Floresco Stan B, Block Annie E, Tse Maric T L
Department of Psychology and Brain Research Centre, University of British Columbia, 2136 West Mall, Vancouver, B.C., Canada.
Behav Brain Res. 2008 Jun 26;190(1):85-96. doi: 10.1016/j.bbr.2008.02.008. Epub 2008 Feb 15.
The medial prefrontal cortex (mPFC) of the rat plays an essential role in behavioral flexibility, as lesions or inactivations of this region impair shifting between strategies or attentional sets using a variety of different behavioral tests. In the present study, we assessed the effects of inactivation of the mPFC on strategy set-shifting and reversal learning, using a novel, automated procedure conducted in an operant chamber. In Experiment 1, inactivation of the mPFC with bupivacaine did not impair the initial learning of a visual-cue (i.e.; always press the lever with a cue light illuminated above it) or a response (i.e.; always press the left lever) discrimination. Control rats required greater number of trials to shift from using a visual-cue to a response strategy than the opposite shift. mPFC inactivation impaired performance of a visual-cue-response set-shift, but not the easier response-visual-cue shift. In Experiment 2, pre-exposure to the visual-cue stimulus lights increased the difficulty of the response-visual-cue shift, reflected by a greater number of trials required by control rats to achieve criterion relative to those in Experiment 1. Under these conditions, inactivation of the mPFC did impair performance of this set-shift. In contrast, mPFC inactivation did not affect reversal learning of a response discrimination. These findings highlight the utility of this automated procedure for assessing set-shifting mediated by the mPFC. Furthermore, they reveal that the relative difficulty of the type of shift rats are required to perform has a direct impact on whether or not the mPFC contributes to this form of behavioral flexibility.
大鼠的内侧前额叶皮质（mPFC）在行为灵活性方面起着至关重要的作用，因为该区域的损伤或失活会通过各种不同的行为测试损害策略或注意力集之间的转换。在本研究中，我们使用在操作箱中进行的一种新颖的自动化程序，评估了mPFC失活对策略集转换和逆向学习的影响。在实验1中，用布比卡因使mPFC失活并不损害视觉线索（即：总是在其上方有提示灯亮起时按下杠杆）或反应（即：总是按下左侧杠杆）辨别任务的初始学习。与从反应策略转换到视觉线索策略相比，对照大鼠从使用视觉线索转换到反应策略需要更多的试验次数。mPFC失活损害了视觉线索-反应集转换的表现，但不影响较容易的反应-视觉线索转换。在实验2中，预先暴露于视觉线索刺激光增加了反应-视觉线索转换的难度，这表现为与实验1中的大鼠相比，对照大鼠达到标准需要更多的试验次数。在这些条件下，mPFC失活确实损害了这种集转换的表现。相比之下，mPFC失活并不影响反应辨别的逆向学习。这些发现突出了这种自动化程序在评估由mPFC介导的集转换方面的实用性。此外，它们揭示了大鼠需要执行的转换类型的相对难度对mPFC是否有助于这种行为灵活性形式有直接影响。
