Event-related potentials to conjunctions of spatial frequency and orientation as a function of stimulus parameters and response requirements

Event-related potentials (ERPs) were recorded from 7 male graduate students who were required to push a button in response to a given conjunction of spatial frequency and orientation (target) and to ignore conjunctions sharing with the target only frequency (frequency-relevant), only orientation (orientation-relevant), or neither (irrelevant). Data do not provide direct evidence for the neural-specificity theory stating that task-related selective ERP responses reflect differential enhancement of activity in stimulus-specific pathways. It is concluded that ERPs associated with selection of frequency and orientation are highly comparable to those associated with other visual dimensions (e.g., color) and that selection of multiple visual dimensions may be hierarchical at one level of processing and independent at another.