Pachitariu Marius, Lyamzin Dmitry R, Sahani Maneesh, Lesica Nicholas A
Gatsby Computational Neuroscience Unit, and.
Ear Institute, University College London, London WC1E 6BT, United Kingdom, and Graduate School of Systemic Neurosciences, Ludwig-Maximilians-University Munich, 80802 Munich, Germany.
J Neurosci. 2015 Feb 4;35(5):2058-73. doi: 10.1523/JNEUROSCI.3318-14.2015.
Sensory function is mediated by interactions between external stimuli and intrinsic cortical dynamics that are evident in the modulation of evoked responses by cortical state. A number of recent studies across different modalities have demonstrated that the patterns of activity in neuronal populations can vary strongly between synchronized and desynchronized cortical states, i.e., in the presence or absence of intrinsically generated up and down states. Here we investigated the impact of cortical state on the population coding of tones and speech in the primary auditory cortex (A1) of gerbils, and found that responses were qualitatively different in synchronized and desynchronized cortical states. Activity in synchronized A1 was only weakly modulated by sensory input, and the spike patterns evoked by tones and speech were unreliable and constrained to a small range of patterns. In contrast, responses to tones and speech in desynchronized A1 were temporally precise and reliable across trials, and different speech tokens evoked diverse spike patterns with extremely weak noise correlations, allowing responses to be decoded with nearly perfect accuracy. Restricting the analysis of synchronized A1 to activity within up states yielded similar results, suggesting that up states are not equivalent to brief periods of desynchronization. These findings demonstrate that the representational capacity of A1 depends strongly on cortical state, and suggest that cortical state should be considered as an explicit variable in all studies of sensory processing.
感觉功能是由外部刺激与内在皮质动力学之间的相互作用介导的，这在皮质状态对诱发反应的调制中很明显。最近跨不同模态的多项研究表明，神经元群体的活动模式在同步和去同步皮质状态之间可能有很大差异，即在存在或不存在内在产生的上行和下行状态时。在这里，我们研究了皮质状态对沙鼠初级听觉皮层（A1）中音调与语音群体编码的影响，发现同步和去同步皮质状态下的反应在性质上有所不同。同步A1中的活动仅受到感觉输入的微弱调制，音调与语音诱发的尖峰模式不可靠，且局限于一小范围的模式。相比之下，去同步A1中对音调与语音的反应在各次试验中在时间上精确且可靠，不同的语音片段诱发了具有极低噪声相关性的多样尖峰模式，使得反应能够以近乎完美的准确度被解码。将对同步A1的分析限制在上行状态内的活动产生了类似结果，表明上行状态不等同于短暂的去同步期。这些发现表明，A1的表征能力强烈依赖于皮质状态，并表明在所有感觉处理研究中都应将皮质状态视为一个明确的变量。
