اتونوم فعالیت سیستم عصبی کودکان سن پیش دبستانی که لکنت زبان دارند

Purpose The purpose of this study was to investigate potential differences in autonomic nervous system (ANS) activity to emotional stimuli between preschool-age children who do (CWS) and do not stutter (CWNS). Methods Participants were 20 preschool-age CWS (15 male) and 21 preschool-age CWNS (11 male). Participants were exposed to two emotion-inducing video clips (negative and positive) with neutral clips used to establish pre-and post-arousal baselines, and followed by age-appropriate speaking tasks. Respiratory sinus arrhythmia (RSA)—often used as an index of parasympathetic activity—and skin conductance level (SCL)—often used as an index of sympathetic activity—were measured while participants listened to/watched the audio–video clip presentation and performed a speaking task. Results CWS, compared to CWNS, displayed lower amplitude RSA at baseline and higher SCL during a speaking task following the positive, compared to the negative, condition. During speaking, only CWS had a significant positive relation between RSA and SCL. Conclusion Present findings suggest that preschool-age CWS, when compared to their normally fluent peers, have a physiological state that is characterized by a greater vulnerability to emotional reactivity (i.e., lower RSA indexing less parasympathetic tone) and a greater mobilization of resources in support of emotional reactivity (i.e., higher SCL indexing more sympathetic activity) during positive conditions. Thus, while reducing stuttering to a pure physiological process is unwarranted, the present findings suggest that the autonomic nervous system is involved. Educational Objectives: The reader will be able to: (a) summarize current empirical evidence on the role of emotion in childhood stuttering; (b) describe physiological indexes of sympathetic and parasympathetic activity; (c) summarize how preschool-age children who stutter differ from preschool-age children who do not stutter in autonomic activity; (d) discuss possible implications of current findings in relation to the development of childhood stuttering.

The association between emotional processes and developmental stuttering has attracted increasing interest over the past decade (e.g., Anderson et al., 2003, Arnold et al., 2011, Choi et al., 2013, Eggers et al., 2009, Eggers et al., 2010, Eggers et al., 2012, Felsenfeld et al., 2010, Johnson et al., 2010, Karrass et al., 2006, Ntourou et al., 2013, Schwenk et al., 2007 and Walden et al., 2012). Recent reviews of the literature have concluded that there may be a relation between the two (for review, see Jones et al., 2014 and Kefalianos et al., 2012). Despite inconsistencies in the literature, there are also consistencies. For example, reviews noted that preschool-age children, who stutter (CWS) compared to children who do not stutter (CWNS), exhibit (1) less adaptability, (2) poorer attention span/persistency and attention regulation, and (3) more negative mood. Although these findings do not indicate whether emotions are causes or the consequences of stuttering, they provide replicated support for an association between emotional state regulation and childhood stuttering. 1.1. Emotion and stuttering 1.1.1. Emotions and childhood stuttering Studies using caregiver report questionnaires documented that CWS, compared to CWNS, displayed: (a) less temperamental adaptability, distractibility, and rhythmicity ( Anderson et al., 2003), (b) increased reactivity and greater difficulty regulating emotions ( Karrass et al., 2006), (c) poorer attention regulation skills ( Felsenfeld et al., 2010 and Karrass et al., 2006), skill implicated in emotion regulation ( Rothbart, Ahadi, & Evans, 2000), and (d) less inhibitory control and attention shifting, as well as greater anger/frustration ( Eggers et al., 2010). In contrast, Lewis and Golberg (1997) found that CWS were less negative in their emotions and more adaptable than CWNS. Despite some incongruence, taken as a whole these findings provide building evidence that CWS versus CWNS display consistent differences in a variety of emotion-related processes. Using direct observation of behavior or experimental testing, researchers report that preschool-age CWS, compared to CWNS, exhibited: (a) difficulty habituating to irrelevant background stimuli ( Schwenk et al., 2007), (b) more negative emotional expressions in a disappointing gift procedure ( Johnson et al., 2010) and during neutral and frustrating conditions ( Ntourou et al., 2013), (c) less efficiency of the orienting subsystem of the attentional system ( Eggers et al., 2012; cf. Johnson, Conture, & Walden, 2012), and (d) poorer inhibitory control during a Go/NoGo task ( Eggers, De Nil, & Van den Bergh, 2013). Within-group behavioral observations have indicated that increases in CWS's stuttering are related to: (a) decreased duration and frequency of behavioral regulatory strategies (Arnold et al., 2011), (b) increased emotional reactivity concurrent with decreased regulation (Walden et al., 2012), (c) negative emotion prior to and during utterances (Jones, Conture, & Walden, 2014), particularly following positive conditions (Johnson et al., 2010 and Jones et al., 2014). In contrast, CWS's stuttering frequency was lower during narratives that followed diverting attention away from preceding non-speech tasks (Ntourou et al., 2013). Further, more behaviorally inhibited CWS (i.e., children exhibiting strong reactions to novelty or change), when compared to less behaviorally inhibited CWS, exhibited more stuttering during a conversation with an unfamiliar experimenter (Choi et al., 2013). These behavioral observations provide insights into CWS’ emotional responding to specific challenging situations, as well as concomitant changes in speech fluency. The above findings have resulted in a partial picture of the association between emotion and childhood stuttering. Including psychophysiological methods to assess the two branches (i.e., parasympathetic and sympathetic) of the autonomic nervous system (ANS) may increase our understanding of this association in preschool-age CWS. Measures of autonomic activity would provide an important feature of emotional reactivity and regulation and possibly identify covert indicators that may precede, follow, or act concurrently with more overt expressions of emotion. Since much of the empirical evidence regarding emotion and childhood stuttering comes from parent-report and behavioral observations, a psychophysiological perspective is largely lacking (cf. Arnold et al., 2011). This dearth in knowledge, in part, motivated the present study. 1.1.2. Autonomic nervous system activity of adults who stutter Despite the lack of knowledge about ANS activity of preschool-age CWS, psychophysiological concomitants of stuttering in adults have been empirically studied for several decades (e.g., Alm and Risberg, 2007, Fletcher, 1914, Gray and Karmen, 1967 and Reed and Lingwall, 1980). Methods have varied considerably as technology and theories have advanced, which may, in part, contribute to a lack of consistent evidence that psychophysiological factors are associated with stuttering. For example, although adults who stutter often report anxiety about stuttering (e.g., Craig, 1990 and Craig et al., 2003), this is not always associated with increases in autonomic arousal (e.g., Dietrich & Roaman, 2001). This is particularly evident in recent investigations, which have reported heart rate increases either prior to or during speech for both adults who stutter (AWS) and adults who do not stutter (AWNS), but that such increases are often less marked for AWS ( Caruso et al., 1994, Peters and Hulstijn, 1984 and Weber and Smith, 1990). Alm (2004) argued that these findings may represent “anticipatory anxiety resulting in a ‘freezing response”’ that may be related to parasympathetic inhibition of heart rate. Alm further argued that heart rate is not thought to be a reliable index of sympathetic or parasympathetic activity, but rather represents the cumulative influences of both sympathetic and parasympathetic activity. Therefore, in order to attain a more “pure” index of the activity of the two branches of the ANS, measures that isolate specific branches need to be used. These measures should be conceptualized using a well-established framework to understand separate and concurrent influences on psychological and behavioral processes. 1.2. Psychophysiological measures of emotion Before introducing the indices of ANS activity used in the present study, we briefly discuss the role of physiology in emotion. At present there is no consensus in the literature on a definition of emotion. However, Cabanac (2002) proposed that it be operationalized as “any mental experience with high intensity and high hedonic content (pleasure/displeasure).” Cabanac further predicted that objective physiological signs of emotion should accompany such mental experiences. Cabanac's view corresponds with Sonnemans and Frijda's (1994) view that physiological changes are an important component to the intensity of emotion. Izard (2010) compiled responses to various questions on emotion from 35 “distinguished” emotion researchers, and while the consensus was that there is no unitary concept, physiological activity was commonly included as a defining feature of emotion. Therefore, while we acknowledge that the physiological activity used to assess emotion in the present study does not solely represent emotion, we assert that it is an important component of emotion that furthers our understanding of emotion and childhood stuttering. The importance of physiological activity to a comprehensive account of emotion is underscored (see below) by the Polyvagal Theory ( Porges, 2007 and Porges, 2011), a model providing a conceptual framework for the present study. 1.2.1. Polyvagal Theory The Polyvagal Theory proposes a hierarchical model comprised of three neural circuits that regulate autonomic activity and support distinct behavioral processes (for detailed overview of the Polyvagal Theory, see Porges, 1995, Porges, 2007 and Porges, 2011). In brief, the Polyvagal Theory describes three phylogenetically ordered neural circuits that regulate autonomic state in vertebrates. In humans these circuits are linked behaviorally to (1) social communication (e.g., facial expression, vocalization, listening), (2) mobilization (e.g., fight–flight behaviors), and (3) immobilization (e.g., feigning death and behavioral shutdown) (see Table 1). The Polyvagal Theory proposes an integrated “social communication system” that involves regulation of the striated muscles of the face and head (i.e., via cranial nerves V, VII, IX, X, XI) and regulation of visceral organs above the diaphragm via a myelinated vagal pathway. This vagal circuit fosters calm states by facilitating parasympathetic nervous system influence on the heart and inhibits sympathetic activation. The “mobilization system”—related to sympathetic nervous system activation—promotes “fight-flight” behaviors. Within the Polyvagal Theory, the mobilization system is also characterized by a synchronous withdrawal of the parasympathetic influence on the heart to facilitate an efficient sympathetic activation. Lastly, the earliest, phylogenetically most primitive system is the “immobilization system” which depends on the unmyelinated vagus with its primary regulation of subdiaphragmatic organs (e.g., gut). This system promotes behavioral shutdown in response to life threat and is associated with massive slowing of heart rate (i.e., clinical bradycardia) that would lead to a rapid drop in blood pressure and fainting (i.e., vasovagal syncope).

The present findings provide a physiological “perspective” to interpret earlier empirical investigations of emotion reactivity and childhood stuttering based on caregiver-report questionnaires (e.g., Anderson et al., 2003, Eggers et al., 2010, Felsenfeld et al., 2010 and Karrass et al., 2006) and behavioral observations ( Arnold et al., 2011, Eggers et al., 2012, Johnson et al., 2010, Schwenk et al., 2007 and Walden et al., 2012). Consistent with previous studies, the present physiological findings indicate that emotional processes differ between preschool-age CWS and their CWNS peers. Based on the present findings CWS, when compared to fluent peers, have greater stress vulnerability (lower parasympathetic tone during baseline), as well as greater mobilization of resources in support of emotional reactivity (more sympathetic activity during positive conditions). This pattern of response may divert CWS's resources away from concurrent attentional, cognitive and speech-language processes needed to fluently initiate and/or maintain communication. The empirical search for answers to either possibility is important to a comprehensive understanding of childhood stuttering. It is likely that the reported group differences in emotional processes represent a complex interleaving of genetic (Rothbart, 2007 and Saudino, 2005) and experiential/environmental (Goldsmith et al., 1987) influences. While these findings may reflect a “rebounding effect” due to these children's, although relatively limited, experience with or reaction to stuttering (Treon, 2010), differences in emotional processes for preschool-age CWS are not likely to be solely caused by experience with stuttering. Thus, while reducing stuttering to a pure physiological process is unwarranted, the present findings suggest that the autonomic nervous system is involved.