Sex differences in small-magnitude heart-rate responses to sexual and infant-related stimuli: a psychophysiological approach

Putting salient vocalizations in context: Adults' physiological arousal to emotive cues in domestic and external environments

Salient vocalizations are automatically processed and distinguished from emotionally irrelevant information. However, little is known of how contextual, gender and attentional variables interact to modulate physiological responses to salient emotive vocalizations. In this study, electrocardiogram (ECG) was utilized to investigate differences in peripheral nervous activity of men and women to infant cry (IC), infant laughter (IL) and adult cry (AC) in two different situational contexts: the domestic environment (DE) and the outside environment (OE). As the mental state of listeners can affect their response to vocalizations, a between-subject design was applied: one group was instructed to imagine being inside the scenes (Task 1: explicit task), and the other group was told to look at the scenes (Task 2: implicit task). Results revealed that females exhibited lower inter-beat interval (IBI) index in the OE condition, as compared to both males in OE and females in DE conditions, suggesting greater physiological arousal amongst females in response to vocalizations in an outside environment. Additionally, Task 1 revealed that males demonstrated higher Low Frequency/High Frequency (LFHF) index towards AC than IL. Task 2 showed the same association between these two sounds in females. The implicit task also elicited lower LFHF index in response to both IL and IC than control sound (CS), only amongst females. Findings highlight the important roles that contextual information and cognitive demand play in regulating physiological responses to salient emotive vocalizations. Integrated perspectives of physiological responses to emotive vocalizations that consider the influence of internal (adult mental states) and external (environment) contextual information will provide a better understanding of mechanisms underlying emotional processing of salient social cues.

Sensing emotion in voices: Negativity bias and gender differences in a validation study of the Oxford Vocal ('OxVoc') sounds database

Emotional expressions are an essential element of human interactions. Recent work has increasingly recognized that emotional vocalizations can color and shape interactions between individuals. Here we present data on the psychometric properties of a recently developed database of authentic nonlinguistic emotional vocalizations from human adults and infants (the Oxford Vocal 'OxVoc' Sounds Database; Parsons, Young, Craske, Stein, & Kringelbach, 2014). In a large sample (n = 562), we demonstrate that adults can reliably categorize these sounds (as 'positive,' 'negative,' or 'sounds with no emotion'), and rate valence in these sounds consistently over time. In an extended sample (n = 945, including the initial n = 562), we also investigated a number of individual difference factors in relation to valence ratings of these vocalizations. Results demonstrated small but significant effects of (a) symptoms of depression and anxiety with more negative ratings of adult neutral vocalizations (R2 = .011 and R2 = .008, respectively) and (b) gender differences in perceived valence such that female listeners rated adult neutral vocalizations more positively and infant cry vocalizations more negatively than male listeners (R2 = .021, R2 = .010, respectively). Of note, we did not find evidence of negativity bias among other affective vocalizations or gender differences in perceived valence of adult laughter, adult cries, infant laughter, or infant neutral vocalizations. Together, these findings largely converge with factors previously shown to impact processing of emotional facial expressions, suggesting a modality-independent impact of depression, anxiety, and listener gender, particularly among vocalizations with more ambiguous valence. (PsycINFO Database Record

Children’s Vocal Properties as Mobilizers of Stress-Related Physiological Responses in Adults

We measured the ways that women with varying degrees of perceived power respond physiologically to children’s elevated vocal pitch (F0 : fundamental frequency), a social dependence/immaturity cue. Listeners believed either that they would provide instructions or make judgments about the children they heard. As predicted, women with low perceived power in caregiving relationships (i.e., who attributed greater power to children than to self) were highly reactive to children’s pitch properties—in particular, when they anticipated providing instructions. When expecting to provide instructions to children with higher F0 voices, women with low perceived power showed elevations in cortisol levels and heart rate (consistent with defensive mobilization for threat). In all other pairings of women and children, cortisol and heart rate levels held relatively constant or declined. In addition, women with low perceived power showed better recall of messages from children with higher F0 voices than lower F0 voices. Implications are drawn for interaction patterns that foster caregiving stress and conflict.

Evidence for a Caregiving Instinct: Rapid Differentiation of Infant from Adult Vocalizations Using Magnetoencephalography

Crying is the most salient vocal signal of distress. The cries of a newborn infant alert adult listeners and often elicit caregiving behavior. For the parent, rapid responding to an infant in distress is an adaptive behavior, functioning to ensure offspring survival. The ability to react rapidly requires quick recognition and evaluation of stimuli followed by a co-ordinated motor response. Previous neuroimaging research has demonstrated early specialized activity in response to infant faces. Using magnetoencephalography, we found similarly early (100-200 ms) differences in neural responses to infant and adult cry vocalizations in auditory, emotional, and motor cortical brain regions. We propose that this early differential activity may help to rapidly identify infant cries and engage affective and motor neural circuitry to promote adaptive behavioral responding, before conscious awareness. These differences were observed in adults who were not parents, perhaps indicative of a universal brain-based "caregiving instinct."

The Power of an Infant's Smile: Maternal Physiological Responses to Infant Emotional Expressions

Infant emotional expressions, such as distress cries, evoke maternal physiological reactions. Most of which involve accelerated sympathetic nervous activity. Comparatively little is known about effects of positive infant expressions, such as happy smiles, on maternal physiological responses. This study investigated how physiological and psychological maternal states change in response to infants’ emotional expressions. Thirty first-time mothers viewed films of their own 6- to 7-month-old infants’ affective behavior. Each observed a video of a distress cry followed by a video showing one of two expressions (randomly assigned): a happy smiling face (smile condition) or a calm neutral face (neutral condition). Both before and after the session, participants completed a self-report inventory assessing their emotional states. The results of the self-report inventory revealed no effects of exposure to the infant videos. However, the mothers in the smile condition, but not in the neutral condition, showed deceleration of skin conductance. These findings demonstrate that the mothers who observed their infants smiling showed decreased sympathetic activity. We propose that an infant’s positive emotional expression may affect the branch of the maternal stress-response system that modulates the homeostatic balance of the sympathetic and parasympathetic nervous systems.

Motion and emotion: depression reduces psychomotor performance and alters affective movements in caregiving interactions

BACKGROUND

Impaired social functioning is a well-established feature of depression. Evidence to date suggests that disrupted processing of emotional cues may constitute part of this impairment. Beyond processing of emotional cues, fluent social interactions require that people physically move in synchronized, contingent ways. Disruptions to physical movements are a diagnostic feature of depression (psychomotor disturbance) but have not previously been assessed in the context of social functioning. Here we investigated the impact of psychomotor disturbance in depression on physical responsive behavior in both an experimental and observational setting.

METHODS

In Experiment 1, we examined motor disturbance in depression in response to salient emotional sounds, using a laboratory-based effortful motor task. In Experiment 2, we explored whether psychomotor disturbance was apparent in real-life social interactions. Using mother-infant interactions as a model affective social situation, we compared physical behaviors of mothers with and without postnatal depression (PND).

RESULTS

We found impairments in precise, controlled psychomotor performance in adults with depression relative to healthy adults (Experiment 1). Despite this disruption, all adults showed enhanced performance following exposure to highly salient emotional cues (infant cries). Examining real-life interactions, we found differences in physical movements, namely reduced affective touching, in mothers with PND responding to their infants, compared to healthy mothers (Experiment 2).

CONCLUSIONS

Together, these findings suggest that psychomotor disturbance may be an important feature of depression that can impair social functioning. Future work investigating whether improvements in physical movement in depression could have a positive impact on social interactions would be of much interest.

Testosterone administration modulates neural responses to crying infants in young females

Parental responsiveness to infant vocalizations is an essential mechanism to ensure parental care, and its importance is reflected in a specific neural substrate, the thalamocingulate circuit, which evolved through mammalian evolution subserving this responsiveness. Recent studies using functional Magnetic Resonance Imaging (fMRI) provide compelling evidence for a comparable mechanism in humans by showing thalamocingulate responses to infant crying. Furthermore, possibly acting on this common neural substrate, steroid hormones such as estradiol and testosterone, seem to mediate parental behavior both in humans and other animals. Estradiol unmistakably increases parental care, while data for testosterone are less unequivocal. In humans and several other animals, testosterone levels decrease both in mothers and fathers during parenthood. However, exogenous testosterone in mice seems to increase parenting, and infant crying leads to heightened testosterone levels in human males. Not only is the way in which testosterone is implicated in parental responsiveness unresolved, but the underlying mechanisms are fully unknown. Accordingly, using fMRI, we measured neural responses of 16 young women who were listening to crying infants in a double blind, placebo-controlled, counterbalanced, testosterone administration experiment. Crucially, heightened activation in the testosterone condition compared to placebo was shown in the thalamocingulate region, insula, and the cerebellum in response to crying. Our results by controlled hormonal manipulation confirm a role of the thalamocingulate circuit in infant cry perception. Furthermore, the data also suggest that exogenous testosterone, by itself or by way of its metabolite estradiol, in our group of young women acted on this thalamocinculate circuit to, provisionally, upregulate parental care.

Effects of motherhood on physiological and subjective responses to infant cries in teenage mothers: a comparison with non-mothers and adult mothers

The present study was designed to determine whether becoming a mother during the adolescent period changes maternal responsiveness or maternal motivation, assessed through hormonal, autonomic, and hedonic responses to recorded infant cries and interactions with their babies. Fifty-six teen mothers were compared to 58 teen non-mothers and 49 adult mothers. Teen mothers reported more sympathy and alertness in response to recorded infant cries compared to non -mother teens; however, among the teen women there were no differences between mothers and non-mothers in heart rate and cortisol responses to infant cries. In contrast, in comparison to adult mothers, teen mothers reported the same levels of sympathy and alertness to infant cries; however, adult mothers showed an 'alerted' pattern of heart rate and cortisol response to infant cries not seen in the teen mother group. Inclusion of the covariate, fathers' employment classification as an index of SES or time of testing and cortisol sampling did not affect this pattern of results. Taken together, these results show that where self-report is used as a measure of maternal responsiveness, teen mothers are no different in responsiveness than adult mothers; however, where physiological and interactional measures of responsiveness are considered, teen mothers are less likely to show heightened or selective responses to infant cries or respond 'attentively' to the infant.

Sex differences in the preattentive processing of vocal emotional expressions

Emotional tone of voice indicates the significance of a spoken utterance. We asked whether listeners recognize this significance even when attending to something else and whether men and women differ in this regard. To answer these questions, we presented emotionally or neutrally spoken syllables as standards and deviants in a mismatch negativity paradigm. Independent of the listeners' sex, deviants elicited a mismatch negativity in the scalp-recorded event-related potential as an indicator of preattentive acoustic change detection. Only women, however, showed a larger mismatch negativity to emotional than to neutral deviants. Thus, even though both sexes detect change in voice preattentively, only women recruit additional processing resources when the change in voice is one of emotional valence.

Measuring stress responses in postpartum mothers: perspectives from studies in human and animal populations

Reduced hypothalamic-pituitary-adrenal (HPA) responses to stress during the last week of pregnancy and lactation have been consistently observed in rat studies. Several contributing factors have been proposed for this phenomenon in lactation, including the suckling stimulus from the pups, hormones (oxytocin and prolactin) and opioids, a decrease in the ability of noradrenaline to potentiate hypothalamic responses and changes in pituitary responsiveness to ACTH secretagogues (AVP and CRF). In contrast to this vast literature using the rat model, only few studies have addressed this issue in the human population. The consensus is that women engaging in breastfeeding activities exhibit reduced anxiety, although the reductions in neuroendocrine and autonomic responses to stressors are variable, in part because of the different nature of the stressors used. Further work is required to investigate how additional factors, such as maternal parity or emotional salience of the stressor can affect stress responsiveness in postpartum women. Here, we review first the findings regarding stress responsiveness during lactation in both rat and human studies, and then discuss potential research avenues and methodological issues that could be the lead to future research protocols in human subjects. Knowing the reciprocal relationship in the mother-infant dyad, it is clear that investigation of the mechanisms regulating stress responses and mental health in postpartum mothers can only be beneficial to the development of the infant.