Fig. 3.

Layer 2/3 neurons exhibit prominent length summation, whereas layer 4 neurons do not. The top rowshows two examples for each response type; blackindicates a single unit record, and gray indicates a multiunit record. The bottom row shows population average (error bars ± 1 SD), with arrowsindicating the extent of average MDF for each layer, gray lines showing exponential fits, and dashed linesindicating 90% of asymptote. A, Length summation in layer 2/3 neurons. B, Length suppression found in 14 of 33 recording sites in layer 4. C, Lack of prominent summation or suppression in 19 of 33 sites in layer 4.