Bradshaw C M
Division of Psychiatry, University of Nottingham, UK.
Behav Processes. 2018 Dec;157:562-569. doi: 10.1016/j.beproc.2018.04.017. Epub 2018 Apr 25.
Rats were trained under a discrete-trials adjusting-magnitude schedule in which a response on lever A delivered either a larger or a smaller sucrose reinforcer (q = 8 μl, q = 64 μl) with equal probability, while a response on B delivered a reinforcer whose size q was adjusted according to the rats' choices. When A was preferred in a given block of trials, q was increased in the following block; when B was preferred, q was reduced in the following block. The oscillating changes in q, analysed by the Fourier transform, could be described by a power spectrum whose dominant frequency corresponded to a period of 40-50 trial blocks. The equilibrium value of q (q) was inversely related to sucrose concentration; it significantly exceeded the arithmetic mean of q and q when the concentration was 0.2 or 0.4 M, but not when it was 0.8 or 1.6 M. Analysis by mixed-effects modelling revealed a trend for the power of oscillation of q to increase monotonically with sucrose concentration; the period of oscillation was not systematically related to sucrose concentration. These results are consistent with predictions derived from a revised version of the multiplicative hyperbolic model of intertemporal choice.
大鼠在离散试验调整幅度的实验安排下接受训练，即在杠杆A上做出反应时，有同等概率获得较大或较小的蔗糖强化物（q = 8微升，q = 64微升），而在杠杆B上做出反应时，获得的强化物大小q会根据大鼠的选择进行调整。在给定的试验块中，如果大鼠偏好A，那么在下一个试验块中q会增加；如果偏好B，那么在下一个试验块中q会降低。通过傅里叶变换分析q的振荡变化，可以用一个功率谱来描述，其主导频率对应于40 - 50个试验块的周期。q的平衡值（q̅）与蔗糖浓度呈负相关；当浓度为0.2或0.4 M时，它显著超过q和q̅的算术平均值，但当浓度为0.8或1.6 M时则不然。通过混合效应模型分析发现，q的振荡功率有随蔗糖浓度单调增加的趋势；振荡周期与蔗糖浓度没有系统的相关性。这些结果与从跨期选择的乘法双曲线模型的修订版得出的预测一致。
