SPATIAL-RELATED AND LOCOMOTION-RELATED NEURAL REPRESENTATION IN RAT HIPPOCAMPUS FOLLOWING LONG-TERM SURVIVAL FROM ISCHEMIA

Spatial and locomotion-related behavioral correlates of hippocampal ce ll discharge were compared between ischemic and sham-control rats perf orming a spatial maze. Ischemic rats showed impaired choice accuracy d uring maze acquisition, but not during asymptote performance. Single-u nit correlates during asymptote performance revealed enhanced spatial selectivity of CA2/3 complex-spike cells coincident with attenuated pl ace-specific firing by hilar complex-spike or subicular cells. Respons ivity to locomotion state by stratum granulosum interneurons was exagg erated, and locomotion-induced changes in firing of hilar and subicula r interneurons was reduced. Ischemic rats showed recovered spatial lea rning abilities as evidenced by the fact that acquisition of the spati al task in a second environment was not impaired. Because representati onal reorganization was also observed in ischemic, maze-naive rats, br ain injury per se appears to change information coding schemes.