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Abstract
The variability inherently present in biophysical data is partly contributed by disparate sampling resolutions across instrumentations. This poses a potential problem for statistical inference using pooled data in open access repositories. Such repositories combine data collected from multiple research sites using variable sampling resolutions. One example is the Autism Brain Imaging Data Exchange repository containing thousands of imaging and demographic records from participants in the spectrum of autism and age-matched neurotypical controls. Further, statistical analyses of groups from different diagnoses and demographics may be challenging, owing to the disparate number of participants across different clinical subgroups. In this paper, we examine the noise signatures of head motion data extracted from resting state fMRI data harnessed under different sampling resolutions. We characterize the quality of the noise in the variability of the raw linear and angular speeds for different clinical phenotypes in relation to age-matched controls. Further, we use bootstrapping methods to ensure compatible group sizes for statistical comparison and report the ranges of physical involuntary head excursions of these groups. We conclude that different sampling rates do affect the quality of noise in the variability of head motion data and, consequently, the type of random process appropriate to characterize the time series data. Further, given a qualitative range of noise, from pink to brown noise, it is possible to characterize different clinical subtypes and distinguish them in relation to ranges of neurotypical controls. These results may be of relevance to the pre-processing stages of the pipeline of analyses of resting state fMRI data, whereby head motion enters the criteria to clean imaging data from motion artifacts.
Highlights
The advent of open-access data repositories across various scientific fields has initiated new avenues with the potential for transformative discoveries
The variable degree of skewness we have previously found in the empirical distributions of linear and angular speed peaks derived from these ABIDE data (Torres et al, 2017) sets motivated us to further explore the possibility that different random processes may underlie the time series data collected under different sampling resolution (SR)
This paper addressed the question of whether the disparity in sampling resolution across different sites in the ABIDE repository would affect the quality of the noise-to-signal ratios empirically derived from the fluctuations in the amplitude of head motion speed
Summary
The advent of open-access data repositories across various scientific fields has initiated new avenues with the potential for transformative discoveries. It is possible to aggregate data from different sites and attain a very large number of subjects to build normative data sets from typical controls, as well as to examine pathologies of the nervous systems in relation to new standardized normative scales. Such new characterizations of mental illnesses respond to a recent paradigm shift in psychiatry neuroscience whereby neurodevelopmental disorders are conceptualized as precursors of mental disorders (e.g., schizophrenia and related mental illnesses) emerging later in life (Paus et al, 2008; Insel, 2009, 2010; Casey et al, 2014)
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