DISCONNECTION OF MEDIAL AGRANULAR AND POSTERIOR PARIETAL CORTEX PRODUCES MULTIMODAL NEGLECT IN RATS

Two cortical areas in rats have been found to be important in directed attention and spatial processing: the medial agranular cortex (AGm), the rodent analog of the frontal eye fields; and the posterior parieta l cortex (PPC), the rodent analog of area 7 in primates. As in primate s, unilateral destruction of either of these cortical association area s produces severe contralesional neglect of visual, auditory, and tact ile stimulation. AGm and PPC are reciprocally interconnected by longit udinally oriented axons traveling in layer VI of the cortex. Their tra jectory provides a unique opportunity to examine the effects of discon nection of these two areas. The key question is whether these two regi ons function independently or as components of a cortical network for directed attention. Unilateral disconnection of the PPC and AGm was ac hieved via transverse knife-cuts extending through layer VI of cortex. and the disconnection verified by tract-tracing methods. The knife-cu ts produced severe multimodal neglect and allesthesia/allokinesia. The deficits produced by the knife-cuts were virtually identical to those produced by unilateral destruction of these regions. The control oper ates, which received knife-cuts that spared the interconnections betwe en the AGm and PPC, were unimpaired. The results indicate that AGm and PPC in rats function as parts of a cortical system for directed atten tion. (C) 1997 Elsevier Science B.V.