, 1999 and Vogel et al., 2005). The CDA consists of a contra-minus ipsilateral negativity relative to the relevant INCB018424 nmr stimulus side. The CDA is maximal at posterior recording sites (PO7 and PO8) and is calculated by subtracting activity at ipsilateral electrode sites from the corresponding contralateral electrode sites. Most studies use bilateral stimuli in order to keep stimulation of both hemifields as comparable as possible. Thus, in agreement with Klaver et al. (1999) it may be argued that the CDA reflects the load on visual-working memory by spatial attention and can be used to examine if sequence
learning develops from an attentive to an automatic phase. In the present study, we examined whether differences between familiar and unfamiliar sequences are already
present while preparing these sequences. We predicted see more familiar motor sequences to be executed faster and with fewer errors than unfamiliar motor sequences. When comparing familiar and unfamiliar sequences in terms of general motor preparation, reflected in the CNV, several possibilities can be distinguished. First, behavioral differences in speed and accuracy may be solely due to processes active during the execution phase and not during preparation. Therefore no difference in general motor preparation between familiar and unfamiliar sequences may be predicted to be observed. Second, if the CNV reflects the complexity of the sequences (Cui et al., 2000) then there may be more general motor preparation before unfamiliar sequences as compared with familiar sequences, since unfamiliar sequences can be regarded as more complex than familiar sequences. This second option would predict a larger CNV during the preparation of unfamiliar sequences than for familiar sequences. Third, if the CNV reflects the amount of prepared keypresses or parameters (Schröter & Leuthold,
2009) then there may be more general motor preparation before familiar sequences as compared with familiar sequences, as more keypresses can be prepared for familiar sequences than for unfamiliar sequences. This would be reflected in a larger CNV during the preparation of familiar sequences compared with unfamiliar sequences. Regarding effector specific Cepharanthine preparation it may be argued that only the first keypress is prepared on an effector specific level (Schröter & Leuthold, 2009), which predicts no differences in LRP amplitude between familiar and unfamiliar sequences. The CDA is used to index visual-working memory. If more items are stored in visual-working memory during the preparation of unfamiliar sequences as compared with familiar sequences then the CDA may be enlarged for unfamiliar sequences. This could be related to the increased complexity of unfamiliar sequences, as with unfamiliar sequences individual items have to be kept in visual-working memory, whereas with familiar sequences segments of stimuli can be kept in visual-working memory.