At 10 points around the circumference of the head, stainless steel screws were screwed BI6727 into the skull and connected together with a wire, the screw heads and the wire were then inserted into a plastic cast to form a circular base. Later,while searching for neurons before behavioural tests, awake cats were rigidly held by this base. The base was also used for fixation of connectors, a miniature micro drive, preamplifiers, contacts for stimulating electrodes, and a protective and electrically shielding cap. A portion of the skull and dura above the left motor cortex, over approximately 0. 6 cm2, were removed. The area of the motor cortex was visually identified by the surface features and photographed. The aperture was then covered by a plastic plate 1mm thick, in which approximately 100 holes had been drilled and filled by sterile wax.
The plate was fastened to the surrounding bone by orthodontic resin. Two 26 gauge hypodermic guide tubes were implanted vertically above the medullar pyramid at the Horsley and Clarke coordinates and, at the Origin of cortical responses in postural tasks 249 depth of H 0 for insertion of stimulating electrodes into Ispinesib the pyramidal tract later in the awake state. Following the surgery, the cat was placed in a warm padded cage and respiration and reflexes were monitored until it regained conscious. Analgesic enrofloxacin was administered intramuscularly on the day of surgery and two times a day for five to seven subsequent days. Triple antibiotic ointment bacitracin neomycin polymyxin was applied daily to wounds margins around the head implant for the duration of experiments.
Identification of cortical motor area After several days of recovery, experiments were initiated by placing the animal in the head restraining device. The cat was positioned on a table equipped with a foam rubber pad, encouraged to take a,sphinx, position, and allowed to rest for several minutes. Then the base attached to the skull during surgery was fastened to the restraining device so that the resting position of the cat,s head was approximated. This procedure minimized stress on the neck while the head was temporarily immobilized and the body was put in a comfortable position. Over several days, a number of sessions of increasing duration were used to accustom the cat to the head restrainer. After several training sessions, all cats sat quietly with their head restrained.
They did not seem to be disturbed by the restrainer because they frequently fell asleep. Then neuronal recordings were initiated. A detailed description of the area of recording was given earlier. In brief, the area immediately adjacent to and inside the lateral half of the cruciate sulcus in the cat is considered to be the motor cortex. This is based on a considerable body of data obtained by means of inactivation, stimulation and recording techniques, as well as on histological considerations. The fine mapping of the body parts in the cortex varies in different subjects, however. In order to delineate the fore and hindlimb representations of the left motor cortex in each subject, three approaches have been used: somatic receptive fields mapping, observation of neuronal activity during voluntarymovements, and intracortical microstimulation. Cell recording and identi