In this study, the relationship between physiological arousal, as indexed by heart rate variability, was examined in boys with fragile X syndrome and typically developing boys matched on chronological age. In addition, the relationship of heart activity to clinical and molecular factors in the group of boys with FXS was examined. Results suggest that boys with fragile X syndrome have higher levels of heart activity during the passive phases, as reflected in shorter heart periods. This high level of heart activity appears to be due to increased sympathetic activity and reduced parasympathetic activity. Boys with FXS did not display the expected patterns of heart activity in response to phases of increasing challenge and sympathetic and parasympathetic systems did not appear coordinated in these boys with FXS. Clinical factors may be related to neural regulation of heart activity while molecular factors do not appear to be.

Results

Boccia, M. L., & Roberts, J. E. (2000). Behavior and autonomic nervous system function assessed via heart period measures: The case of hyperarousal in boys with fragile X syndrome. Behavior Research Methods, Instruments, and Computers, 32, 5-10.

Roberts, J. E., Boccia, M. L., Bailey, D. B., Hatton, D. D., & Skinner, M. (2001). Cardiovascular indicators of arousal in boys affected by fragile X syndrome. Developmental Psychobiology, 39(2), 107-123.