Brain Research, 211 (1980) 445-450 445 © Elsevier/North-Holland Biomedical Press Organization of direction preferences in cat visual cortex B. R. PAYNE, N. BERMAN and E. H. MURPHY Departments of Anatomy and Physiology~Biochemistry, The Medical College of Pennsylvania, Phila- delphia, Pa. 19129 (U.S.A.) (Accepted December 4th, 1980) Key words: cat -- visual cortex -- direction preference -- columnar organization Single unit recordings were made from the visual cortex of 5 adult cats. Visual stimuli were used to determine the stimulus orientation and direction of movement preferred by cortical cells. Analysis of the sequence of neurons recorded along each electrode penetration and their direction preferences indicates that neurons preferring similar directions of movement are clustered together in the cortex. Neurons in the visual cortex of cats and monkeys have receptive fields which are characterized by properties of binocularity, orientation selectivity and direction selectivity, and there is considerable physiological evidence that adjacent cells have similar stimulus requirements. Thus, the responses of cells recorded in close proximity to each other are dominated by input from the same eye and are driven optimally by stimuli of the same orientation 7. Anatomical evidence indicates that neurons with similar orientation preference and ocular dominance are arranged in two sets of columns which run throughout visual cortexT,8. Our study was designed to investigate whether cortical neurons are also organized according to a third response characteris- tic -- the preferred direction of movement of the stimulus. Single cell recording techniques were used to record from neurons in cat visual cortex. Details of the surgery and recording procedures have been described in detail previously 12. In brief, cats were anesthetized with 3~ halothane in 70~ nitrous oxide and 30~ oxygen and intubated with an endotracheal tube. The cats were paralyzed with 2 ml of Flaxedil and paralysis was maintained with an i.v. infusion of Flaxedil (1 ml/h) in 5 ~ lactated dextrose in Ringer (10 ml/h). Following topical application of neosynephrin and atropine, retinoscopy and appropriate powered contact lenses were used to focus the retina onto a tangent screen placed 57 cm from the eyes. A small hole was drilled in the skull overlying visual cortex and a platinum-iridium electrode was advanced into the cortex in small steps by means of a hydraulic microdrive. Action potentials from single units were amplified and monitored on an oscilloscope and a loud speaker. During the recording the halo- thane was discontinued and gaseous anesthesia was supplemented with Nembutal (1 mg/kg/h) 6. The cats' expired CO2 level and temperature were kept at normal levels.