MST neurons respond selectively to optic flow seen during observer self-movement. Spatial attention enhances MST neuronal responses to moving object stimuli (Treue and Maunsell, 1996) and spatial working memory alters both the magnitude and directional tuning of MST neuronal responses to optic flow (Dubin and Duffy, SFN 1999). We have now found that non-spatial working memory also affects these responses and that task difficulty robustly influences those effects. We recorded 190 MST neurons in two studies of responses to optic flow having foci-of-expansion (FOEs) at 30 deg eccentricity and 45 deg intervals around the centered fixation point. In the first study, two interleaved saccade tasks presented optic flow: a match-to-sample shape-memory task that included an optic flow distractor, and a flow-relevant task in which the FOE specified the location of the saccade target. Almost all (85%, 76/89) neurons were tuned for FOE location; 12% (9/76) showed significant task effects on the optic flow responses, mo...