Hand Dennis J, Fox Andrew T, Reilly Mark P
Central Michigan University, Department of Psychology, 101 Sloan Hall, Mount Pleasant, MI 48859, United States.
Behav Brain Res. 2006 Dec 15;175(2):337-42. doi: 10.1016/j.bbr.2006.09.001. Epub 2006 Oct 10.
The spontaneously hypertensive rat (SHR) has been shown to exhibit behavioral characteristics analogous to those exhibited by humans diagnosed with attention-deficit/hyperactivity disorder (ADHD). The present study was conducted to further evaluate the validity of the SHR model of ADHD by characterizing learning of a novel response under conditions of delayed reinforcement. Seven experimentally naïve SHRs and a control group of seven normotensive Wistar-Kyoto (WKY) rats were exposed to a contingency where one lever press initiated pellet delivery after a 15-s, resetting delay. Rats in both groups acquired lever pressing, and the pattern of acquisition was well described with a three-parameter, sigmoidal equation. Response acquisition was retarded in the SHRs; they took longer to acquire the behavior, exhibited lower response rates and earned fewer reinforcers over the course of the experiment. When reinforcer delivery was made immediate in a subsequent condition, the SHRs exhibited higher response rates than the WKY, suggesting that the lower rates of responding seen in the SHRs were due to the reinforcer delay. The results replicate previous research on response acquisition with delayed reinforcement and provide further validation of the SHR strain as a model of ADHD. Like humans diagnosed with ADHD, the SHRs appear to be hypersensitive to delayed consequences, which in the present context, interfered with learning a novel behavior.
自发性高血压大鼠（SHR）已被证明表现出与被诊断患有注意力缺陷多动障碍（ADHD）的人类相似的行为特征。本研究旨在通过在延迟强化条件下对一种新反应的学习进行特征描述，进一步评估ADHD的SHR模型的有效性。七只未经实验的SHR和七只正常血压的Wistar-Kyoto（WKY）大鼠组成的对照组被置于一种偶然情境中，即按下一个杠杆在15秒的重置延迟后会有食丸递送。两组大鼠都学会了按压杠杆，并且用一个三参数的S形方程很好地描述了习得模式。SHR的反应习得受到阻碍；它们花费更长时间来习得该行为，并在实验过程中表现出较低的反应率且获得的强化物更少。当在随后的条件下立即进行强化物递送时，SHR的反应率高于WKY，这表明在SHR中观察到的较低反应率是由于强化物延迟所致。这些结果重复了先前关于延迟强化下反应习得的研究，并进一步验证了SHR品系作为ADHD模型的有效性。与被诊断患有ADHD的人类一样，SHR似乎对延迟后果高度敏感，在当前情境中，这干扰了新行为的学习。
