Figure 6. Plots of the distribution of head orienting errors (target location minus final head bearing) for the different experimental groups before the insertion of the earplug (white) and on day 2 (pink and continuous line) and day 9 (green and dashed line) of wearing the earplug after bilateral implantation of drug-free Elvax over MEG (A) or muscimol-Elvax over the MEG (B), AEG (C) or PEG (D).

Quadratic polynomial curves were fitted using a robust least squares method (bisquare weights) to the data. Colour areas indicate the 95% confidence intervals in each case. Red crosses indicate trials on day 2 and green squares trials on day 9 of wearing an earplug. Trials before the insertion for the earplug have been omitted for clarity. Note that the confidence intervals for the preplug and day 9 earplug data almost entirely overlap in the control group (A), indicating near complete recovery in head orienting accuracy, whereas this is not the case for any of the groups with muscimol-Elvax (B–D).