Item

Abstract

It is well known, that sensory consequences of self-produced movements can be predicted and that this prediction can be used to attenuate the sensory effects. It has been shown that the
cerebellum is involved in predicting the sensory feedback of self produced movements and
thus it can modulate the somatosensory cortex activity [1].
In this study it is planned to investigate the performance of a tactile discrimination task during
rest and compare it to performance during active arm movement, respectively. Participants’
distal phalanx of the left index finger was glued to a metal pin of a custom developed Lateral-
Pin-Stroke-Device (LPSD) in order to provide pure skin stretch and to avoid cues derived from
pin slip parallel to the skin. The device is able to move the pin on a defined trajectory in any
radial lateral direction initiating from a central starting point. The task was to judge whether
the second of two pin strokes was shifted clockwise or counterclockwise compared to the first.
This experiment was performed under two different conditions—a static condition where no
arm movement was required and an active condition where participants had to perform an arm
movement in forward direction while they were doing the discrimination task.
Preliminary results show that direction discrimination performance is much higher in the
static condition. Participants were no longer able to reach the 84 discrimination threshold
in the active condition. These results are consistent with our expectations, i.e., a significantly
impaired tactile sensation during active movement. In analogy to saccadic suppression we will
discuss our results in terms of tactile suppression. Results indicate a slight anisotropy in terms
of a higher threshold in upwards- (towards the finger tip) compared to rightwards direction.
This seems to be in line with Keyson and Houtsma’s [2] findings.