170mm x 244mm Collerton c10. tex V3-11/21/2014 5:28 P. M. Page 245 10. 4 EXTENSIONS OF THE MODEL 245 Figure 10. 24 The development of a scintillating scotoma experienced while reading a book. Thesequencestartswiththeupper-leftpanelandproceedsclockwise. Theentireepisodelastsfor about 20-30min. Source: Reproduced withpermissionof J& A Churchill. Figure 10. 24 shows the development of a scintillating scotoma while the subject was reading a book. From this and similar sequences of images, it was possible to estimatethepropagationvelocityin V1asabout2-3mm/min. Myowncalculations onsimilardatakindlysenttomeby G. Baumgartnerand B. Hassenstein,someyears ago,provideanestimateof1. 5mm/min. Toobtainsuchestimatesisstraightforward, one simply maps the imagery, which is in retinal or visual field coordinates (r,𝜃) into V1 coordinates (x,y)using equation 10. 3, the retino-cortical map. It turns out that the forms obtained from such a transformation are propagating circular wave patterns (Grüsser, 1995). Therehavebeenanumberofattemptstomodelthespreadofsuchpatterns,essen-tiallybypropagatingatravellingwaveofspreadingdepressionoveramodelof V1, basedlargelyonanearlypaperby Tuckwelland Miura(1978). Severalpapersalong theselineshavesubsequentlybeenpublished,forexample,Reggiaand Montgomery (1996) and Dahlem and Müller (2004). The paper by Reggia and Montgomery (1996) tries to take into account V1 circuitry but lacks any representation of orien-tation preference and therefore fails to generate the appropriate local patterns seen by observers. It remains to develop a model including orientation preference in V1 circuitry that iscapable of generating the patterns shown in Figures 10. 24. 10. 4. 6 Complex hallucinatory images There are many more complex visual images that do not fit easily into the theoretical framework we have presented here. Figure 10. 25 shows two examples. Figure10. 25ashowsanimagegeneratedbybinocularpressureontheeyeballs,and