A COMPUTER-CONTROLLED MAZE ENVIRONMENT FOR TESTING VISUAL MEMORY IN THE RAT

A computer-controlled version of a Y-maze was developed to allow autom ated testing of rats' learning and memory with visual stimuli. Each of the 3 arms terminated with 2 adjacent monochromatic screens, 43 cm fr om the maze centre, providing a total stimulus area 47 cm wide by 18.5 cm high. The displays were abstract patterns extending across 2 scree ns, generated by algorithms which provided a large pool of discriminab le patterns. The patterns used were of 2 general classes: Scenes (inte rnally complex patterns with varying numbers of foreground shapes dist ributed across contrasted backgrounds) and Objects (internally homogen eous single figures, confined to the central part of the display). The y could be stationary or have oscillatory movement. Subjects' location in the maze was monitored by infrared beam photodetectors; approach t o correct patterns was rewarded with food. Pigmented rats of the Hoode d Lister and Dark Agouti strains were tested. All could acquire 2-pair concurrent visual discriminations comprising 2 positive and 2 negativ e patterns, either Scenes or Objects; most could acquire 4-pair discri minations. Dark Agouti rats generally performed better than Hooded Lis ters. A novel training procedure using one positive and many negative patterns resulted in rapid learning of novel discriminations with eith er moving or non-moving patterns. The apparatus is an effective enviro nment for visual learning by rats, suitable for a wide range of tasks in neuropsychology and psychopharmacology.