Neuronal activity was recorded extracellularly from the left motor cortex using either platinum tungsten quartz insulated microelectrodes Volasertib pulled toafinetipandmechanically sharpened, or commercially available tungsten varnish insulated electrodes. The impedance of the electrodes was 2 4M. After the electrode reached the depth of the cortex where clear responses of many neurons to limb movements could be observed, two 200 m platinum iridium wires were slowly inserted and lowered into the medullar pyramid through the guide tubes implanted during surgery. Pulses of graded intensity were delivered through this bipolar electrode. The wires were fixed at the position which was most effective in eliciting antidromic responses in neurons of the motor cortex, and served as the pyramidal tract stimulating electrode during subsequent experiments.
The criterion for identification of antidromic responses was the test for collision of spikes. Signals from the microelectrode preamplifier, as well as fromthe platformposition and body position sensorswere amplified, digitized with a sampling frequency of 30 kHz,and SB-715992 400 Hz, displayed on the screen, and recorded to the disc of a computer by means of data acquisition software. Before, during and after testing in each postural task, all encountered neurons were tested for antidromic activation. In addition, the waveform analysis was employed to discriminate and identify the spikes of a single neuron using the Power 1401/Spike 2 system waveform matching algorithm. Only the neurons with a stable response latency and spike shape, which consistently satisfied the collision test, were used for the analysis.
The somatic receptive fields were examined in resting animals under conditions of head restraint. Stimulation was produced by palpation of muscle bellies, tendons, etc, and by passive movements of joints. The size of receptive fields was determined by listening to the audio monitor, and measuring the entire area, fromwhich action potentials could be elicited. A directional selectivity was assessed by comparing the number of spikes elicited by stimulation in the optimal direction and the direction opposite from optimal. Postural tests The basic experimental arrangement for postural tests was the same as in our previous study. The unrestrained cats were trained to quietly stand on a platform, which consisted of two parts the F platform under the forelimbs and the H platform under the hindlimbs.
They were rewarded by a paste food continuously ejected from the feeder. The feeder was positioned in front of the cat at a height of 21 23 cm. The platforms under the cat were periodically tilted in the frontal plane of the animal. A sine like tilt trajectory was used, with a period of 1 s and amplitude of 15 deg. The cats were easily engaged in this postural task and maintained equilibrium during tilts. They tended to compensate for the platform tilts by performing lateral displacements of the body in relation to the supporting platform, which allowed them to hold the mouth against the feeder and keep licking food despite the platform tilts. Postural tests differed in the composition of the group of limbs, which supported the body. This composition is reflected in the name of each test. A contribution of afferentat