Figure 6.

Absence of orientation maps. To exclude the possibility that orientation preference columns were indeed present but too weak to be revealed by single conditions (i.e., blank normalized maps), differential maps were also computed in which responses to orthogonal orientations were subtracted from another (third row from left). Depicted are the first frames in which significant activity was recorded (VSD imaging) and a time-averaged map (intrinsic optical imaging; right). A corresponding frame depicting the response to a blank condition was included for both these techniques. Scale bars, 1 mm.