On the Temporal Characteristics of Performance Variability in Attention Deficit Hyperactivity Disorder ADHDReport as inadecuate




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Increased intra-subject variability of reaction times ISV-RT is one of the most consistent findings in attention-deficit-hyperactivity disorder ADHD. Although the nature of this phenomenon is still unclear, it has been hypothesised to reflect interference from the Default Mode Network DMN. So far, ISV-RT has been operationally defined either as a frequency spectrum of the underlying RT time series, or as a measure of dispersion of the RT scores distribution. Here, we use a novel RT analysis framework to link these hitherto unconnected facets of ISV-RT by determining the sensitivity of different measures of RT dispersion to the frequency content of the underlying RT time series. N=27 patients with ADHD and N=26 healthy controls performed several visual N-back tasks. Different measures of RT dispersion were repeatedly modelled after individual frequency bands of the underlying RT time series had been either extracted or suppressed using frequency-domain filtering. We found that the intra-subject standard deviation of RT preserves the -1-f noise- characteristic typical of human RT data. Furthermore and most importantly, we found that the ex-Gaussian parameter τ is rather exclusively sensitive to frequencies below 0.025 Hz in the underlying RT time series and that the particularly slow RTs, which nourish τ, occur regularly as part of an quasi-periodic, ultra-slow RT fluctuation. Overall, our results are compatible with the idea that ISV-RT is modulated by an endogenous, slowly fluctuating process that may reflect DMN interference.



Author: Bernd Feige, Monica Biscaldi, Christopher W. N. Saville, Christian Kluckert, Stephan Bender, Ulrich Ebner-Priemer, Klaus Hennigha

Source: http://plos.srce.hr/



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