Bang Ji Won, Chan Russell W, Parra Carlos, Murphy Matthew C, Schuman Joel S, Nau Amy C, Chan Kevin C
Department of Ophthalmology, NYU Grossman School of Medicine, NYU Langone Health, New York University, New York, NY 10017, USA.
Department of Radiology, Mayo Clinic, Rochester, MN 55905, USA.
Brain Commun. 2023 Apr 11;5(2):fcad119. doi: 10.1093/braincomms/fcad119. eCollection 2023.
Plasticity in the brain is impacted by an individual's age at the onset of the blindness. However, what drives the varying degrees of plasticity remains largely unclear. One possible explanation attributes the mechanisms for the differing levels of plasticity to the cholinergic signals originating in the nucleus basalis of Meynert. This explanation is based on the fact that the nucleus basalis of Meynert can modulate cortical processes such as plasticity and sensory encoding through its widespread cholinergic projections. Nevertheless, there is no direct evidence indicating that the nucleus basalis of Meynert undergoes plastic changes following blindness. Therefore, using multiparametric magnetic resonance imaging, we examined if the structural and functional properties of the nucleus basalis of Meynert differ between early blind, late blind and sighted individuals. We observed that early and late blind individuals had a preserved volumetric size and cerebrovascular reactivity in the nucleus basalis of Meynert. However, we observed a reduction in the directionality of water diffusion in both early and late blind individuals compared to sighted individuals. Notably, the nucleus basalis of Meynert presented diverging patterns of functional connectivity between early and late blind individuals. This functional connectivity was enhanced at both global and local (visual, language and default-mode networks) levels in the early blind individuals, but there were little-to-no changes in the late blind individuals when compared to sighted controls. Furthermore, the age at onset of blindness predicted both global and local functional connectivity. These results suggest that upon reduced directionality of water diffusion in the nucleus basalis of Meynert, cholinergic influence may be stronger for the early blind compared to the late blind individuals. Our findings are important to unravelling why early blind individuals present stronger and more widespread cross-modal plasticity compared to late blind individuals.
大脑可塑性受个体失明起始年龄的影响。然而，驱动不同程度可塑性的因素在很大程度上仍不清楚。一种可能的解释将不同水平可塑性的机制归因于源自梅纳特基底核的胆碱能信号。这一解释基于以下事实：梅纳特基底核可通过其广泛的胆碱能投射来调节诸如可塑性和感觉编码等皮质过程。然而，没有直接证据表明梅纳特基底核在失明后会发生可塑性变化。因此，我们使用多参数磁共振成像，研究了梅纳特基底核的结构和功能特性在早期失明、晚期失明和视力正常个体之间是否存在差异。我们观察到，早期和晚期失明个体的梅纳特基底核体积大小和脑血管反应性得以保留。然而，与视力正常个体相比，我们观察到早期和晚期失明个体的水扩散方向性均有所降低。值得注意的是，梅纳特基底核在早期和晚期失明个体之间呈现出不同的功能连接模式。在早期失明个体中，这种功能连接在全局和局部（视觉、语言和默认模式网络）水平上均得到增强，但与视力正常对照组相比，晚期失明个体几乎没有变化。此外，失明起始年龄可预测全局和局部功能连接。这些结果表明，在梅纳特基底核水扩散方向性降低的情况下，与晚期失明个体相比，胆碱能影响对早期失明个体可能更强。我们的研究结果对于揭示为何早期失明个体比晚期失明个体表现出更强且更广泛的跨模态可塑性具有重要意义。
