Theories of Visual Mental Imagery (VMI) emphasize the processes of retrieval, modification, and recombination of sensory information from long-term memory. Yet, only few studies have focused on the behavioral mechanisms and neural correlates supporting VMI of stimuli from different semantic domains. Therefore, we currently have a limited understanding of how the brain generates and maintains mental representations of colors, faces, shapes - to name a few. Such an undetermined scenario renders unclear the organizational structure of neural circuits supporting VMI, including the role of the early visual cortex. We aimed to fill this gap by reviewing the scientific literature of five semantic domains: visuospatial, face, colors, shapes, and letters imagery. Linking theory to evidence from over 60 different experimental designs, this review highlights three main points. First, there is no consistent activity in the early visual cortex across all VMI domains, contrary to the prediction of the dominant model. Second, there is consistent activity of the frontoparietal networks and the left hemisphere's fusiform gyrus during voluntary VMI irrespective of the semantic domain investigated. We propose that these structures are part of a domain-general VMI sub-network. Third, domain-specific information engages specific regions of the ventral and dorsal cortical visual pathways. These regions partly overlap with those found in visual perception studies (e.g., fusiform face area for faces imagery; lingual gyrus for color imagery). Altogether, the reviewed evidence suggests the existence of domain-general and domain-specific mechanisms of VMI selectively engaged by stimulus-specific properties (e.g., colors or faces). These mechanisms would be supported by an organizational structure mixing vertical and horizontal connections (heterarchy) between sub-networks for specific stimulus domains. Such a heterarchical organization of VMI makes different predictions from current models of VMI as reversed perception. Our conclusions set the stage for future research, which should aim to characterize the spatiotemporal dynamics and interactions among key regions of this architecture giving rise to visual mental images.

中文翻译：

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视觉心理意象：异质神经结构的证据

视觉心理意象（VMI）理论强调从长期记忆中检索、修改和重组感觉信息的过程。然而，只有少数研究关注支持来自不同语义域的刺激的 VMI 的行为机制和神经相关性。因此，我们目前对大脑如何生成和维持颜色、面孔、形状等心理表征的了解有限。这种不确定的情况使得支持 VMI 的神经回路的组织结构变得不清楚，包括早期视觉皮层的作用。我们的目的是通过回顾五个语义领域的科学文献来填补这一空白：视觉空间、面部、颜色、形状和字母图像。这篇综述将理论与来自 60 多个不同实验设计的证据联系起来，强调了三个要点。首先，与主导模型的预测相反，所有 VMI 域的早期视觉皮层的活动并不一致。其次，无论研究的语义领域如何，在自愿 VMI 期间，额顶叶网络和左半球梭状回的活动都是一致的。我们建议这些结构是域通用 VMI 子网络的一部分。第三，特定领域的信息涉及腹侧和背侧皮质视觉通路的特定区域。这些区域与视觉感知研究中发现的区域部分重叠（例如，面部图像的梭形面部区域；彩色图像的舌回）。总而言之，审查的证据表明，VMI 存在通用域和特定域机制，选择性地与特定刺激属性（例如颜色或面孔）结合。这些机制将得到特定刺激领域子网络之间混合垂直和水平连接（异构）的组织结构的支持。这种 VMI 的异构组织做出了与当前 VMI 模型不同的预测，即反向感知。我们的结论为未来的研究奠定了基础，未来的研究目标应该是表征该架构关键区域之间的时空动态和相互作用，从而产生视觉心理图像。