There were no other significant interactions among groups, target, context or medication or high-order interactions among these factors for spatial or verbal trials.
The examination of the responses given by the subjects after having been asked about their coding strategies revealed that the overwhelming majority of them used verbal coding for all verbal trials (92% of subjects) and refrained from doing so in the non-verbal trials (75% claimed to have used verbal coding at no time or only seldom).
That is, when we searched for stimulus-type-specific effects (e.g., verbal vs. grating), the first condition referred to the mean power in all verbal trials, the second condition referred to the mean power in all grating trials, and both conditions were calculated from the same time interval (e.g., encoding).
The different results for verbal versus non-verbal trials may therefore be regarded as a consequence of the participants' coding strategies.
The few subjects who had attempted to use verbal coding for non-verbal trials reported to have used the words "tilted"/ more tilted".
We believe that, although accuracies differed between verbal and non-verbal trials, the results may be interpreted as a result subjects' coding strategies and not to differing stimulus properties, a major problem in previous WM studies.
The behavioral results showed slower responses for both spatial and verbal monitoring trials compared to non-monitoring trials.
The largest effect sizes were observed for the number sequencing and number-letter switching conditions of the Trail making test, time first move and time per move in the Tower test, semantic and set-shifting trials of the Verbal fluency test and set-shifting trial of the Design fluency test.
Again, we found no substantial differences between saccades and verbal response trials (not shown).
We found no significant differences between the saccade and the verbal response trials (p>0.15 for every F-test containing the response modality as factor), suggesting that the mode of response is irrelevant in this kind of perceptual decision.
