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Published on: February 15, 2014
Optimizing stimulation and analysis protocols for neonatal fMRI
Rhodri Cusack1, Conor Wild2, Annika C Linke2
1Brain and Mind Institute, Western University, London, Canada; Children's Health Research Institute, London, Canada.
Insights
Neonatal fMRI is crucial for understanding infant brain development. Optimizing stimulation protocols and using age-appropriate hemodynamic response functions (HRF) significantly enhances the power and accuracy of these brain imaging studies.
Area of Science:
- Neuroscience
- Developmental Biology
- Medical Imaging
Background:
- Infant brain development is complex and challenging to study due to limited behavioral expression.
- Functional magnetic resonance imaging (fMRI) offers potential for characterizing typical and abnormal infant brain development.
- Neonatal fMRI faces methodological challenges, particularly differences in the hemodynamic response function (HRF) compared to adults.
Purpose of the Study:
- To address methodological challenges in neonatal fMRI by investigating the impact of HRF differences.
- To optimize fMRI stimulation protocols and analysis for improved sensitivity and robustness in infant studies.
- To assess the effect of HRF modeling on the power of different stimulation protocols in neonatal fMRI.
Main Methods:
- Developed a realistic noise model using resting-state fMRI data from infants and adults.
- Conducted simulations to evaluate the influence of HRF on stimulation protocols and analysis assumptions.
- Investigated the efficacy of using age-appropriate HRF versus mismatched HRF during data analysis.
Main Results:
- Neonatal fMRI is most powerful with shorter block durations (25-30s on/off cycle).
- Using age-appropriate HRF is critical; mismatches reduce statistical power or invert the signal.
- A flexible basis set approach performs well when the exact HRF is unknown, enabling accurate post-hoc estimation.
Conclusions:
- Optimized stimulation protocols and HRF modeling are essential for robust and sensitive neonatal fMRI.
- Employing age-specific HRF or flexible basis sets improves the reliability of fMRI findings in infants.
- These advancements facilitate better characterization of typical and abnormal infant brain development using fMRI.
Abstract:
The development of brain function in young infants is poorly understood. The core challenge is that infants have a limited behavioral repertoire through which brain function can be expressed. Neuroimaging with fMRI has great potential as a way of characterizing typical development, and detecting abnormal development early. But, a number of methodological challenges must first be tackled to improve the robustness and sensitivity of neonatal fMRI. A critical one of these, addressed here, is that the hemodynamic response function (HRF) in pre-term and term neonates differs from that in adults, which has a number of implications for fMRI. We created a realistic model of noise in fMRI data, using resting-state fMRI data from infants and adults, and then conducted simulations to assess the effect of HRF of the power of different stimulation protocols and analysis assumptions (HRF modeling). We found that neonatal fMRI is most powerful if block-durations are kept at the lower range of those typically used in adults (full on/off cycle duration 25-30s). Furthermore, we show that it is important to use the age-appropriate HRF during analysis, as mismatches can lead to reduced power or even inverted signal. Where the appropriate HRF is not known (for example due to potential developmental delay), a flexible basis set performs well, and allows accurate post-hoc estimation of the HRF.
