Dissociated effects of quiet stance on standard and high-frequency (600 Hz) lower limb somatosensory evoked potentials.
OBJECTIVE
To verify whether standing can modulate somatosensory input from lower limb to the cortex. Somatosensory afferents have been evaluated not only by means of somatosensory evoked potentials recorded by means of classical wide-bandpass filtering (standard SEPs), but also by high-frequency somatosensory evoked potentials (HF-SEPs), which probably play a role in the processing of rapid adaptive changes.


METHODS
Eight healthy subjects underwent right posterior tibial nerve (PTN) stimulation in two different conditions (standing and lying supine). Standard SEPs reflecting the activity of both subcortical and cortical generators further underwent digital filtering (300-800 Hz), in order to enhance HF-SEP components.


RESULTS
Stance significantly reduces the P40 cortical component of standard SEPs. By contrast, HF-SEPs did not show any significant change between the two conditions.


CONCLUSIONS
The lack of any gating effect on HF-SEPs lends further substance to the hypothesis that HF-SEPs play a pivotal role in the processing of somatosensory inputs related to rapid adaptive changes.


CONCLUSIONS
Our data confirm that standard and HF-SEPs reflect two distinct mechanisms with strongly different functional significance. Further studies are needed to definitively establish whether this dissociation is merely caused by the activation of anatomically different neuronal pools, or by the involvement of distinct functional mechanisms.
Restuccia
Domenico
D
IRCCS "La Nostra Famiglia - E. Medea", Polo Friuli Venezia Giulia, Via cialdini 29, 33037 Pasian di Prato, Udine, Italy. restuccia@pp.lnf.it
Micoli
Barbara
B
Cazzagon
Monica
M
Fantinel
Rachele
R
Piero
Ivana Del
ID
Della Marca
Giacomo
G
D000328:Adult; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation / Q000379:methods; D005073:Evoked Potentials, Somatosensory / Q000502:physiology* / Q000528:radiation effects; D005260:Female; D006801:Humans; D035002:Lower Extremity / Q000294:innervation*; D008297:Male; D008875:Middle Aged; D011187:Posture; D013003:Somatosensory Cortex / Q000502:physiology / Q000528:radiation effects*; D013057:Spectrum Analysis; D013979:Tibial Nerve / Q000502:physiology / Q000528:radiation effects; D013997:Time Factors