Plasticity of the guinea pig auditory cortex

本研究通过豚鼠听觉皮层单单位记录来探讨耳鸣的机制。在声音刺激的存在下，放电率增加，单个单位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中。我们观察到增加同步，但没有改变后，猫听觉皮层的耳鸣诱导药物（水杨酸盐或奎宁）的放电率。行为学结果表明，水杨酸或奎宁引起的耳鸣影响的区域的初级听觉皮层的特征频率为9-10 kHz，我们检查了该区域的听觉皮层的活动。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Wallace教授的支持下，我们最近使用Brain Ware记录了多达128个单位的豚鼠皮层活动。首先，我们测定了豚鼠听觉皮层的正常自发活动和刺激活动，正如Wallace教授所指出的，这些活动与猫的活动有些不同。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。肌肉注射奎宁引起的自发活动在9至10 kHz区域的初级听觉皮层没有显着的变化。然而，奎宁给药后同步性增加。这些结果表明，同步活动的增加与耳鸣的潜在机制有关。

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.