Abstract
The somatosensory temporal discrimination threshold (STDT) is the shortest interval at which an individual recognizes paired stimuli as separate in time. We investigated whether and how voluntary movement modulates STDT in healthy subjects. In 17 healthy participants, we tested STDT during voluntary index‐finger abductions at several time‐points after movement onset and during motor preparation. We then tested whether voluntary movement‐induced STDT changes were specific for the body segment moved, depended on movement kinematics, on the type of movement or on the intensity for delivering paired electrical stimuli for STDT. To understand the mechanisms underlying STDT modulation, we also tested STDT during motor imagery and after delivering repetitive transcranial magnetic stimulation to elicit excitability changes in the primary somatosensory cortex (S1). When tested on the moving hand at movement onset and up to 200 msec thereafter, STDT values increased from baseline, but during motor preparation remained unchanged. STDT values changed significantly during fast and slow index‐finger movements and also, though less, during passive index‐finger abductions, whereas during tonic index‐finger abductions they remained unchanged. STDT also remained unchanged when tested in body parts other than those engaged in movement and during imagined movement. Nor did testing STDT at increased intensity influence movement‐induced STDT changes. The cTBS‐induced S1 cortical changes left movement‐induced STDT changes unaffected. Our findings suggest that movement execution in healthy subjects may alter STDT processing.
Highlights
Ample evidence describes changes in brain processing of tactile sensory information while healthy subjects prepare and execute voluntary movements (Brown et al 2013)
When tested on the moving hand at movement onset and up to 200 msec thereafter, somatosensory temporal discrimination threshold (STDT) values increased from baseline, but during motor preparation remained unchanged
In healthy subjects we provide new evidence showing that movement execution brings about changes in the temporal processing of tactile information – as tested with STDT
Summary
Ample evidence describes changes in brain processing of tactile sensory information while healthy subjects prepare and execute voluntary movements (Brown et al 2013). Whether and how voluntary movement modulates the STDT in healthy subjects is unknown Having this information might help in designing studies to clarify the pathophysiological mechanisms underlying the altered STDT values reported in patients with movement disorders (Artieda et al 1992; Bradley et al 2009; Scontrini et al 2009; Conte et al 2010, 2014; Lee et al 2010; Tinazzi et al 2013; Kimmich et al 2014). To understand the mechanisms underlying movement-induced STDT changes, we tested STDT during motor imagery and after delivering repetitive transcranial magnetic stimulation to elicit excitability changes in the primary somatosensory cortex (S1)
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