Cross-modal transfer effects on visual discrimination depends on lesion location in the rat visual system.

The effects of postoperative visual and auditory training on a brightness discrimination task were examined after lesions of various structures in the visual system. In Experiment 1, rats were trained to avoid shock with visual intensity cues. Twenty-four hours later, each rat received bilateral lesions in one of the following areas of the visual system: (1) sham, (2) visual cortex (VC), (3) pretectal (PT) area, (4) combined PT/VC, (5) superior colliculus (SC), or (6) combined SC/VC. Six days later, each rat received either training with visual or auditory intensity cues, or no training. The next day all rats were retrained on the preoperative visual avoidance task. All lesions except those in the SC condition produced relearning deficits. Auditory training reduced these deficits significantly more than visual training, except in rats with combined SC/VC lesions. In Experiment 2, sham and combined PT/VC lesion rats were given either direct or reversal intensity training using visual or auditory cues before relearning the visual discrimination. Rats given auditory direct training relearned the task faster than rats given reversal training or visual direct training. Postinjury training with an intact sensory system can enhance functional recovery more effectively than training with the damaged system. The differential effects of direct and reversal training suggest that cross-modal training involves both specific and nonspecific transfer that may be mediated through the VC or the SC.