Recovering Wood and McCarthy’s ERP-prototypes by means of ERP-specific procrustes-rotation
•Conventional rotation methods fail to recover Wood and McCarthy’s prototypes.•Conventional rotations result in a substantial amount of variance misallocation.•Two new rotation-methods based on ERP-characteristics are proposed.•The new rotation-methods need no a priori knowledge on treatment-effects...
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Published in | Journal of neuroscience methods Vol. 295; pp. 20 - 36 |
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Main Author | |
Format | Journal Article |
Language | English |
Published |
Netherlands
Elsevier B.V
01.02.2018
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Subjects | |
Online Access | Get full text |
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Summary: | •Conventional rotation methods fail to recover Wood and McCarthy’s prototypes.•Conventional rotations result in a substantial amount of variance misallocation.•Two new rotation-methods based on ERP-characteristics are proposed.•The new rotation-methods need no a priori knowledge on treatment-effects.•The new rotation-methods: reduce variance misallocation.
The misallocation of treatment-variance on the wrong component has been discussed in the context of temporal principal component analysis of event-related potentials. There is, until now, no rotation-method that can perfectly recover Wood and McCarthy’s prototypes without making use of additional information on treatment-effects.
In order to close this gap, two new methods: for component rotation were proposed. After Varimax-prerotation, the first method identifies very small slopes of successive loadings. The corresponding loadings are set to zero in a target-matrix for event-related orthogonal partial Procrustes- (EPP-) rotation. The second method generates Gaussian normal distributions around the peaks of the Varimax-loadings and performs orthogonal Procrustes-rotation towards these Gaussian distributions. Oblique versions of this Gaussian event-related Procrustes- (GEP) rotation and of EPP-rotation are based on Promax-rotation.
A simulation study revealed that the new orthogonal rotations recover Wood and McCarthy’s prototypes and eliminate misallocation of treatment-variance. In an additional simulation study with a more pronounced overlap of the prototypes GEP Promax-rotation reduced the variance misallocation slightly more than EPP Promax-rotation.
Comparison with Existing Method(s): Varimax- and conventional Promax-rotations resulted in substantial misallocations of variance in simulation studies when components had temporal overlap. A substantially reduced misallocation of variance occurred with the EPP-, EPP Promax-, GEP-, and GEP Promax-rotations.
Misallocation of variance can be minimized by means of the new rotation methods: Making use of information on the temporal order of the loadings may allow for improvements of the rotation of temporal PCA components. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0165-0270 1872-678X |
DOI: | 10.1016/j.jneumeth.2017.11.011 |