Baxter M G, Holland P C, Gallagher M
Curriculum in Neurobiology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
J Neurosci. 1997 Jul 1;17(13):5230-6. doi: 10.1523/JNEUROSCI.17-13-05230.1997.
The attention directed to environmental stimuli can be modified by experience. For example, preexposure of a conditioned stimulus (CS) in the absence of reinforcement can retard subsequent conditioning of that stimulus when it is paired directly with an unconditioned stimulus, a phenomenon referred to as latent inhibition. Similarly, consistent pairings of a CS with another event can slow the acquisition of new information about that CS. Such phenomena suggest that reductions in the processing of CSs occur when they are made behaviorally irrelevant or consistent predictors of other events. On the basis of the observation that hippocampal lesions prevented such reductions in CS processing, we hypothesized that damage to basal forebrain cholinergic neurons that project to the hippocampus, using microinjections of the selective immunotoxin 192 IgG-saporin into the medial septum/vertical limb of the diagonal band (MS/VDB), also would disrupt normal reductions in CS processing. Lesions of hippocampal cholinergic input disrupted decreases in CS processing, manifested in both an absence of latent inhibition and a lack of reduced processing of a CS that had been a consistent predictor of another CS. These results indicate that cholinergic neurons in the MS/VDB play a role in the regulation of CS processing. Furthermore, these findings (in conjunction with previous findings) implicate both rostral (hippocampal-projecting) and caudal (cortical-projecting) regions of the basal forebrain cholinergic system in the modulation of attention.
对环境刺激的注意力可因经验而改变。例如,在无强化条件下对条件刺激(CS)进行预暴露,当该刺激随后直接与非条件刺激配对时,会延缓其后续的条件化过程,这一现象被称为潜伏抑制。同样,CS与另一事件的持续配对会减缓关于该CS的新信息的习得。这些现象表明,当CS在行为上变得无关紧要或成为其他事件的一致预测指标时,其加工过程会减少。基于海马损伤会阻止CS加工过程出现这种减少的观察结果,我们推测,通过向内侧隔核/斜角带垂直支(MS/VDB)微量注射选择性免疫毒素192 IgG-皂草素,破坏投射至海马的基底前脑胆碱能神经元,也会扰乱CS加工过程的正常减少。海马胆碱能输入的损伤破坏了CS加工过程的减少,表现为既无潜伏抑制,也不存在对曾是另一CS的一致预测指标的CS的加工减少。这些结果表明,MS/VDB中的胆碱能神经元在CS加工的调节中发挥作用。此外,这些发现(与先前的发现相结合)表明,基底前脑胆碱能系统的吻侧(投射至海马)和尾侧(投射至皮质)区域均参与注意力的调节。