A COMPARISON OF HEMISPATIAL NEGLECT FROM POSTERIOR PARIETAL AND PERIARCUATE LESIONS IN THE MONKEY

In this experiment, we examined hemispatial neglect in the monkey, com paring unilateral parietal lesions with lesions of frontal cortex. Our purpose was to resolve the apparent puzzle of grave parietal symptoms in humans shown only inconsistently in monkeys. We quantitatively com pared visual neglect and recovery in monkeys with unilateral posterior parietal, periarcuate, and principal sulcus (control) lesions. Neocor tical lesions of these three regions were produced in 9 macaque monkey s, and they were tested for their ability to detect and respond to bri ef visual stimuli in varying field eccentricities. Both parietal and a rcuate lesions resulted in neglect. Recovery from the arcuate lesion o ccurred by the 3rd postoperative week, but neglect was strongly eviden t in the parietal animals in the 8th week. A second homologous lesion produced a more severe and enduring neglect of contralateral stimuli a nd also reinstated neglect in the hemifield affected by the first lesi on. These data confirm symptoms of visual neglect from parietal lesion s and are consistent with differentiated functions of posterior pariet al and arcuate cortex in spatial attention.