The centers of the RFs (classical RFs − CRFs) of all 66 area, 19 cells studied were located within the contralateral visual hemifield in the region 0° − 32° from the vertical meridian and 2° − 15° from the horizontal meridian. The CRFs of all but two of 28 area 19 neurons examined for the effects of PTV inactivation were located within the part of the visual field represented in areas 20a and 20b (Figure 1C based on Tusa and Palmer, 1980). Our electrode penetrations proceeded along the middle suprasylvian sulcus and our sample is strongly biased toward particular cellular layers. Indeed, all but a couple of area 19 cells were recorded from the middle layers 3 and 4. Consistent with previous studies (see Tusa et al., 1979; Dreher et al., 1980; Duysens et al., 1982b; Rapaport et al., 1982; Dreher, 1986; Mulligan and Sherk, 1993), the RFs located more peripherally tended to be larger (Figure 1D). As indicated in Figure 1E, the majority of cells (85.5%; 66/77) were binocular and could be activated by appropriate stimuli presented via either eye (see Duysens et al., 1982a; Rapaport et al., 1982; Dreher, 1986; Pettigrew and Dreher, 1987; Tanaka et al., 1987; Guillemot et al., 1993; Tardif et al., 1997; Bergeron et al., 1998). About half of binocular cells (53%; 35/66) responded more strongly to stimuli presented via the contralateral eye (class 2 vs. class 4 cells—Figure 1E) with only a few cells (9/66; 13.5%) responding equally well to stimuli presented via either eye (class 3 cells). Note that the eye dominance distribution of area 19 cells tested for the effects of PTV inactivation was similar to that of the entire sample (Figure 1E).