Plasticity of the guinea pig auditory cortex

本研究通过在豚鼠听觉皮层中进行单单元记录来检查耳鸣的机制。在声音刺激下，放电频率增加，单个单元的活动变得更加同步，这种变化也可能发生在耳鸣患者的听觉皮层。我们观察到猫听觉皮质在服用诱发耳鸣的药物（水杨酸盐或奎宁）后，同步性增强，但放电率没有变化。行为学结果表明，水杨酸或奎宁引起的耳鸣以9 ~ 10 kHz的特征频率影响初级听觉皮层区域，并对该区域的听觉皮层活动进行了检测。由于我们的外周听觉实验是在豚鼠身上进行的，我们也在豚鼠身上进行了皮层实验，以便直接比较外周和皮层数据，这与主要来自猫的可用皮层数据形成对比。在华莱士教授的支持下，我们最近用Brain Ware记录了多达128个单位的豚鼠皮层活动。首先，我们确定了豚鼠听觉皮层中正常的自发和受刺激的活动，正如华莱士教授所指出的，这与猫的听觉皮层有某种不同。其次，我们评估了耳鸣诱导药物（水杨酸盐和奎宁）对听觉皮层的影响。肌肉注射奎宁对初级听觉皮层9- 10khz区域的自发活动无显著影响。然而，服用奎宁后，同步性增加。这些结果表明，同步活动的增加与耳鸣的机制有关。

This study examined the mechanisms underlying tinnitus by making single-unit recordings in the guinea pig auditory cortex. The firing rate increased and the activity of individual single units became more synchronized in the presence of a sound stimulus, and such changes may also occur in the auditory cortex of a patient experiencing tinnitus. We observed increased synchronization but no change in firing rate after the administration of tinnitus-inducing drugs (salicylate or quinine) in cat auditory cortex. The behavioral results suggested that the tinnitus induced by administering salicylate or quinine affected the region of the primary auditory cortex with a characteristic frequency 9-10 kHz, and we examined the activity of the auditory cortex in this region. Because our peripheral auditory experiments were performed on guinea pigs, we also performed cortical experiments in guinea pigs in order to allow direct comparison between the peripheral and cortical data, which contrasts with the available cortical data mainly being from cat. With support from Professor Wallace, we recently recorded the guinea pig cortical activity in up to 128 single units using Brain Ware.Firstly, we determined the normal spontaneous and stimulated activities in the guinea pig auditory cortex, which, as suggested by Professor Wallace, differed somehow from those in cat. Secondly, we evaluated the effects of tinnitus-inducing drugs (salicylate and quinine) on the auditory cortex. Intramuscular administration of quinine induced no marked change in spontaneous activity in the 9-to 10-kHz region of the primary auditory cortex. However, synchronization was increased after the administration of quinine. These results suggest that increased synchronization activity is related to the mechanisms underlying tinnitus.