Fig. 2.
Visually evoked suppression is accompanied by an increase in the membrane conductance. A, Reconstruction of the cell, a spiny stellate cell in layer 4. B, A dark square flashed within the on subregion evoked a brisk hyperpolarization, as shown in three individual trials of the stimulus and the average of sixteen trials (bold).C, Top trace, Plot of conductance during the visual response: g(t)=K(Ip −In)/(Vp(t) − Vn(t));g(t) is the normalized conductance at time t, Ip −In is the difference between the values of constant current injected through the electrode, andVp(t) andVn(t) are the membrane voltages recorded while the membrane was held at the relatively positive and negative levels. The averaged responses obtained at the control and hyperpolarized levels that were used to calculateg(t) are shownbelow the graph. Grid spacing was 0.85°.