Neglect following unilateral ablation of the caudal but not the rostral portion of medial agranular cortex of the rat and the therapeutic effect of apomorphine

Abstract

The medial agranular cortex (AGm) of the rat is often considered analogous to the frontal eye field (FEF) of the monkey. However, recent anatomical, physiological, and behavioral evidence indicates that, while the caudal portion of AGm may indeed be an analog of the primate FEF, the rostral portion of AGm may be more similar to the primate supplementary motor area. The current study examined the effects of unilateral ablation of both the rostral and caudal components of AGm on the ability to orient to unilaterally presented stimuli. As expected, lesions of caudal but not rostral AGm resulted in a severe unilateral neglect of stimuli characteristic of rats with lesions of the entire rostral-caudal extent of AGm and of monkeys with FEF lesions. Caudal AGm operates also had more severe neglect than a group of rats from a previous study with larger AGm lesions which damaged the caudal portion of AGm to varying degrees. In addition, a second study showed the dopamine agonist apomorphine to have an acute dose-dependent therapeutic effect on the neglect resulting from caudal AGm ablation similar to that seen in animals with ablation of the entire rostral-caudal extent of AGm.