Reanalysis of "Bedside detection of awareness in the vegetative state: a cohort study".

Submissions should be made via our electronic submission system at http://ees.elsevier.com/ thelancet/ details), there is no statistical evidence of a task-related signal. To take into account correlations between blocks, we defined accuracy using all block-pairs as test components, 6 rather than restricting consideration to adjacent block pairs. To account for dependence among trials, we determined significance via a permutation test that recognised the block design. With this approach, significance remained in positive controls, but in only one patient (P13) (p=0·0286; lowest possible p-value with four blocks). We further note that even for random data, a classifier would be expected to yield one in 20 positive individuals at p≤0·05. We therefore corrected for multiple com parisons via the false-discovery rate (FDR); 7 significance at p≤0·05 remained for controls but for none of the patients. Finally, we applied an independent approach that asked whether there was a significant difference between task and rest periods, by use of univariate statistics (ie, separate tests for each frequency and channel of the EEG; 8 appendix, webfigures 3 and 4). Controls showed the expected task-related changes in motor imagery tasks (decreases in EEG power from 7 to 30 Hz, especially over the motor cortices contralateral to the imagined limb movement; p≤0·05 after FDR correction). None of the 16 patients had significant changes identified by this measure. This finding emphasises that, even if we were to accept Cruse and colleagues' " positive " patient classifications as different from chance, the EEG signals lack the expected physiological changes associated with motor imagery (by contrast with the suggestion made by Cruse and colleagues in connection with their figure 2). In sum, we found that Cruse and colleagues' method is not valid because the patient data do not meet the assumptions of their statistical model. Specifically, the model does not allow for correlations between nearby trials and blocks, which are likely to be induced by fluctuating Reanalysis of " Bedside detection of awareness in the vegetative state: a cohort study " In 2011, Damian Cruse and colleagues 1 reported that a new EEG-based tool was able to show that three of 16 patients in a vegetative state performed a motor imagery task requiring language and short-term memory. This finding, if confirmed, has major implications for diagnosis and care of severely brain-injured patients. We were concerned about the method's validity because of the difficulty of the task, and its critical reliance …