairments, a group of preterm infants and a group of typically developing (TD) infants were also included for the same tests. The first purpose of this research was to examine cognitive, motor, and autonomic function in infants with CCHD, infants with TD, and infants born preterm at 3 months of corrected age (CA). The second purpose of this research was to identify the associations between the cognitive performance, specifically learning or not learning, and the function autonomic, motor, and state organizational systems in infants with CCDH, infants with TD, and infants born preterm. The synactive theory is a model used to describe how the organization of different body systems influences neurobehaviors in preterm infants; it was used as the conceptual framework in this research.Learning and short-term memory were evaluated with the mobile paradigm. In the mobile paradigm task, infants’ kicking movement causes the mobile to move, which produces visual and auditory feedback. This process allows infants to learn a cause-and-effect relationship. The mobile paradigm was used to test learning on Day 1, and short-term memory on Day 2. Learning and short-term memory were measured within each infant group. The three groups of infants demonstrated learning in the mobile paradigm task; only infants with TD demonstrated short-term memory, which indicated impaired short-term memory in infants with CCHD, and in preterm infants.General development (cognitive, motor, and language domains) was evaluated with the Bayley Scales of Infant development 3rd version (Bayley-III). The composite scores of Bayley-III in each domain were compared between infants with TD and infants with CCHD, and between infants with TD and preterm infants. We found that infants with CCHD did not show significantly lower composite scores of Bayley-III compared to infants with TD. Preterm infants showed significantly lower composite scores in cognitive domain of Bayley-III than infants with TD.Autonomic Nervous System (ANS) Function was evaluated with high-frequency heart rate variability (HF HRV) measured with electrocardiography (ECG) before, during, and after the mobile paradigm. The HF HRV measured the level of parasympathetic activity. Decreases in HF HRV indicate a withdrawal of parasympathetic activity and result in more dominant sympathetic control, which occurs when infants are showing a stress-response. Infants with TD did not show significant changes in HF HRV throughout the mobile paradigm task, and this indicated the mobile paradigm maybe not challenging enough to cause measureable autonomic regulation in infants with TD. Infants with CCHD showed a trend of decrease in HF HRV in the mobile paradigm and significant recovery in HF HRV after the task; this result indicated that infants with CCHD may show withdrawal of parasympathetic activity as a stress-response in the mobile paradigm task, but recovered after the task. Preterm infants demonstrate a stress-response by showing significant decrease in HF HRV in the mobile paradigm, and failed to recover after the task.To evaluate the association between learning performance and the function of autonomic, motor, and state organization systems, the general development measured with Bayley-III, autonomic regulation measured with HF HRV, and state organization measured with the number of arousal state transitions after the mobile paradigm task were compared between learners and non-learners regardless of infant groups. The correlations between intra-/inter-limb kicking patterns in spontaneous kicking and normalized kicking rate (absolute kicking rate normalized to the baseline kicking rate) in the mobile paradigm were assessed to examine the association between motor function and learning performance in the mobile paradigm. Learners in the TD and CCHD combined group, and in the TD and preterm combined group showed more responsive HF HRV changes in the mobile paradigm task compared to non-learners. Infants who showed more matured intra-limb kicking patterns in spontaneous kicking were likely to show more increase in kicking rate in the mobile paradigm task.The findings from our studies showed that infants with CCHD have impaired short-term memory and autonomic function compared to infants with TD; the developmental outcomes between infants with CCHD and preterm infants were not as similar, as expected. In addition, the functions of different body systems may contribute infants’ behaviors including the performance in a cognitive task. These findings taken together suggested that impairments are identifiable in early infancy and intervention to enhance autonomic function and to target different developmental domains should be considered in infants with CCHD.