retinal stimulus patterns would result in identical cortical activity patterns: fan shapes, concentric circles, and spirals imaged on retinaall map to cortex as parallel stripes of cortical activity. Some corol-laries of this are the following: (a) If parallel stripes of cortical activityform spontaneously, their percept is governed by orientation of thestripes on cortex (Ermentrout & Cowan, 1979). (b) Perceptuallyopponent shapes, like fan shapes and concentric circles, are associatedwith orthogonal patterns of cortical activity (as are clockwise andcounterclockwise spirals). (c) Scrolling stripe patterns on cortex leadsto rotating fan shapes and spirals and to expanding/contracting con-centric circles. (d) Rotating stripes of cortical activity morphs per-cepts—fan shapes twist into spirals, which progressively tighten until becoming concentric circles; multistability between hallucinatory pat-terns could result. Much hallucinatory diversity can thus be explainedby the interaction of cortical stripe formation with the nonlinearretinocortical mapping. Received May 13, 2011 Revision received October 12, 2011 Accepted November 16, 2011 /H18546774 BILLOCK AND TSOU