The experimental fMRI-design was mixed; blocks of stimuli were presented in a rapid event-related design.
Individuals will be randomised per centre in each of the four participating centres in mixed blocks of four and six to prevent unequal randomisation within the centres [ 26].
However, older adults performed similarly to younger on neutral category words and neutral words in mixed blocks of our study, suggesting that memory deficits on neutral blocks was not an issue.
We observed an age-related diminishment in carry-over slowing effects for the mixed blocks of an emotional Stroop task, consistent with other findings of a decrease in the "negativity bias" with age.
McNally, Amir & Lipke (1996) [ 29] compared RTs by Vietnam combat veterans with and without PTSD over 4 mixed blocks of words (96 words each), in response to 4 word types: trauma, positive, neutral and color words.
We used functional magnetic resonance imaging (fMRI) to investigate differences in the functional anatomy of the TS brain while participants performed mixed blocks of the manual task-switching paradigm outlined in experiment 1.
Distractor costs are large in mixed blocks of the task, when the visual features used to define the target on any one trial can be used to define a distractor in subsequent trials (Hickey et al., 2006; Theeuwes, 1991).
Additionally, a few neutral buffer words (2 4 words) were placed at the start of each mixed block to help ensure that subjects were unaware of the repeating pattern.
One investigator (MJS, who administered the intervention) used an interactive voice response telephone service provided by the National Health and Medical Research Council Clinical Trials Centre at the University of Sydney to carry out permuted block randomisation with mixed block lengths of four and six participants.
Permuted block randomisation with mixed block lengths of four and six participants was undertaken by the investigator (MJS, the person administering the intervention) using an interactive voice response telephone service provided by the National Health and Medical Research Council Clinical Trials Centre at the University of Sydney, Sydney, Australia.
