We were thus unable to determine within-task variance, and fully acknowledge the limitations of this data set in demonstrating the proper consideration of within and between task variance.
Previously, it has also been suggested that co-variation between different control variables can be exploited to reduce task variance [81 86], for example, when deviations of two variables compensate for each other, as has been observed for variations in body and pistol angles compensating for each other to achieve a steady pointing position [81,82].
Our aim was to investigate various data transformations that could be applied before training the SVM to retain task discriminatory variance while suppressing irrelevant components of variance.
For instance, it has been demonstrated in simulated data and in a visual fMRI experiment that correlations varied depending on whether task-related variance, block-to-block variance, and residual variance were removed from the time series [10].
The analysis of variance components in the G-study (see Table 3) showed that for one assessor and one portfolio task, the variance due to factors related to the student was 11%.
The posterior expectations of the task-specific variances ranged from 1.00 to 1.35, while the posterior expectations of the group factors' variances ranged from 0.012 to 0.045.
Without auditory stimulation and a specific task, the variance in rCBF might increase, resulting in less statistical power when comparing conditions to the baseline.
Alone among these ROIs, the more superior visual region responded additionally to the task-irrelevant variance UVi (Fig. 2 d), whereas the more ventral visual region responding to variance also responded to UMr [ t(20) = 1.80, P < 0.04] (Fig. 2 e).
In our study, we only focused on the predetermined region (region of interest, ROI) of thresholded voxels with task-related variance in the ventral temporal cortex, as opposed to the whole-brain space (around 20,000 40,000 voxels).
In both models, in addition to regressors of interest, realignment (movement) regressors, regressors indicating volumes where "bad scans" had been replaced by interpolation of neighboring volumes, and mean time-series extracted from white matter and outside of brain masks were included to reduce task-unrelated variance (noise).
