E. Altenmuller et al., MODULATION OF SURAL NERVE SOMATOSENSORY-EVOKED POTENTIALS DURING STANCE AND DIFFERENT PHASES OF THE STEP-CYCLE, Electroencephalography and clinical neurophysiology. Evoked potentials, 96(6), 1995, pp. 516-525
In order to investigate the modulation of somatosensory processing dur
ing stance and locomotion, sural nerve somatosensory evoked potentials
were recorded during both stance and different phases of the step-cyc
le. Characteristic sequences of negative-positive waves were elicited,
consisting of an early component, N40, presumably of subcortical orig
in, followed by a P50-N80-P220 complex of cortical origin. The N40 and
N40-P50 components had similar amplitudes in both gait and stance. Ho
wever, the P50-N80 component was attenuated whereas the N80-P220 compl
ex became biphasic during gait. Within the step-cycle, amplitudes of t
he cortical components P50-N80 and N80-P110 were larger prior to footf
all and smaller at the beginning of the support phase. The results dem
onstrate that locomotion produces a modulatory effect on somatosensory
input at a cortical level. Within the step-cycle, excitability of the
somatosensory cortex is increased during the middle and late swing ph
ases and decreased during the support phase. Such modulation may contr
ibute to an improved detection of foot contact at touchdown.