Measuring and diagnosing unilateral neglect: a standardized statistical procedure. Issue 6 (3rd October 2017)

• Record Type: Journal Article
• Authors: Toraldo, Alessio; Romaniello, Cristian; Sommaruga, Paolo
• Is Part Of: Clinical neuropsychologist. Volume 31:Issue 6/7(2017)
• Page Start: 1248
• Page End: 1267
• Publication Date: 2017-10-03
• Subjects: Unilateral neglect -- diagnosis -- cancellation -- visual search -- Mean Position of Hits; MPH, Mean Position of Hits -- MPO, Mean Position of Omissions -- MPT, Mean Position of Targets -- MOH, Mean Ordinal position of Hits -- MdnPH, Median Position of Hits -- FPR, false positive rate (α probability of type-I error) -- FNR, false negative rate (β probability of type-II error) -- LCR-adjusted, Left-Center-Right-adjusted -- C-adjusted, Center-adjusted (or centered) -- CoC, Center of Cancellation -- SD, expected standard deviation of MPH (unless otherwise stated) -- BF, Bayes Factor -- H, number of Hits -- T, number of targets -- G, number of target clusters -- FA, False Alarm (on catch trials) -- CR, Correct Rejections (on catch trials).; Neuropsychology -- Periodicals; Neuropsychology -- Periodicals; Mental Disorders -- Periodicals; 612.805
• DOI: 10.1080/13854046.2017.1349181
• Languages: English
• ISSNs: 1385-4046

Abstract

Abstract: Objective: Unilateral neglect is usually investigated by adminstering stimuli (targets) in different positions, with targets being responded to by the patient (Hit) or omitted. In spite of this homogeneity of data type, neglect indices and diagnostic criteria vary considerably, causing inconsistencies in both clinical and experimental settings. We aimed at deriving a standard analysis which would apply to all tasks sharing this data form.Methods: A-priori theoretical reasoning demonstrated that the mean position of Hits in space (MPH) is an optimal index for correctly diagnosing and quantifying neglect. Crucially MPH eliminates the confounding effects of deficits that are different from neglect (non-lateral) but which decrease Hit rate. We ran a Monte Carlo study to assess MPH's (so far overlooked) statistical behavior as a function of numbers of targets and Hits.Results: While average MPH was indeed insensitive to non-lateral deficits, MPH's variance (like that of all other neglect indices) increased dramatically with increasing non-lateral deficits. This instability would lead to alarmingly high false-positive rates (FPRs) when applying a classical diagnostic procedure that compares one patient with a control sample. We solved the problem by developing an equation that takes into account MPH instability and provides correct cut-offs and close-to-nominal FPRs, even without control subjects. We developed a computerized program which, given the raw data, yields the MPH, a z -score and a p -value.Conclusions: We provided a standard method that allows clinical and experimental neuropsychologists to diagnose and measure neglect in a consistent way across the vast majority of tasks.