Jinan Biomedicine R&D Center, School of Life Science and Technology, Jinan University , Guangzhou , People's Republic of China.
Department of Physiology, School of Life Science, China Medical University, Shenyang, Liaoning Province, People's Republic of China.
J Neurophysiol. 2019 Mar 1;121(3):785-798. doi: 10.1152/jn.00425.2018. Epub 2019 Jan 16.
Discriminating biologically relevant sounds is crucial for survival. The neurophysiological mechanisms that mediate this process must register both the reward significance and the physical parameters of acoustic stimuli. Previous experiments have revealed that the primary function of the auditory cortex (AC) is to provide a neural representation of the acoustic parameters of sound stimuli. However, how the brain associates acoustic signals with reward remains unresolved. The amygdala (AMY) and medial prefrontal cortex (mPFC) play keys role in emotion and learning, but it is unknown whether AMY and mPFC neurons are involved in sound discrimination or how the roles of AMY and mPFC neurons differ from those of AC neurons. To examine this, we recorded neural activity in the primary auditory cortex (A1), AMY, and mPFC of cats while they performed a Go/No-go task to discriminate sounds with different temporal patterns. We found that the activity of A1 neurons faithfully coded the temporal patterns of sound stimuli; this activity was not affected by the cats' behavioral choices. The neural representation of stimulus patterns decreased in the AMY, but the neural activity increased when the cats were preparing to discriminate the sound stimuli and waiting for reward. Neural activity in the mPFC did not represent sound patterns, but it showed a clear association with reward and was modulated by the cats' behavioral choices. Our results indicate that the initial auditory representation in A1 is gradually transformed into a stimulus-reward association in the AMY and mPFC to ultimately generate a behavioral choice. NEW & NOTEWORTHY We compared the characteristics of neural activities of primary auditory cortex (A1), amygdala (AMY), and medial prefrontal cortex (mPFC) while cats were performing the same auditory discrimination task. Our results show that there is a gradual transformation of the neural code from a faithful temporal representation of the stimulus in A1, which is insensitive to behavioral choices, to an association with the predictive reward in AMY and mPFC, which, to some extent, is correlated with the animal's behavioral choice.
区分有生物学意义的声音对于生存至关重要。介导这一过程的神经生理机制必须同时记录声音刺激的奖励意义和物理参数。先前的实验表明，听觉皮层（AC）的主要功能是提供声音刺激的声学参数的神经表示。然而，大脑如何将声音信号与奖励联系起来仍未解决。杏仁核（AMY）和内侧前额叶皮层（mPFC）在情绪和学习中起着关键作用，但尚不清楚 AMY 和 mPFC 神经元是否参与声音辨别，以及 AMY 和 mPFC 神经元的作用与 AC 神经元有何不同。为了研究这一点，我们在猫执行区分具有不同时程模式的声音的 Go/No-go 任务时，记录了初级听觉皮层（A1）、杏仁核和内侧前额叶皮层的神经元活动。我们发现 A1 神经元的活动忠实地编码了声音刺激的时程模式；这种活动不受猫的行为选择的影响。在 AMY 中，刺激模式的神经表示减少，但当猫准备辨别声音刺激并等待奖励时，神经活动增加。mPFC 中的神经活动不代表声音模式，但与奖励有明显的关联，并受到猫的行为选择的调节。我们的结果表明，A1 中的初始听觉表示逐渐转化为 AMY 和 mPFC 中的刺激-奖励关联，最终产生行为选择。
新的和值得注意的是，我们比较了猫在执行相同听觉辨别任务时初级听觉皮层（A1）、杏仁核（AMY）和内侧前额叶皮层（mPFC）的神经活动特征。我们的结果表明，从 A1 中对刺激的忠实时间表示的神经编码逐渐转变为与 AMY 和 mPFC 中预测奖励的关联，在某种程度上与动物的行为选择相关。
