Visuospatial attention in the rat and posterior parietal cortex lesions

Covert attention to visuospatial stimuli was assessed in rats using a modified version of a task designed for human subjects. Rats were trained to respond toward bright target lights presented to the right or left visual space. Dim cue lights served to attract their attention prior to the onset of the bright target lights. Consistent with previous research using similar paradigms, rats in this experiment displayed longer reaction times during trials in which the cue and target lights were presented on opposite sides of visual space. Throughout pre- and post-operative testing, individual subjects showed lateralized differences in the performance of this task as indicated by asymmetries in reaction time, the percentage of correct responses, and the number of responses made to each side of visual space (response bias). Lesioning the area of cortex thought to be a possible homolog of the posterior parietal cortex in primates produced no specific effects on performance. It is suggested that this paradigm may tap into an evolutionarily conserved attentional process, but that this process may be subserved by somewhat different neural structures in different species.