Jackson P A, Kesner R P, Amann K
Department of Psychology, University of Utah, Salt Lake City, Utah, 84112, USA.
Neurobiol Learn Mem. 1998 Nov;70(3):328-48. doi: 10.1006/nlme.1998.3859.
In this task rats had to learn that a three-dimensional object stimulus (a rectangle) that was visible for 2 s would result in a positive (go) reinforcement for one object (a ball) and no reinforcement (no go) for a different object (a bottle). However, if the rectangle stimulus was visible for 8 s then there would be no reinforcement for the ball (no go), but a reinforcement for the bottle (go). After rats learned this conditional discrimination by responding differentially in terms of latency to approach the object, they received large (dorsal and ventral) lesions of the hippocampus, lesions of the medial prefrontal cortex (anterior cingulate and precentral cortex), lesions of the cortex dorsal to the dorsal hippocampus, or served as sham-operated controls. Following recovery from surgery they were retested. The results indicate that there were major impairments following hippocampal lesions, in contrast to cortical control and medial prefrontal cortex lesions, as indicated by smaller latency differences between positive and negative trials on postsurgery tests. In order to ensure that the deficits observed with hippocampal lesions were not due to a discrimination problem, new rats were trained in an object (gray cylinder) duration discrimination task. In this go/no go procedure, the rats were reinforced for a 2-s exposure (duration) of the gray cylinder, but not a 10-s duration, or vice versa. The results indicate that after hippocampal lesions, there was an initial deficit followed by complete recovery. There were no significant changes for the medial prefrontal, cortical control, or sham-operated animals. It appears that the hippocampus, but not the medial prefrontal cortex, is actively involved in representing in short-term memory temporal attribute information based on the use of markers for the beginning and end of the presence (duration) of a stimulus (object).
在这项任务中，大鼠必须学会，一个可见2秒的三维物体刺激（一个矩形）会对一个物体（一个球）产生正向（通过）强化，而对另一个不同物体（一个瓶子）不产生强化（不通过）。然而，如果矩形刺激可见8秒，那么对球不产生强化（不通过），但对瓶子产生强化（通过）。大鼠通过以接近物体的潜伏期差异做出不同反应来学会这种条件性辨别后，接受了海马体的大面积（背侧和腹侧）损伤、内侧前额叶皮质（前扣带回和中央前回皮质）损伤、海马体背侧上方皮质的损伤，或作为假手术对照组。手术后恢复后，对它们进行重新测试。结果表明，与皮质对照组和内侧前额叶皮质损伤相比，海马体损伤后存在严重损伤，手术后测试中正向和负向试验之间的潜伏期差异较小就表明了这一点。为了确保观察到的海马体损伤导致的缺陷不是由于辨别问题，对新的大鼠进行了物体（灰色圆柱体）持续时间辨别任务的训练。在这种通过/不通过程序中，大鼠在灰色圆柱体暴露2秒（持续时间）时得到强化，但在暴露10秒时不强化，反之亦然。结果表明，海马体损伤后，最初存在缺陷，随后完全恢复。内侧前额叶、皮质对照或假手术动物没有显著变化。似乎海马体，而不是内侧前额叶皮质，积极参与基于刺激（物体）存在（持续时间）开始和结束标记的短期记忆时间属性信息的表征。
