Merle T. Fairhurst

Physiological and Behavioral Responses Reveal 9-Month-Old Infants’ Sensitivity to Pleasant Touch

Caregiving touch has been shown to be essential for the growth and development of human infants. However, the physiological and behavioral mechanisms that underpin infants’ sensitivity to pleasant touch are still poorly understood. In human adults, a subclass of unmyelinated peripheral nerve fibers has been shown to respond preferentially to medium-velocity soft brushing. It has been theorized that this privileged pathway for pleasant touch is used for close affiliative interactions with conspecific individuals, especially between caregivers and infants. To test whether human infants are sensitive to pleasant touch, we examined arousal (heart rate) and attentional engagement (gaze shifts and duration of looks) to varying velocities of brushing (slow, medium, and fast) in 9-month-old infants. Our results provide physiological and behavioral evidence that sensitivity to pleasant touch emerges early in development and therefore plays an important role in regulating human social interactions.

Being and Feeling in Sync with an Adaptive Virtual Partner: Brain Mechanisms Underlying Dynamic Cooperativity

Cooperation is intrinsic to the human ability to work together toward common goals, and depends on sensing and reacting to dynamically changing relationships between coacting partners. Using functional magnetic resonance imaging (fMRI) and a paradigm in which an adaptive pacing signal simulates a virtual partner, we examined the neural substrates underlying dynamic joint action. A single parameter controlled the degree to which the virtual partner adapted its behavior in relation to participant taps, thus simulating varying degrees of cooperativity. Analyses of fMRI data using objective and subjective measures of synchronization quality found the relative balance of activity in two distinct neural networks to depend on the degree of the virtual partners adaptivity. At lower degrees of adaptivity, when the virtual partner was easier to synchronize with, cortical midline structures were activated in conjunction with premotor areas, suggesting a link between the action and socio-affective components of cooperation. By contrast, right lateral prefrontal areas associated with central executive control processes were recruited during more cognitively challenging interactions while synchronizing with an overly adaptive virtual partner. Together, the reduced adaptive sensorimotor synchronization paradigm and pattern of results illuminate neural mechanisms that may underlie the socio-emotional consequences of different degrees of entrainment success.

Sensorimotor synchronization with tempo-changing auditory sequences: Modeling temporal adaptation and anticipation

The current study investigated the human ability to synchronize movements with event sequences containing continuous tempo changes. This capacity is evident, for example, in ensemble musicians who maintain precise interpersonal coordination while modulating the performance tempo for expressive purposes. Here we tested an ADaptation and Anticipation Model (ADAM) that was developed to account for such behavior by combining error correction processes (adaptation) with a predictive temporal extrapolation process (anticipation). While previous computational models of synchronization incorporate error correction, they do not account for prediction during tempo-changing behavior. The fit between behavioral data and computer simulations based on four versions of ADAM was assessed. These versions included a model with adaptation only, one in which adaptation and anticipation act in combination (error correction is applied on the basis of predicted tempo changes), and two models in which adaptation and anticipation were linked in a joint module that corrects for predicted discrepancies between the outcomes of adaptive and anticipatory processes. The behavioral experiment required participants to tap their finger in time with three auditory pacing sequences containing tempo changes that differed in the rate of change and the number of turning points. Behavioral results indicated that sensorimotor synchronization accuracy and precision, while generally high, decreased with increases in the rate of tempo change and number of turning points. Simulations and model-based parameter estimates showed that adaptation mechanisms alone could not fully explain the observed precision of sensorimotor synchronization. Including anticipation in the model increased the precision of simulated sensorimotor synchronization and improved the fit of model to behavioral data, especially when adaptation and anticipation mechanisms were linked via a joint module based on the notion of joint internal models. Overall results suggest that adaptation and anticipation mechanisms both play an important role during sensorimotor synchronization with tempo-changing sequences. This article is part of a Special Issue entitled SI: Prediction and Attention.

Fostering Social Cognition through an Imitation- and Synchronization-Based Dance/Movement Intervention in Adults with Autism Spectrum Disorder: A Controlled Proof-of-Concept Study.

Background: Since social cognition is impaired in individuals with autism spectrum disorder (ASD), this study aimed at establishing the efficacy of a newly developed imitation- and synchronization-based dance/movement intervention (SI-DMI) in fostering emotion inference and empathic feelings (emotional reaction to feelings of others) in adults with high-functioning ASD. Methods: Fifty-five adults with ASD (IQ ≥85) who were blinded to the aim of the study were assigned to receive either 10 weeks of a dance/movement intervention focusing on interpersonal movement imitation and synchronization (SI-DMI, n = 27) or a control movement intervention (CMI, n = 24) focusing on individual motor coordination (2 participants from each group declined before baseline testing). The primary outcome measure was the objective Multifaceted Empathy Test targeting emotion inference and empathic feelings. Secondary outcomes were scores on the self-rated Interpersonal Reactivity Index. The well-established automatic imitation task and synchronization finger-tapping task were used to quantify effects on imitation and synchronization functions, complemented by the more naturalistic Assessment of Spontaneous Interaction in Movement. Results: Intention-to-treat analyses revealed that from baseline to 3 months, patients treated with SI-DMI showed a significantly larger improvement in emotion inference (d = 0.58), but not empathic feelings, than those treated with CMI (d = -0.04). On the close generalization level, SI-DMI increased synchronization skills and imitation tendencies, as well as whole-body imitation/synchronization and movement reciprocity/dialogue, compared to CMI. Conclusions: SI-DMI can be successful in promoting emotion inference in adults with ASD and warrants further investigation.

Segregation and integration of auditory streams when listening to multi-part music

In our daily lives, auditory stream segregation allows us to differentiate concurrent sound sources and to make sense of the scene we are experiencing. However, a combination of segregation and the concurrent integration of auditory streams is necessary in order to analyze the relationship between streams and thus perceive a coherent auditory scene. The present functional magnetic resonance imaging study investigates the relative role and neural underpinnings of these listening strategies in multi-part musical stimuli. We compare a real human performance of a piano duet and a synthetic stimulus of the same duet in a prioritized integrative attention paradigm that required the simultaneous segregation and integration of auditory streams. In so doing, we manipulate the degree to which the attended part of the duet led either structurally (attend melody vs. attend accompaniment) or temporally (asynchronies vs. no asynchronies between parts), and thus the relative contributions of integration and segregation used to make an assessment of the leader-follower relationship. We show that perceptually the relationship between parts is biased towards the conventional structural hierarchy in western music in which the melody generally dominates (leads) the accompaniment. Moreover, the assessment varies as a function of both cognitive load, as shown through difficulty ratings and the interaction of the temporal and the structural relationship factors. Neurally, we see that the temporal relationship between parts, as one important cue for stream segregation, revealed distinct neural activity in the planum temporale. By contrast, integration used when listening to both the temporally separated performance stimulus and the temporally fused synthetic stimulus resulted in activation of the intraparietal sulcus. These results support the hypothesis that the planum temporale and IPS are key structures underlying the mechanisms of segregation and integration of auditory streams, respectively.

The importance of integration and top-down salience when listening to complex multi-part musical stimuli

In listening to multi-part music, auditory streams can be attended to either selectively or globally. More specifically, musicians rely on prioritized integrative attention which incorporates both stream segregation and integration to assess the relationship between concurrent parts. In this fMRI study, we used a piano duet to investigate which factors of a leader-follower relationship between parts grab the listeners attention and influence the perception of multi-part music. The factors considered included the structural relationship between melody and accompaniment as well as the temporal relationship (asynchronies) between parts. The structural relationship was manipulated by cueing subjects to the part of the duet that had to be prioritized. The temporal relationship was investigated by synthetically shifting the onset times of melody and accompaniment to either a consistent melody or accompaniment lead. The relative importance of these relationship factors for segregation and integration as attentional mechanisms was of interest. Participants were required to listen to the cued part and then globally assess if the prioritized stream was leading or following compared to the second stream. Results show that the melody is judged as more leading when it is globally temporally ahead whereas the accompaniment is not judged as leading when it is ahead. This bias may be a result of the interaction of salience of both leader-follower relationship factors. Interestingly, the corresponding interaction effect in the fMRI-data yields an inverse bias for melody in a fronto-parietal attention network. Corresponding parameter estimates within the dlPFC and right IPS show higher neural activity for attending to melody when listening to a performance without a temporal leader, pointing to an interaction of salience of both factors in listening to music. Both frontal and parietal activation implicate segregation and integration mechanisms and a top-down influence of salience on attention and the perception of leader-follower relations in music.