Inverse Response Function in Infants

[By: Iara de Almeida Ivo]

The physiological reaction to neural activity is modulated by neurometabolic and neurovascular coupling. Increased neural activity triggers an increase in oxygen delivery to the active region a few seconds later.

Figure 1 – Neurovascular Coupling mechanism schematic. Adapted from Schölkman et al.

This reaction can be modulated by measuring the oxygenated haemoglobin and deoxyhaemoglobin expected relative concentration changes in relation to an event in relation to the known canonical model for the haemodynamic response.

Figure 2 – Representation of the Canonical Haemodynamic Response, adapted from Schölkman et al.

Models of this reaction have been created, alike the one in figure (2), from empirical data for adults. Infant studies however, sometimes refer to what came to be known as a IRF or Inverse Response Function, for certain tasks – figure (3).

Figure 3 – IRF adapted from Issard et al.


The rationale behind this effect relates to the maturation of the brain, the hemodynamic response increasingly often takes on a canonical shape. This because the known hemodynamic response relies on a complex interaction between the vascular system, neurons and glial cells, all of which undergo considerable maturation throughout infancy. However, since brain maturation is not homogenous between cortical regions, the hemodynamic response may vary from one brain area to another.

If we decompose each of these systems, in order to take a closer look at known metrics.

Grey matter develops most of its volume until the third year of age and in terms of blood supply, it is labelled that for one year old infants the average CMRO2 (Cerebral metabolic rate of oxygen) was 38.3±17.7 μmol/100g/min and was positively correlated with age (p=0.007, slope 5.2 μmol/100g/min per week), although the highest CMRO2 value in this age range was still less than half of the adult level.  (Liu et al. & Solokov et al)

The Cerebral blood volume CBV and Oxygen Saturation Percentage are alto quite variable, not only for infants but also for different cortical structures in same age group infants. (Franceschini et al).

Figure 4 – Cerebral Blood Volume in ml/100gm and Oxygen Saturation Percentages for frontal, occipital, temporal and parietal cortical regions for 6 age groups, adapted from Franceschini et al.

This leads to different proportions and in-homogeneity, depending on age and brain region.

However, inter subject differences do not end there, task difficulty depending on brain region is also relevant parameter to consider.

In conclusion, data baseline adapted and specific to paradigm is even more relevant for Infancy studies, given the inter-subject, inter-cortical structure and task subjective variability of responses. We recommend before the beginning of any functional infancy study, taking a look at the review from Issard et al 2018, which covered over 20 years of infancy reported inverse responses, both in fNIRS and BOLD MRI, assessing that:

“The temporal cortex seems to present canonical responses earlier than the occipital and frontal cortices, and follows a more linear developmental trajectory than the occipital cortex. This latter shows a canonical response at birth, but an inverted response later in infancy.

Finally, the frontal cortex shows more variable responses, depending on stimulus complexity and age of participants. Social stimuli, such as speech and faces, elicit canonical responses earlier than non-social stimuli (such as fruits or flashing lights).”

Scholkmann, F., Kleiser, S., Metz, A. J., Zimmermann, R., Pavia, J. M., Wolf, U., & Wolf, M. (2014). A review on continuous wave functional near-infrared spectroscopy and imaging instrumentation and methodology. Neuroimage, 85, 6-27.

Issard, C., & Gervain, J. (2018). Variability of the hemodynamic response in infants: Influence of experimental design and stimulus complexity. Developmental cognitive neuroscience, 33, 182-193.

Liu, P., Huang, H., Rollins, N., Chalak, L. F., Jeon, T., Halovanic, C., & Lu, H. (2014). Quantitative assessment of global cerebral metabolic rate of oxygen (CMRO2) in neonates using MRI. NMR in biomedicine, 27(3), 332-340.

Sokoloff, L. (1960). The metabolism of the central nervous system in vivo. Handbook of physiology, section I, neurophysiology, 3, 1843-1864.

Franceschini, M. A., Thaker, S., Themelis, G., Krishnamoorthy, K. K., Bortfeld, H., Diamond, S. G., … & Grant, P. E. (2007). Assessment of infant brain development with frequency-domain near-infrared spectroscopy. Pediatric research, 61(5), 546-551.

In lullabies, all magic flows

[By: Aude Carteron]

Infant-directed song (the academic word for lullaby), is a common way to soothe, calm or put babies to sleep. It is found universally across cultures [1].

Babies are little Beethoven-to-be, born with remarkable music perception abilities. A study [2] with neonates revealed that the latter can detect the regularity of beats: recording of their brain activity showed that a particular brain signal was elicited at the time when downbeats were missing.

Read moreIn lullabies, all magic flows

3 things to know about this brain cap (or EEG, or electroencephalogram)

[By: Sayaka Kidby]

When visiting our babylab in Lancaster, some people say, “I’m here to do a study with a cap like a jellyfish”. Then I know they are here for my study. Yes, I use this jellyfish cap, called EEG (or electroencephalogram, to be more precise), to monitor baby’s brain activity.

A cap which monitors brain activity sounds cool – but what exactly does it do? When was it invented, by whom, and what can it tell us? In this month’s blog, I’ll talk about three things about EEG, as well as three reasons we should be bothered to measure brain activities despite all the challenges to get good data from cheeky little ones.

Read more3 things to know about this brain cap (or EEG, or electroencephalogram)

Study Update – Prosocial Development preliminary findings

[By: Victoria Licht]

For almost a year now I have been working on a study looking at prosociality in infants, specifically the development and their degree of understanding within it. At a young age, 3 months old, infants already display a strong preference for prosocial individuals over antisocial ones (Hamlin et al., 2007; Hamlin & Wynn, 2011). In this study we are investigating the role of individual differences in promoting and shaping understanding of prosocial and antisocial events. We evaluated 5 to 6-month-old infants in their ability to discriminate and prefer prosocial over antisocial individuals using several different methods ERP/EEG, behavioral measures (looking times and manual choice task), and we investigated through questionnaires whether temperament (Rothbart, 1981) and attachment (Condon et al., 2008) styles would affect the emergence of this ability. In total 26 infants were tested and analyzed in the behavioral measures; 7 infants achieved the sufficient number of trails per condition to be included in the ERP analysis.

Read moreStudy Update – Prosocial Development preliminary findings

Baby comedians, grown-up clowns

[By: Pinelopi Bounia Mastrogianni]

Our adult, (not always) sophisticated sense of humour might involve laughing at Epic-Cat-Fails videos on the internet or at very bad puns, but do you remember that period when the re-appearance of mum’s face with a “peek-a-boo” was the best joke in the world? Probably not, but it was a fascinating one! Babies start laughing before they start to crawl, walk or talk and, before long, they start producing their very own non-verbal jokes to make people around them laugh. They start smiling at their first month and they laugh for the first time around 4-5 months of age, while they begin a humorous interaction by their 7-8 months. This very early adorable behaviour is proposedly connected to general cognitive development, as well as to the quality of the bond between infants and their caregivers – thus researchers have tried to describe the different ways infants joke and, mainly, what are the things they find amusing.

Read moreBaby comedians, grown-up clowns

Training school in Gothenburg

[By: Clément Dardenne]

From Monday 14th October to Friday 18th 2019, the ESRs (Early Stage Researchers) of the MOTION project gathered in Gothenburg for the last training school of 2019. My company, Smart Eye, was in charge of hosting the event, and I wanted to start this blog article by thanking Karin Persson and Jörgen Thaung for their devotion and the awesome organization of this week.

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Replication Crisis in Psychology Research: Who’s to Blame for?

[By: Umay Șen]

As a part of my PhD program, I am attending a lot of classes besides doing research. Recently, I took the course on Bayesian Statistics and had a lot of chance to compare Bayesian approach to data and statistical analysis to the frequentist approach which is/was more common in the field. This course made me get a critical perspective to the frequentist approach which is one of the most common practices in Psychology when you deal with the data. In this blog post, I would like to share some basic ideas of Bayesian approach and discuss it in relation to the replication crisis in Psychology.

Read moreReplication Crisis in Psychology Research: Who’s to Blame for?

Sharing our research

[By: Joanna Rutkowska]

As ESRs in MOTION, funded by the European Union, we have a duty to disseminate our research findings as much as possible. There are several ways of doing so, and different audiences that we can present to. Firstly, one can present the research to the lawmakers and politicians in hopes of influencing future policies and governmental plans. Unfortunately, only few of the scientists are ever invited to do so, and they are definitely not PhD candidates, but rather respectable professors! Secondly, one can present their research to the (wider) public – everyone from parents to children themselves. I believe this is the best way to get everyone interested in research and try to make a change on a societal level bottom-up.

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Learning is a fundamental activity for children (and for ESRs as well!)

[By: Valentina Barone]

By the time you are hired as a researcher everyone expects you to be an expert. There’s no way you would get that position if you weren’t smart enough, right? Researchers – also the early stage ones – are supposed to show a high level of expertise and trustworthiness, associated with multiple skills like initiative and independence. A self-standing person who is able to dive into the intricate ocean of science and who can return to the surface with extraordinary results to share with the mainland. It sounds so fancy and respectful to read the initials “PhD” beside someone’s name. “Yes, I must definitely own enough competence if I got to this point, as a PhD candidate I am part of an intellectual élite after all”. This is what I sometimes tell myself in one of the rare excess of self-esteem I have.

Read moreLearning is a fundamental activity for children (and for ESRs as well!)