Spatial memory impairment in rats with fornix transection is not accompanied by a simple encoding deficit for directions of objects in visual space.
In Experiment 1, rats learned 6 discriminations among pairs of complex wide-angle visual displays, presented concurrently, using a computer-controlled Y maze. Fornix-transected rats were unimpaired relative to controls regardless of whether the displays comprised a single large "objectlike" figure or "scenelike" arrays of spatially distributed figures. Experiment 2 compared 2 versions of a visual discrimination in which either object identity (independent of location within the visual field) or location within the visual field (independent of object identity) had to be used. The fornix-transected rats performed normally with either cue. In Experiment 3, however, the same group was clearly impaired on a standard spatial memory test, spatial delayed nonmatching to sample. Although the fornix-transected rats were more likely to choose rapidly and inaccurately, their deficit was not a by-product of impulsive responding. The spatial impairment was not merely a difficulty in encoding direction of a single item within visual space, but more complex configural deficits could not be ruled out.
Gaffan
E A
EA
Department of Psychology, University of Reading, England.
Eacott
M J
MJ
D000818:Animals; D001288:Attention / Q000502:physiology*; D001931:Brain Mapping; D015350:Contrast Sensitivity / Q000502:physiology; D004193:Discrimination Learning / Q000502:physiology*; D006624:Hippocampus / Q000502:physiology*; D008326:Mammillary Bodies / Q000502:physiology*; D018782:Maze Learning / Q000502:physiology*; D011939:Mental Recall / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D009949:Orientation / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time / Q000502:physiology; D012153:Retention, Psychology / Q000502:physiology