Measuring energy metabolism during functional activation in the infant brain

• In Event: Poster Session 10
  In Poster Session: PS 10 Topic - Biological Processes: Neuroscience and Genetics

Abstract

Over the last few decades, the use of neuroimaging techniques has being increasingly employed in neurodevelopmental research to investigate specialisation of brain function. Typically, functional near-infrared spectroscopy (fNIRS) measures changes in blood oxygenation, related to underlying neural activity, but provides indirect measures of neuronal activation. To date, less work in the field of neurodevelopmental research has focused on investigating how the coupling of neural activity and blood oxygenation develops in infancy and how that may impact specialisation of brain function. Broadband NIRS (bNIRS) provides the opportunity to investigate this relationship through the measurement of changes in the oxidation state of mitochondrial respiratory chain enzyme cytochrome-c-oxidase (oxCCO) thereby providing measures of cerebral energy metabolism alongside haemodynamic changes (Siddiqui et al., 2017). The aim of the study presented here was to use bNIRS to measure changes in cerebral energy metabolism, alongside blood oxygenation changes, in the social brain regions in infants.

42 typically developing (TD) infants aged between 4 and 7 months were studied. The infants wore custom-built bNIRS headgear with 9 channels located over the right hemisphere. The bNIRS system was developed at UCL (Phan et al., 2016) and 120 wavelengths between 780-900nm were used to convert the change in attenuation of light to the changes in concentration of HbO2 (Δ[HbO2]), HHb (Δ[HHb]) and oxCCO (Δ[oxCCO]). The experimental stimuli consisted of two conditions; 1) social and 2) non-social visual and auditory stimuli. Following initial processing steps, the valid trials for each infant were averaged to obtain an average time-course for each channel. Data from infants with a valid number of channels and trials were averaged to obtain a grand-averaged response which is shown in Figure 1 for (a) the social condition and (b) the non-social condition. For statistical analysis, a time-window of 10-18s post-stimulus onset was selected to identify the maximum change in concentration of HbO2, HHb and oxCCO. Image reconstruction (Brigadoi et al.,2017) was performed at the individual subject level and images were projected onto the mesh of an infant head model.

A significant difference was found between the conditions for Δ[oxCCO], Δ[HbO2] and Δ[HHb] over the temporo-parietal region, in accordance with results from previous studies (Lloyd-Fox et al., 2009). Figure 2 shows the reconstructed images from an individual infant at three time points and in accordance with the time-course data shown in Figure 1 and shows the capability of the image reconstruction analysis.

The results from this study provide the first spatially resolved measures of mitochondrial activity during functional activation in infants. This study sheds light on neurometabolic pathways in early infancy, thereby aiding our understanding of brain development.

Authors

• Maheen Faisal Siddiqui, Birkbeck University of London
  Presenting Author

• Emily J.H. Jones, Birkbeck, University of London
  Non-Presenting Author

• Sarah Lloyd-Fox, Birkbeck, University of London
  Non-Presenting Author

• Liam Collins-Jones, UCL
  Non-Presenting Author

• Sabrina Brigadoi, University of Padova
  Non-Presenting Author

• Ilias Tachtsidis, UCL
  Non-Presenting Author

• Mark H. Johnson, University of Cambridge
  Non-Presenting Author

• Clare Elwell, University College London
  Non-Presenting Author