Tactile stimulation during finger opposition does not contribute to 3D fMRI brain activity pattern.

Functional magnetic resonance imaging (fMRI) is a new, non-invasive technique to localize brain activity with a high spatial resolution. Activation of the motor cortex by sequential movement of the thumb to the fingers has been used extensively to validate the fMRI technique. This task, however, combines motor activity (movement of thumb and fingers) with tactile stimulation (touching the finger with the thumb). In this study we examined the contribution of tactile stimulation to the activity pattern. Nine healthy subjects were instructed to touch the fingers with the thumb in a first task, and repeat this movement without touching the fingers in a second task. Comparison of the two activity patterns did not result in a significant difference. Therefore we concluded that the pattern of activity associated with a fingertapping task is not influenced by tactile stimulation, but is caused primarily by motor activation and possibly by proprioceptive activity.