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Surgery and Histology
Animals were prepared for surgery with intraperitoneal injection of Nembutal (50 mg/kg). Lesions were placed stereotaxically through an electrode with a 1 mm uninsulated tip, by passage of 20 mA of radio frequency current for 20 sec. Sham lesion controls were prepared by an identical procedure, including lowering of the electrode into the brain, but no current was passed. The stereotaxic atlas of Konig and Klippel  was used to determine the coordinates of the desired lesions. Bilateral lesions were aimed at the ventrobasal thalamus in 11 rats, while unilateral lesions were aimed at the same region in 4 rats. Three animals received bilateral sham lesions. One received bilateral lesions directed at the parafascicular nucleus and one at the medial lemniscus posterior to the point where it enters the thalamus .
Histological assessment of the lesions was made following Nembutal anesthesia and perfusion with 0.9% saline followed by 10% Formalin. The head was removed and soaked in 10% Formalin for one or two days. The brain was blocked into the stereotaxic plane on a stereotaxic instrument and 50 μm sections were taken every 250 μm of sectioning. The sections were stained with cresyl violet and mounted permanently. Lesions and gliosis were drawn onto atlas sections from Pellegrino and Cushman .
Sensory Deprivation Procedures
The sequence of sensory deprivation procedures and the recovery time from anesthesia are shown in Table 1. Animals with bilateral and sham lesions received facial anesthesia. Animals with unilateral lesions received a combination of facial anesthesia and closure of one or the other eye.
Animals were prepared for facial anesthesia by application of the short acting general anesthesia, halothane. A local anesthetic, 2% lidocaine, was then injected at 9 points on the animal's face and head; one under each ear, one into each vibrissal pad, one on each cheek below the eye, one on the top of the head, one on the top of the nose, and one on the lower jaw. The vibrissal pads received 0.2 ml of lidocaine solution and the other points received 0.1 ml each. No testing was done until 30 min after halothane administration.
Suturing of the eyes and removal of sutures was also done under halothane anesthesia. Animals in which the eyes were sutured were allowed one day of recovery from the stress of suture application before they were tested.