A craniotomy in stereotaxic coordinates was positioned according to the visuotopic map of area 19 (Tusa et al., 1979). A plastic cylinder around it was glued with dental acrylic forming a well. Then a small opening was made in the dura mater where stainless steel microelectrodes (impedance 7–12 MΩ; FHC, Bowdoinham, ME, USA) were positioned vertically above the recording site. The well was filled with 4% agar in physiological saline then sealed with warm liquid wax (melting point ~40°C). Using a hydraulic micromanipulator (David Kopf’s Instruments Tujunga, CA, USA) the electrode was advanced slowly (20–60 μm/min) along the medial suprasylvian sulcus (MS in Figure 1A).