Neurophysiological evaluation
depression
SKIN, RECRUITMENT
Subject remained seated on a gurney with hips and knees flexed at 90°, with back support. A footstool (adaptable in height) was on the floor to give feet support. Self‐adhesive electrodes were used for recording and applying stimulation.After skin preparation, the soleus EMG was acquired by means of surface electrodes arranged in a belly–tendon manner, with the reference electrode on the Aquilles tendon and the active electrode on the soleus muscle; the ground electrode was placed ≈4 cm above the active electrode. EMG signals were recorded by means of D360 amplifiers (Digitimer), amplified (×250–1000) and bandwidth filtered between 3 and 3000 Hz. EMG was sampled at 10 kHz and stored in a computer by means of a CED 1401 mkII Power A–D converter (Cambridge Electronic Design), which also triggered a Digitimer DS7A stimulator. Skin temperature was monitored (only in one group, reasons given below) by means of a fine temperature probe attached just at the side of the active EMG recording electrode, the probe was connected to a Cibertec Citer which sampled temperature at 0.1 Hz and delivered the signal to the CED1401; therefore, temperature recording was synchronized to EMG recording.We stimulated the tibial nerve (1 ms pulses) with the cathode on the popliteal fossa and the anode over the patella. Stimulation pulses were delivered at 0.1 Hz to avoid any induction of post‐activation depression. Different stimulation intensities were used to record the H‐reflex (at two points of the ascending‐leg of the recruitment curve) and the compound muscle action potentials (CMAP). Ten responses were obtained for each intensity.For each time‐point (pre, post, post‐2), peak to peak amplitude and latency of the following variables were studied (in this order):
CMAP acquired at stimulation intensity 20% above the supramaximal.HHSkin temperature (only recorded in one group) was analyzed in Celsius grades; skin temperature is a valid parameter to estimate muscle temperature as shown previously (de Ruiter et al., 