Systematic errors for saccades to remembered targets: evidence for a dissociation between saccade metrics and activity in the superior colliculus.

Pronounced systematic errors are a consistent feature of saccades to remembered target locations. In an effort to determine their neural basis, we recorded from saccade-related burst neurons (SRBNs) in the superior colliculus and compared the discharges associated with saccades to visual and remembered targets. For all recorded SRBNs, the relationship between discharge rate and saccade metrics differed for saccades to visual and remembered targets; movement fields constructed from saccades to remembered targets were shifted relative to those for visual targets. The shifts of the remembered movement fields were consistent with the direction and magnitude of the systematic errors observed on memory trials. These findings suggest that the superior colliculus is not the source of the systematic errors observed on memory trials. Systematic errors are likely due to the addition or omission of signals downstream from the superior colliculus.