There are many scientific and clinical questions that require consideration of physiological responses concomitantly with behavioral responses. While in some cases, global assessments of physiological systems whose measurement provides a window into the system is sufficient, others require precise time-series analysis of moment by moment integration of behavior and physiology. The case of hyperarousal as a source of behavior problems in children with Fragile X Syndrome is one such example. Hyperarousal refers to the idea that these individuals have difficulty regulating arousal levels due to dysfunctional autonomic nervous systems (ANS). It has been suggested that the stereotypies and behavior problems often seen in these children may be behavioral attempts to modulate their physiological arousal. To test this hypothesis, it is necessary to record physiological markers of ANS arousal in real time, and in such a way as to permit integration with ongoing, real-time recorded behavior. In this presentation, we report the methods we have employed to test this hypothesis.

Heart activity, from which information can be derived about ANS function, is monitored with the Minilogger 2000 system (Mini-Mitter Co.), which employs Polar belts to transmit R-wave information to their logger. The Polar system is proprietary software that has very high accuracy in detection of R-wave peaks in a heart signal. The logger computes inter-beat intervals or summary heart rates, along with other information, and stores the data for download to a computer at a later time. Software permits extraction of ASCII files that can be imported into other software systems. Behavior is video-recorded for later coding, and an event-code marker is inserted into the logger file on tape to synchronize behavior and heart activity data. Behavior is coded with The Observer (Noldus Information Technology), which then integrates the heart activity data with the ODF file to provide information about mean heart period during each behavior scored as well as during each experimental phase. Because The Observer can integrate any time-series physiological data with behavior in ODF files, it is possible to use multiple heart activity measures to examine the sympathetic and parasympathetic nervous system responses to experimental manipulations and behaviors.

Applying these techniques to a sample of boys with Fragile X Syndrome (FraX) and a group of typically developing boys, we examined both raw heart activity data and spectral analysis measures of parasympathetic and sympathetic nervous systems’ contributions to the heart activity in relation to experimental challenges. We found that boys with FraX had lower parasympathetic activity, rather than higher sympathetic system activity. We also found that they were differentially responsive to experimental challenge. These results have important implications both for our understanding of the basic nervous system dysfunction in FraX and for the strategies likely to be effective in terms of pharmacological intervention with these children. These methods can be used in a variety of contexts to examine any physiological measures that can be collected as a time series.