The effect of familiarity on distraction and single cue use after hippocampal damage.
Spatial disorientation frequently occurs in conditions such as Alzheimer's disease that damage the hippocampus, a brain structure necessary for learning and memory. Use of a single cue to mark a submerged escape platform in the Morris water test can reduce spatial disorientation in rats. If the cue used is a familiar one, disoriented rats perform the wayfinding task as well as control animals. However, in a real-world environment, cues rarely occur alone. This study examined whether rats with bilateral hippocampal lesions familiar with a cue performed the Morris water test as well as controls and faster than lesioned rats unfamiliar with the cue when a distracter was present. Bilateral electrolytic lesions were made in male rats that had received either familiarity with a cue or handling only. Familiar lesioned rats were introduced to the distracter on test days 1 (FB1) or 3 (FB3), and unfamiliar lesioned rats on day 3 (UB3). No significant differences were found for FB1 or FB3 rats and their respective controls. FB1 rats increased mean swim times on day 1 compared to preoperative day 4 (16.44 +/- 4.3 vs. 4.06 +/- 2.1 s, respectively, p < 0.03) but quickly adapted to the distracter. FB3 rats were slower than FB1 rats on day 3 (6.81 +/- 1.0 vs. 4.56 +/- 0.3 s, respectively, p < 0.05). UB3 rats were impaired on the task compared to FB1 rats on days 3-7 (p < 0.05). These findings suggest that cue familiarity is effective in the presence of a distracter and that the response of disoriented rats to a distracter is influenced by the amount of prior experience with the cue.
College of Nursing, University of Illinois at Chicago, USA.
J E
JE
Holden
B
B
Therrien
D000704:Analysis of Variance; D000818:Animals; D001288:Attention; D003221:Confusion / Q000209:etiology* / Q000517:prevention & control*; D003463:Cues; D004195:Disease Models, Animal; D006624:Hippocampus / Q000293:injuries*; D008297:Male; D018782:Maze Learning; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012678:Sensation Disorders / Q000209:etiology* / Q000517:prevention & control*; D013028:Space Perception; D013997:Time Factors