Biomedical Engineering Reference
In-Depth Information
Figure 5
. Postural responses from the tibial anterior muscle elicited by a tilting platform (US)
obtained from two control subjects exhibiting strategy I and II, and a cerebellar patient without
presenting one of these strategies. Stack plots with the first (1) trial on the top and the last trial
at the bottom of each stack plot. Stack plots are constructed from 70 US-alone trials, 80 CS-US
trials, and 20 US-alone trials. Analysis time is 1400 ms. The conditioning stimulus (CS) and
unconditioned stimulus (US) are marked by cursors. The movement function with its character-
istic parameters, representing the US, the onset and duration of CS, marked by a shaded bar,
are below the stack plots. Note that during paired trials the subject using strategy I established
CR whereas the subject using strategy II did not but exhibited remarkable decay of the UR.
The cerebellar patient did not profit from the occurrence of the CS.
in the motor task studied. On the other hand, in cerebellar patients we did not
find a CVP-based CR, which thus coincided with a lack of the corresponding
muscle activity. During conditioning controls reduced their deviations in both
directions, whereas that of the patients remained unchanged.
In the initial
US-alone
trials the decay of UR amplitudes is most likely due
to a habituation process. The mean UR amplitude at the end of the US-alone
trials was 79.1 10.9% for the controls and 84.4 5.9% for the patients with
respect to the mean amplitude (set to 100%) of the first 10 trials at the beginning
of the session. Although the mean values just missed significance, there was a
clear tendency to a smaller decay in cerebellar patients. During paired trials the
UR attenuations were larger in both groups, but the final difference was signifi-
