Department of Experimental Psychology, Complutense University of Madrid, Madrid, Spain.
Centre for Cognitive and Computational Neuroscience, Madrid, Spain.
PLoS Comput Biol. 2023 Aug 3;19(8):e1011007. doi: 10.1371/journal.pcbi.1011007. eCollection 2023 Aug.
The thalamus is a central brain structure that serves as a relay station for sensory inputs from the periphery to the cortex and regulates cortical arousal. Traditionally, it has been regarded as a passive relay that transmits information between brain regions. However, recent studies have suggested that the thalamus may also play a role in shaping functional connectivity (FC) in a task-based context. Based on this idea, we hypothesized that due to its centrality in the network and its involvement in cortical activation, the thalamus may also contribute to resting-state FC, a key neurological biomarker widely used to characterize brain function in health and disease. To investigate this hypothesis, we constructed ten in-silico brain network models based on neuroimaging data (MEG, MRI, and dwMRI), and simulated them including and excluding the thalamus, and raising the noise into thalamus to represent the afferences related to the reticular activating system (RAS) and the relay of peripheral sensory inputs. We simulated brain activity and compared the resulting FC to their empirical MEG counterparts to evaluate model's performance. Results showed that a parceled version of the thalamus with higher noise, able to drive damped cortical oscillators, enhanced the match to empirical FC. However, with an already active self-oscillatory cortex, no impact on the dynamics was observed when introducing the thalamus. We also demonstrated that the enhanced performance was not related to the structural connectivity of the thalamus, but to its higher noisy inputs. Additionally, we highlighted the relevance of a balanced signal-to-noise ratio in thalamus to allow it to propagate its own dynamics. In conclusion, our study sheds light on the role of the thalamus in shaping brain dynamics and FC in resting-state and allowed us to discuss the general role of criticality in the brain at the mesoscale level.
丘脑是大脑的一个中枢结构，作为从外周向皮层传递感觉输入的中继站，并调节皮层觉醒。传统上，它被认为是一种被动的中继站，在脑区之间传递信息。然而，最近的研究表明，丘脑在基于任务的背景下也可能在塑造功能连接（FC）方面发挥作用。基于这一观点，我们假设由于其在网络中的中心地位及其在皮层激活中的参与，丘脑也可能对静息状态 FC 做出贡献，静息状态 FC 是一种广泛用于描述健康和疾病中大脑功能的关键神经生物学标志物。为了验证这一假设，我们构建了基于神经影像学数据（MEG、MRI 和 dwMRI）的十个脑网络模型，并模拟了包括和不包括丘脑的模型，以及提高丘脑的噪声来代表与网状激活系统（RAS）相关的传入和外周感觉输入的中继。我们模拟了脑活动，并将得到的 FC 与它们的经验 MEG 对应物进行比较，以评估模型的性能。结果表明，具有更高噪声的丘脑的分区版本，能够驱动阻尼的皮层振荡器，增强了与经验 FC 的匹配。然而，当引入丘脑时，对于已经活跃的自激皮层，其动力学没有受到影响。我们还证明了增强的性能与丘脑的结构连接无关，而是与它更高的噪声输入有关。此外，我们强调了丘脑的信号与噪声比的平衡在允许其传播自身动力学方面的重要性。总之，我们的研究揭示了丘脑在静息状态下塑造大脑动力学和 FC 中的作用，并使我们能够讨论临界性在脑的介观水平上的一般作用。
