Animal preparation and recording procedures followed the guidelines of the Australian Code of Practice for the Care and Use of Animals for Scientific Purposes and were approved by the Animal Care Ethics Committee of The University of Sydney. The effects of PTV cooling on background activity and responses of area 19 cells were tested in four adult female cats (Felis catus) weighing 2.5–3.4 kg. Animals were initially anesthetized with a gaseous mixture of 2.5%–5% of halothane in N2O/O2 (67%/33%). Throughout subsequent surgery, halothane level in the mixture was reduced to 1%–2%, while throughout the single-neuron recording sessions and between the intervals, halothane level was kept within 0.4%–0.8%. A tracheotomy was performed in order to reliably maintain artificial ventilation. Right cephalic vein was cannulated to allow continuous slow infusion of nutrients and paralyzing agent gallamine triethiodide injected at a rate of 10 mg/kg/h. Gallamine triethiodide-block resistant, residual eye movements were largely eliminated by bilateral cervical sympathectomy (see Rodieck et al., 1967). Opportunistic infections, brain swelling and excessive mucous secretion were controlled by daily injections of respectively the antibiotic amoxycillin trihydrate (75 mg, i.m.), dexamethasone phosphate (4 mg, i.m.) and atropine sulfate (0.3 mg, i.m.). Body temperature (37.5°C), heart rate (180–220 beats/min), alveolar CO2 level (3.5%–4%) and electroencephalogram (δ waves 0.5–4 Hz) were continuously monitored and maintained at appropriate levels. Phenylephrine hydrochloride (0.1%) was applied to each eye to block accommodation and to retract nictitating membranes. Pupils were dilated by daily applications of a couple of drops of atropine sulfate (1%). Neutral-power, air-permeable plastic contact lenses (radius 8.5 mm) were fitted to protect the corneas from drying. Artificial pupils (3 mm in diameter) and corrective lenses were placed in front of the eyes. Refractive power of corrective lenses necessary to focus the eyes on a tangent screen located 57 cm in front of the cat was determined by slit/streak retinoscopy (range: +0.5 to +3.0 diopters). In order to monitor the residual eye movements, positions of optic discs and areae centrales (Bishop et al., 1962) were, back-projected, at least twice daily, onto the tangent screen using a fiber-optic light source (Pettigrew et al., 1979).