Comparisons of hemi-inattention produced by unilateral lesions of the posterior parietal cortex or medial agranular prefrontal cortex in rats: neglect, extinction, and the role of stimulus distance.

Neglect in human and non-human primates has been demonstrated following unilateral lesions of both posterior parietal and prefrontal areas. While it has now been well established that a unilateral lesion of the rodent analog of dorsolateral prefrontal cortex, medial agranular cortex (AGm), results in neglect, the effects of unilateral damage restricted to rodent posterior parietal cortex (PPC) have not been examined in detail. The current study assessed rats with unilateral lesions of PPC or AGm on their ability to orient to unilateral and bilateral stimulation. Since it has been proposed in both the primate and rodent literatures that frontal areas may be responsible for the perception of near space while parietal areas may be responsible for far space, stimuli were presented at two different distances. Lesions of PPC and AGm resulted in severe neglect relative to control operates, with both PPC and AGm operates manifesting severe hemi-inattention and allesthesia relative to control operates. After behavioral recovery from neglect there was no evidence of extinction to bilateral simultaneous stimulation. While neglect to visual stimuli predominated in unilateral PPC operates, unilateral AGm operates had severe neglect in all modalities. In addition, while both left and right PPC operates showed contralesional neglect, AGm operates demonstrated the lateralized differences in neglect reported in previous studies. All groups demonstrated an approximately equivalent level of neglect to stimuli presented at the two different distances, and thus failed to support the suggestion of a peripersonal-extrapersonal dichotomy between frontal and parietal areas in rodents.