Previous research has suggested that the stimulus-preceding
negativity (SPN) is largely independent of stimulus modality.
In contrast, the scalp topography of the event-related
desynchronization (ERD) related to the anticipation of stimuli
providing knowledge of results (KR) is modality dependent. These
findings, combined with functional SPN research, lead to the
hypothesis that anticipatory ERD reflects anticipatory attention,
whereas the SPN mainly depends on the affective-motivational
properties of the anticipated stimulus. To further investigate
the prestimulus ERD, and compare this measure with the SPN,
12 participants performed a time-estimation task, and were informed
about the quality of their time estimation by an auditory or
a visual stimulus providing KR. The KR stimuli could be either
intact or degraded.
Auditory degraded KR stimuli were less effective than other
KR stimuli in guiding subsequent behavior, and were preceded
by a larger SPN. There were no effects of degradation on the
SPN in the visual modality. Preceding auditory KR stimuli no
ERD was present, whereas preceding visual stimuli an occipital
ERD was found. However, contrary to expectation, the latter
was larger preceding intact than preceding degraded stimuli.
It is concluded that the data largely agree with an interpretation
of the pre-KR SPN as a reflection of the anticipation of the
affective-motivational value of KR stimuli, and of the prestimulus
ERD as a perceptual anticipatory attention process.