Figure 3.

Neural responses in nearby barrel and septum columns. Electrode 1 (star 1) was positioned in the column of the septum between barrels B3, B4, C3, and C4. Electrode 2 (star 2) was positioned in the column of barrel C4 (a). Deflection of whisker C4 increased neural activity in both locations. The mean spike rate υ of the five cells in the barrel column (triangles, logarithmic ordinate) increased with increasing stimulus frequency f up to 9 apps (b), beyond which it approximately halved, resulting in the greatest disparity with the logarithmic trend line (dashed line, equation). The mean response efficacy ρ (squares, linear ordinate) peaked at 1 apps and then declined to the lowest level observed in the present study at 18 apps. In contrast, the mean υ of the six septum column neurons increased in good correspondence with logarithmic growth (c; same conventions as in b). Their response efficacy peaked at 1 apps, decreased less rapidly with increasing f than in the barrel columns, and approached a steady state at frequencies ≥6 apps. The bars through the means represent ±1 SD.