WITHIN THE SOMATOSENSORY SYSTEM: THE ROLE OF CUTANEOUS AND PROPRIOCEPTIVE INPUTS IN TEMPORAL DISCRIMINATION OF MOVEMENT
Poster Presentation

Mirta Fiorio
Dipartimento di Scienze Neurologiche e della Visione, Università di Verona

Clementina Stanzani

Giuseppe Moretto

Antonio Fiaschi

Michele Tinazzi

     Abstract ID Number: 102
     Full text: Not available
     Last modified: March 21, 2005

Abstract
Timing is an important part of complex somatosensory functions. Normal temporal discrimination of cutaneous stimuli ranges from 30 to 40 ms. Timing information is also of importance to the CNS if it is to use proprioceptive inputs to provide information on position and movements of one body part with respect to another. Yet despite this, we know of no psychophysical studies on temporal discrimination of movement. We tried to address this question by stimulating the motor point of the first dorsal interosseous muscle (FDI) with different time intervals. This produced contractions of the muscle and movement of the index finger. The shortest inter-stimulus interval at which subjects reported the perception of two separate movements (temporal discrimination movement threshold, TDMT) was 75 ms. In order to assess the role of muscle and cutaneous afferents in TDMT, we also stimulated the radial nerve, which supplies the cutaneous territory overlying the muscle, and the ulnar nerve, which supplies muscle afferents. Stimulation of ulnar nerve increased TDMT by 40 ms. Stimulation of the radial nerve increased TDMT only by 16 ms, suggesting that this task may preferentially employ perception of input in muscle afferent fibres, although with a smaller contribution from other sources such as skin and joints.