Behavioral variability, elimination of responses, and delay-of-reinforcement gradients in SHR and WKY rats
Behavioral variability, elimination of responses, and delay-of-reinforcement gradients in SHR and WKY rats
复制标题
DOI：
10.1186/1744-9081-3-60
复制
发表时间：
2007-11-20
影响因子：
5.1
通讯作者：
Sagvolden, Terje
中科院分区：
文献类型：
--
作者：
Johansen, Espen B.;Killeen, Peter R.;Sagvolden, Terje
背景：注意力缺陷/多动障碍(ADHD)的特征是注意力不集中、多动和冲动，这种模式是跨情景的、持续性的，并会导致社交和学习障碍。研究表明，ADHD患者的强化过程会发生改变。动态发展理论认为，强化延迟梯度的陡峭和行为消退的不足会导致ADHD的行为症状和行为变异性增加。方法：本研究以Wistar京都(WKY)大鼠为对照，研究了ADHD动物模型--自发性高血压大鼠(SHR)在习得过程中的行为变异性和非靶反应的消除。这项研究还旨在提供一种新的方法来测量SHR和WKY应变中的加固延迟梯度。这些动物在一个改装的操作室中进行了测试，提供了20种反应方案。在目标洞中的鼻子戳根据固定的加固间隔(FI)时间表产生水，而在剩余的19个洞中的鼻子戳要么没有后果，要么产生声音或房屋灯光的短暂闪烁。刺激产生孔被包括在内，以测试光和声在SHR中是否起到感觉强化的作用。前六次测试FI1 S的数据被用于计算反应的初始分布。此外，还计算了欧几里德距离(从每个洞的中心到目标洞中心的测量)和熵(变异性的度量)。通过将固定的时间间隔划分为历时，并确定一个历元中的反应的增强对下一个时间间隔的响应的贡献程度，计算了跨时段的增援延迟梯度。结果：在最初的六次训练中，行为聚集在靶洞周围。与WKY相比，SHR行为的初始变异性更大，无效反应的消除速度更慢。两种菌株对产生刺激的孔洞的利用几乎没有差别。对于SHR，强化的范围(强化的延迟梯度)被限制在前一秒，而对于WKY，它的延伸范围大约是WKY的四倍。结论：本研究结果支持先前的研究，表明相对于WKY对照组，SHR的行为变异性增加。一个可能相关的现象可能是在本研究中观察到的自发性高血压患者中非手术鼻戳的缓慢消除。这一发现支持了ADHD动态发展理论中提出的自发性高血压患者存在陡峭的强化延迟梯度。以更陡峭和更短的强化延迟梯度为特征的改变的强化过程可能定义ADHD的内表型。
Background: Attention-deficit/hyperactivity disorder (ADHD) is characterized by a pattern of inattention, hyperactivity, and impulsivity that is cross-situational, persistent, and produces social and academic impairment. Research has shown that reinforcement processes are altered in ADHD. The dynamic developmental theory has suggested that a steepened delay-of-reinforcement gradient and deficient extinction of behavior produce behavioral symptoms of ADHD and increased behavioral variability.Method: The present study investigated behavioral variability and elimination of non-target responses during acquisition in an animal model of ADHD, the spontaneously hypertensive rat (SHR), using Wistar Kyoto (WKY) rats as controls. The study also aimed at providing a novel approach to measuring delay-of-reinforcement gradients in the SHR and the WKY strains. The animals were tested in a modified operant chamber presenting 20 response alternatives. Nose pokes in a target hole produced water according to fixed interval (FI) schedules of reinforcement, while nose pokes in the remaining 19 holes either had no consequences or produced a sound or a short flickering of the houselight. The stimulus- producing holes were included to test whether light and sound act as sensory reinforcers in SHR.Data from the first six sessions testing FI 1 s were used for calculation of the initial distribution of responses. Additionally, Euclidean distance (measured from the center of each hole to the center of the target hole) and entropy (a measure of variability) were also calculated.Delay-of-reinforcement gradients were calculated across sessions by dividing the fixed interval into epochs and determining how much reinforcement of responses in one epoch contributed to responding in the next interval.Results: Over the initial six sessions, behavior became clustered around the target hole. There was greater initial variability in SHR behavior, and slower elimination of inefficient responses compared to the WKY. There was little or no differential use of the stimulus-producing holes by either strain. For SHR, the reach of reinforcement (the delay-of-reinforcement gradient) was restricted to the preceding one second, whereas for WKY it extended about four times as far.Conclusion: The present findings support previous studies showing increased behavioral variability in SHR relative to WKY controls. A possibly related phenomenon may be the slowed elimination of non-operant nose pokes in SHR observed in the present study. The findings provide support for a steepened delay-of-reinforcement gradient in SHR as suggested in the dynamic developmental theory of ADHD. Altered reinforcement processes characterized by a steeper and shorter delay-of-reinforcement gradient may define an ADHD endophenotype.