Behavior and autonomic nervous system function assessed via heart period measures: The case of hyperarousal in boys with fragile X syndrome

Abstract

Physiological responses may inform us about and help us to interpret behavioral responses. For example, hyperarousal may be a source of behavior problems in children with fragile Xsyndrome (FXS), To evaluate this approach, we examined heart period data in specific contexts in boys with FXSand in normally developing chronological-age-matched boys, Spectral analysis was used to evaluate the parasympathetic and sympathetic nervous systems' contributions to heart period, Boys with FXS had shorter interbeat intervals, lower parasympathetic activity, and similar sympathetic activity, Also, the groups were differentially responsive to experimental challenge, These results have important implications for our understanding of the basic nervous system dysfunction in FXS and for the strategies likely to be effective in terms of pharmacological intervention with these children. These methods can be applied to a variety of contexts and populations, including children who are sensory defensive, socially avoidant, inattentive, or hyperactive.Investigations of individual differences are often enhanced by concomitant consideration of physiological and behavioral responses, and data from multiple sources can often strengthen a behavioral study. Psychobiological perspectives combine these two responses in looking at integrative analyses of both behavior and physiology. Although valuable, collection and coordination of these data often pose significant challenges. Specifically, it is challenging to find a method of data collection that allows integration between two systems, is noninvasive and tolerable to subjects, yet is reliable in terms of signal detection. Although these challenges are present in most studies integrating physiological and behavioral data, they are amplified when working with children who have developmental delays and/or known psychopathologies, particularly when sensory defensiveness is a behavioral characteristic. For example, completing functional magnetic resonance image scanning with unmedicated autistic children would be very challenging, given their difficulties in following directions, remaining still, and tolerating sensory stimulation.Hyperarousal as a source of behavior problems in children with fragile X syndrome (FXS) is a case in which 5 consideration of physiological responses may inform us about and help us to interpret behavioral responses. Although numerous studies have cited evidence of high levels of behavioral arousal in individuals affected by FXS (Cohen, 1995; Merenstein et a1., 1996), there has been only one study ofphysiological arousal and no study that has integrated behavioral and physiological sources of arousa1. Inthis paper, we will use a study of hyperarousal in boys with FXS as a model of integrating multiple systems in order to study physiological arousal and its relation to behavioral problems.

Attentional dysfunction, impulsivity, and resistance to change in a mouse model of fragile X syndrome.

“…A study of heart rate variability in boys with FXS compared to age-matched normal controls further supports hyperarousal in FXS (Boccia and Roberts, 2000). In this study, boys with FXS had a faster heart rate and lower parasympathetic activity compared to controls indicating autonomic dysfunction and another mechanism of hyperarousal in individuals with FXS.…”

“…Furthermore, the pattern of responses to stimulation of individuals with fragile X in one sensory modality predicted responses in the other sensory systems, suggesting a general abnormality in sensory processing. Moreover, the magnitude of EDR responses in individuals with fragile X were highly correlated 11 with their FMR-protein expression level such that higher levels of FMRP are associated with more normal response patterns .A study of heart rate variability in boys with FXS compared to age-matched normal controls further supports hyperarousal in FXS (Boccia and Roberts, 2000). In this study, boys with FXS had a faster heart rate and lower parasympathetic activity …”

Validating the Construct of Coercion in Family Routines: Expanding the Unit of Analysis in Behavioral Assessment with Families of Children with Developmental Disabilities

“…Their facial expressions and movements grew agitated and their speech or vocalizations became louder and/or distressed. When children with disabilities enter a heightened state of arousal, it may take longer for them to return to a previously calm state, even when the surrounding conditions no longer present triggers for escape-motivated problem behavior (Boccia & Roberts, 2000;Freeman, Horner, & Reichle, 1999). Although parents may have reduced or withdrawn a demand, the children's high state of arousal may not have decreased quickly enough to allow the child to reciprocate by reducing or terminating problem behavior.…”

Postadolescent Changes in Regional Cerebral Protein Synthesis: AnIn VivoStudy in theFmr1Null Mouse

“…The hypothalamus supplies a major input to the dorsal motor nucleus of the vagus, and, via the parasympathetic system, the dorsal motor nucleus of the vagus regulates visceral functions. Parasympathetic dysregulation, hyperarousal, and hyperactivity are all characteristic of FrX patients (Boccia and Roberts, 2000;Hagerman, 2002). Fmr1 null mice are hyperactive (Qin et al, 2002), are susceptible to audiogenic seizures, and have an increase in prepulse inhibition and auditory startle responses (Chen and Toth, 2001).…”