Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - FATHER TRIALS (Father Trials: Hormonal and Behavioral Experiments on Prenatal and Postnatal Parenting )

Teaser

Fathers have largely been neglected in parenting research -- although they constitute about 50% of parents. In the current project we test the hypothesis that fathers’ parenting is affected by their hormonal levels, and can be changed by behavioral and hormonal...

Summary

Fathers have largely been neglected in parenting research -- although they constitute about 50% of parents. In the current project we test the hypothesis that fathers’ parenting is affected by their hormonal levels, and can be changed by behavioral and hormonal interventions. Experiments that modulate fathers’ hormonal levels are expected to modulate their neural processing of infant signals and of threats to the infant, and to stimulate fathers’ parenting quality and involvement in parenting.

The way parents treat their young infants is of major importance, as for example shown by ‘an experiment in zero parenting’, that describes long-term harm in Romanian orphans (Science, August 2014). In animals, parenting is under strong hormonal control, and it would be naïve to suppose that this is very different for human parents. Nevertheless, parenting intervention studies aimed at enhancing the quality of parenting behavior hardly ever examine the effects of interventions on parents’ hormonal levels. The mechanisms of successful interventions remain a closed book. The persistence of intervention effects on parenting behavior, however, strongly suggests that parents change ‘under the skin’. Thus, a gap exists in the research. On the one hand, trials have tested the effects of steroid and peptide administration on aspects of parenting that include neural processing of infant signals, on the other hand, trials involving parents, usually mothers, have tested the efficacy of behavioral interventions in realizing more sensitive parent-child interaction but without studying the neurobiological mechanisms.

This project bridges the gap by combining two types of RCTs (within-subject and between-subject trials) and two types of experiments (hormonal administration and behavioral intervention), in a critical phase of parenthood: the transition to having the first baby. The focus lies on the 50% of parents who have tended to be neglected in research, where ‘parenting’ is often equivalent to ‘mothering’, and –until recently- have also been neglected in family policies: fathers. The fact that in most families the participation of fathers in child rearing is modest does not necessarily mean that their parental role is irrelevant for child development, or that this role is carved in stone and resistant to change. There is an urgent need for greater insight into the hormonal and behavioral dynamics of the paternal role.

In research on parenting, quality parental sensitivity is a key construct. It refers to the ability to attend to infant signals and to respond promptly and appropriately. Higher levels of parental sensitivity predict more favorable child outcomes, irrespective of cultural or socio-economic context, both in fathers and mothers. However, studies have consistently shown that fathers are less sensitive towards their infants and toddlers than mothers, although seeing infants has similar motivational salience to men and women. In most western countries fathers have increased their participation in parenting over the past decades, but maternal involvement remains substantially higher. Fathers spend on average less than half as much time in direct one-on-one interaction with their children as mothers, especially in early childhood. Although the quantity of time invested in parenting is generally considered less important than quality (“quality time”), it is easy to see that it takes considerable time to get to know an infant, become aware of its preferences, and read its signals. For most young fathers, spending more time in interaction with their infant will add to the quality of the interaction.

Sensitive parenting starts with the processing of infant signals, which in turn is affected by hormonal levels, at least in females. These hormones probably play a role in fathers’ processing of infant signals as well, but the direction of the association is as yet unclear. Once infant signals have been proce

Work performed

Progress has been made in the following domains:
1. Two PhDs (Lotz, Van Dijk) and four postdocs (Van ‘t Veer, Meijer, Thijssen, Rijlaarsdam) were hired. One of the PhDs (Van Dijk) and one of the postdocs were accounted for by cofinancing. In addition, I secured 23.4 hours per week from a postdoc with experience in designing fMRI tasks with auditory stimuli (Witteman). Marinus van IJzendoorn (cofinanced) has supported the team as consultant in all phases of the project.
2. Literature reviews were written on the role of oxytocin in parenting (Feldman & Bakermans-Kranenburg, 2017; Van IJzendoorn & Bakermans-Kranenburg, 2016) and on protective parenting (Bakermans-Kranenburg & Van IJzendoorn, 2017, in press). A series of papers on parenting (Rijlaarsdam et al., 2016; Thijssen et al., 2017), oxytocin experiments (Mah et al., 2016; Riem et al., 2017), and exposure to infant signals (Heckendorff et al., 2016; Riem et al., 2017) were written or completed, and invited lectures on fathering and video feedback intervention were given.
3. Two systematic reviews have been initiated: one on the association between testosterone and parenting (Meijer), and one of neuroimaging studies of infant cry perception (Witteman).
4. Paradigms to be used in the pretest, posttest, and follow-up assessments were developed, and scenarios for each of these assessments were written. The app for ambulatory measurement of paternal involvement was developed. For the fMRI tasks brief video vignettes displaying non-threatening situations (e.g., baby in buggy on quay), and threatening situations (e.g., baby in buggy tumbling from quay into the water) have been made by a professional film producer.
5. Recruitment strategies have been developed and tested, in particular for recruitment of fathers before the birth of their first infants, where we cannot rely on birth registers. A Dutch website has been launched, presentations on young parents events have been given, and contacts have been established with midwifes and organizers of pregnancy courses and ‘daddy-classes’.
6. Because nasally administrated testosterone turned out to be no longer available, we searched for a valid and feasible alternative. Testosterone gel was excluded for two reasons: (a) using the gel would reveal the condition, abolishing the double-blindness of the experiment, and (b) the gel would not without risk for their pregnant partners. Vasopressin (AVP) was selected as an adequate alternative, because it (indirectly) increases testosterone levels and can be intranasally administered. The necessary administrative procedures for customs were followed in collaboration with the university hospital pharmacist, and approval of the Ethics committee was obtained.
7. A pilot study (N = 25) has been conducted involving fathers in the prenatal phase, with vasopressin and oxytocin administration in a within-subject design, and a follow-up with placebo administration after the birth of their infant. Approval from the local ethics committees (Institute of Education and Child Studies; Leiden University Medical Centre) was obtained for this pilot study. It enabled us to try out and improve our recruitment strategies, test the paradigms used in the pretest, posttest, and follow-up assessments, get experience with the administration of Vasopressin, and receive feedback on our procedures, instructions, and reward strategies. First results are presented below.
8. The procedures and results of the prenatal assessments were presented and discussed at the meeting with the International Advisory Board on 16 December 2016 (attending: prof dr Paul Ramchandani, prof dr Serge Rombouts, prof dr Eveline Crone, prof dr James Rilling, and the complete Father Trials team). The program of the day has been attached (see Figure 1). As a result of the discussions, some of the paradigms were adapted, and some coding strategies and analytic decisions were refined.
9. A manual on the use a “B0 map” scan to correct for di

Final results

Modulation of the paternal neural response to threat by vasopressin has been examined using three different neuroimaging paradigms.
(1) Our first results point to differential brain responses to threatening versus non-threatening video vignettes of situations with babies involved. For the first time video vignettes have been used to indicate threat to an infant, largely increasing the ecological validity of the measures. Already before the birth of their baby, fathers show stronger brain responses (in the precentral gyrus, superior frontal gyrus, juxtapositional lobule cortex and the opercular cortex) to threatening situations when they have been prompted with a morphed baby image with physical similarity to themselves (compared to an unfamiliar baby image). See Figure 2.
(2) Our results also suggest that fathers show a stronger brain response to infant cry sounds compared to scrambled control sounds (in left and right auditory cortex, and posterior cingulate cortex and precuneus, see Figure 3). Moreover, AVP administration increased the neural response to the same cry sounds presented with emotional context information (i.e., ‘this child is sick’, and ‘this child is bored’) compared to the same cry sounds presented with neutral context information (i.e., ‘this is an infant’) in a cluster including the cerebellum, precuneus, posterior cingulate cortex, brainstem, lingual gyrus, fusiform cortex parahippocampal gyrus, and hippocampus, as well as in a cluster including the putamen, insula, and central opercular cortex (Figure 4).
(3) In a working memory task fathers had to keep active in working memory either one (low load) or five (high load) letters while infant cries or control sounds were presented. Hence this task measured relatively attention independent of neural processing of stimuli that may signal threat to the infant (i.e. cries), allowing us to test whether hormones modulate this relatively ‘automatic’ paternal processing of threat signals. Preliminary pilot results indicate that vasopressin indeed modulates such automatic processing of infant cries by affecting activity in the inferior parietal lobule.

Not only neural processing of stimuli that signal threat to the infant may be modulated by hormones but also fathers’ cognitive-emotional and behavioral parenting-related responses. Humans’ primary mode of communication is language, but hormonal modulation of parental linguistic processing has not been examined yet. Therefore we asked fathers participating in the pilot some open questions about their future child and recorded 5 minutes of their speech which was subsequently transcribed to text. We hypothesized that if hormones would affect paternal linguistic processing, primarily the emotional content of the utterances would be affected. Therefore we used a sentiment analysis algorithm to test whether paternal utterances were affected by vasopressin administration. The results indicated that the transcripts were reliable and fathers’ utterances about their future child were highly positive. However, vasopressin did not affect the emotional content of paternal utterances.

Lastly, results of the pilot study point to differential behavioral responses to infant crying dependent on whether the fathers have been prompted with a morphed baby image with physical similarity to themselves or an image of an unfamiliar baby. Handgrip dynamometer force has previously been used as an index of excessive force in pseudo-parenting contexts. Participants are asked to squeeze a handgrip dynamometer as hard as possible, thus setting their own baseline, and then at 50% of their maximal handgrip strength. They perform as many trials as necessary for training, with their performance displayed on a monitor. Participants are then requested to squeeze the handgrip dynamometer at full and half strength without receiving feedback, while listening to infant crying and while listening to a scrambled sound acoustically simi

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