Figure 8.
Lowered HCN makes the thalamic alpha more sensitive to small changes in the calcium conductance. A, Colored lines show deviations from normal HCN expression levels. Systematically varying the calcium conductance in both directions leads to sudden increases in the entropy describing incoherent firing of the HTC cells. Lower HCN expression (gH = 0.28 and 0.32 mS/cm2, maroon and red) have a lower tolerance for changes in calcium. This is seen as narrower windows of low entropy compared with the normal expression of HCN (gH = 0.36 mS/cm2 black). Inset shows time series of the LFP when calcium conductance is enhanced by ∼18% for reduced HCN expression (maroon, gH = 0.28 mS/cm2, irregular firing) and normal HCN expression (black, gH = 0.36 mS/cm2, regular 10-Hz firing). Horizontal line (dashed dark blue) marks the threshold (5.0) for entropy beyond which we see irregular firing. B, Tolerance to changes in calcium conductance decreases with decrease in HCN expression. For calcium conductance above the threshold value associated with each gH, irregular firing is seen.