These are labelled as the early bin (160 200 ms, post item onset), the mid-latency bin (320 480 ms) and the late-latency bin (480 800 ms).
Only the duration between item onset and response (i.e. not the entire 9 seconds) was modeled for the fMRI analysis.
The first effect consisted of a bipolar modulation over frontal and occipital scalp sites shortly after item onset.
EEG epochs extending from 100 ms before item onset until 924 ms thereafter were extracted from the continuous record.
Importantly, the late effect is not simply a continuation of that seen shortly after item onset; the scalp distributions of the two effects differed.
However, switch trials can also give rise to modulations over frontal scalp sites, which can be negative- or positive-going relative to stay trials following item onset (Jackson et al., 2001; Rushworth et al., 2002; Swainson et al., 2003).
Following item onset, switch trials have been shown to elicit positive-going modulations over posterior scalp sites at different times (Jackson et al., 2001; Karayanidis et al., 2003; Mueller et al., 2007; Rushworth et al., 2005; Swainson et al., 2003, 2006).
The CAM or CAM-ICU is a highly sensitive and specific method that evaluates subjects for the presence of four items: acute onset of cognitive changes fluctuating in course, inattention, disorganized thinking, and altered level of consciousness.
Previous research showed that when a probe item is different from the memorized item in a one-item change detection task, a negative component will be elicited at around 270 ms (N270) after the probe item's onset, predominantly exhibiting a frontal distribution [33], [55], [56] with the source at anterior cingulate cortex (ACC) [57].
Instead, the probability of a test taker providing a correct response to items after PD onset is independent of proficiency; rather, it corresponds to an item-specific response threshold.
