Functional identification of synaptic plasticity in the rat auditory cortex

在这项研究中，我们研究了突触可塑性在大鼠听皮层中的生理作用。我们研究了长期抑郁(LTD)。内侧膝状体传入锥体神经元的突触呈LTD，对NMDA受体拮抗剂敏感。相反，LTD对皮质锥体神经元之间突触中的代谢性谷氨酸受体拮抗剂敏感。我们进一步研究了长时程增强(LTP)的序列依赖特性。这种序列依赖性是在秒的尺度上观察到的，因此LTP只在较早刺激的突触中观察到。在M胆碱受体拮抗剂存在下，LTP的序列依赖性被取消。内源性胆碱能的重要性也体现在行为分析的大鼠的声音序列辨别能力上。这些结果表明，序列依赖的LTP可能在听觉皮质的时间信息处理中发挥作用。最后，我们研究了听觉大脑皮层和高级大脑皮层之间的特性。初级感觉皮层可以通过记忆回忆或想象，通过来自高级皮层的反馈投射来激活。我们在大鼠脑片上研究了听皮质与18a区之间的皮质边界的性质。刺激18a区通常不会引起听觉皮质的活动。然而，在多次交替刺激18a区和听觉皮质后，18a区触发的多突触反馈活动侵犯了整个听觉皮质。我们的发现表明，根据之前的活动，不同的大脑皮层区域很快就会与反馈活动绑定在一起。

In this study, we investigated the physiological roles of synaptic plasticity in the rat auditory cortex. We studied long-term depression (LTD). The synaptic inputs to pyramidal neurons from the medial geniculate body exhibited LTD, which was sensitive to an antagonist of NMDA receptors. In contrast, LTD was sensitive to an antagonist of metabotropic glutamate receptors in the synapses between cortical pyramidal neurons. We further investigated sequence-dependent properties of long-term potentiation (LTP). The sequence-dependence was observed on the scale of seconds, so that LTP was observed only in the synapses stimulated earlier. The sequence-dependence of LTP was abolished in the presence of antagonists of muscarinic acetylcholine receptors. The importance of endogenous cholinergic was also shown in the sound-sequence discrimination ability of rats using behavioral analyses. These results suggest that the sequence-dependent LTP may have a role in temporal information processing in the auditory cortex. Finally, we investigated the properties between the auditory cortex and higher cortices. Primary sensory cortices can be activated by memory recall or imagery via feedback projections from higher cortices. We studied the properties of the cortical boundary between the auditory cortex and area 18a in rat cerebral slices. Activities in the auditory cortex were usually not elicited by the stimulation of area 18a. However, the whole auditory cortex was invaded by polysynaptic feedback activities triggered in area 18a, after area 18a and the auditory cortex were alternately stimulated several times. Our findings indicate that different cortical areas are quickly bound with feedback activities depending on previous activities.